BETA-DECAYSPECTROSCOPYOFNEUTRONRICHISOTOPESUSINGAPLANARGERMANIUMDOUBLE-SIDEDSTRIPDETECTORByNicoleLarsonADISSERTATIONSubmittedtoMichiganStateUniversityinpartialoftherequirementsforthedegreeofChemistryŒDoctorofPhilosophy2016ABSTRACTBETA-DECAYSPECTROSCOPYOFNEUTRONRICHISOTOPESUSINGAPLANARGERMANIUMDOUBLE-SIDEDSTRIPDETECTORByNicoleLarsonOneimportantoverarchinggoalinnuclearscienceistheexperimentalinvestigationofnuclearstructure.Understandinghowthestructureofthenucleusevolvesasmoreneutrons(N)andpro-tons(Z)areaddedisvitaltoprobingthemechanismsthatdrivetheevolutionofshellstructure.Onetooltoinvestigatethemigrationofenergylevelsalongisotopicchainsisthroughthecharac-terizationofisomericstates.Isomericstatescansignalatransitionbetweenverydifferentnuclearandthereforecanbeanimportanttestoftheevolutionofnuclearstructure.b-decayspectroscopyisusedtoprovideawealthofinformationonexoticisotopesincludinghalf-lives,branchingratios,andenergylevels.Theselectivityprovidedbydecayspectroscopyplacesconstraintsonthespinsandparitiesofnuclearlevels.RecentlyanewplanarGermaniumDouble-SidedStripdetector(GeDSSD)hasbeenusedindecayspectroscopyexperimentsattheNationalSuperconductingCyclotronLaboratory(NSCL).Exoticionsareproduced,deliveredto,andstoppedwithintheGeDSSD,wheretheb-decayelectrons,conversionelectronsandgraysaredetected.Inthepresentwork,theelectronandgraydetectionefoftheGeDSSDweredeterminedwithsourcemeasurementsandtheperformanceoftheGeDSSDwithradioactiveionswascharacterizedinmultipleexperimentsandincludedb-decaycorrelationefb-gammasummingcorrections,andchargestateseparationthroughTotalKineticEnergy(TKE)measurements.FollowingthedevelopmentoftheGeDSSD,itwasappliedheretotheA˘110regiontoexplorelow-energyisomericstates.Nucleiinthisregionhavehadindicationsofchangingnuclearshapesasafunctionofnucleonnumberformanyyears,andmuchtheoreticalworkhasbeendoneinanattempttoexplaintheexistingexperimentaldata.Thetheoreticalcalculationspredictachangesinstructureasafunctionofnucleonnumber,anddataisneededtoclarifytheunderstandingoftheregion.ThesearchforisomericstatesisonemethodbywhichthenuclearstructureoftheregioncanbeMeasuringconversioncoefofnucleartransitionscanconstrainthemultipolarityoftheisomerictransition,whichinturncanconstrainthespinsandparitiesoftheinitialandstates.Inordertoaddressthisneedfordata,arecentNSCLb-decayexperimentfocusedonseveralA˘110nucleiwithZrangingfrom41to46andtheresultsarepresentedhere.Inparticular,thisworkdiscussesanisomericstatein115Ruat123.8keV,whichwaspreviouslyplacedatanunknownenergy.ThisisomericstateisoneofseveralisomersintheRuandPdisotopicchains,likelyarisingfromtheh11=2orbital.Additionally,severalshort-lived(lessthan20ms)isomericstatesin118Ag,107Mo,and109Moarediscussed.ACKNOWLEDGEMENTSTherearemanyindividualswhohavesupportedmewhileIhaveworkedonmyPhD.First,Iwouldliketothankmyadviser,SeanLiddick,forallhishelpandsupport.Iwouldalsolikethethankthemembersofmycommittee,DaveMorrissey,PaulMantica,andHendrickSchatz,fortheirhelp.Additionally,Ishouldthankthemembersofmygroup,allofwhomhavehelpedandsupportedme.Scott,youwerealwaysabighelp,andIappreciateallyou'vedoneforme.Chris,yourtechnicalknow-howwasalwaysahelp.ThetwoofyouwillalwaysbewhatIthinkofasthefioriginalflbgroup.IoweabigthankstoourpostdocBen,whoIthinkhasbeenofgreathelptoeveryoneinourgroup.Andtothefinewflbgroupmemberswhohavestartedworkingonthenewdirectionofthegroupwiththeb-Oslomethod,BeckyandKatie,whileweweren'tworkingonthesametopics,thankyouforyourmoralsupportandyourfriendship.Thereweremanypeopleatthelabwhohelpedwithmakingmythesisexperimentrunsmoothly.ThankyoutoalltheoperatorswhomadesurewehadbeamandtotheA1900group,inparticularTomGinter,fortheirhelpwithselectingtheionsforustostudy.Anotherlargethankyougoestoallofthepeoplewhohelpedwiththesetupandwhosatshift.Ifthere'sanyoneIforgot,Iapologizeprofusely.Finally,thereareseveralotherpeoplewhohavesupportedmewhileIwasinschool.Myfamilywasalwayssupportive.Imademanygreatfriendsduringgradschool,withoutwhomIcouldn'thavemadeitthrough.Aimee-thanksforbeingagreatroommateformyfewyearshere,andthenagreatneighbor!Itwon'tbethesamewithoutmyweeklymurdermysterywithyouandBill.ThankstoSteve,Scott,Luke,Jayda,andZachforbeingtherefromthebeginning.Itcertainlyhelpedtomeetsuchgreatpeoplesoquickly.Thankyou,Sasha,forourlunchdatesandventingsessionsaboutChemistrygradschool!Itseemsappropriatethatwebothstartedatthesametime,andthendefendedwithindaysofeachother.ThankyouJenna,Ragnar,andTitusforalwaysorganizingfuneventslikehappyhour,theprogressive,anddanceparties!Finally,thankyoutoAndrew,forbecomingsuchalargepartofmylifeinthelastfewmonths.You'vebeenagreativsourceofsupport(andagreatdistractionwhenIneededitfromthesisstuff).Therearesomanyotherpeoplewhohavebeenapositivepresenceinmylifeduringgradschool,andwhileIdon'thavespacetolisteveryonebyname,Iwanttothankeachandeveryoneofyouforyoursupport.vTABLEOFCONTENTSLISTOFTABLES.......................................ixLISTOFFIGURES.......................................xiCHAPTER1INTRODUCTION...............................11.1Nuclearstructureandisomerspectroscopy......................11.1.1b-decayspectroscopy.............................21.1.2Techniqueintroduction............................21.2Applicationofb-decayandisomerspectroscopytoA˘110nuclei.........21.2.1Shellmodelintroduction...........................31.2.2Ruisotopes..................................51.2.2.1Previousexperimentalresults...................71.2.2.2Theoreticalpredictions.......................111.3Dissertationoutline..................................12CHAPTER2TECHNIQUE.................................142.1Introduction......................................142.2b-decayspectroscopy................................142.2.1bdecay....................................142.2.2b-decayselectionrules............................162.3Electromagnetictransitions..............................172.3.1gdecay....................................172.3.2InternalConversion..............................182.4b-decayspectroscopyexperimentaldesign......................20CHAPTER3GERMANIUMDOUBLE-SIDEDSTRIPDETECTOR...........233.1Introduction......................................233.2Hardware.......................................233.3Energycalibrations..................................243.3.1Energyextractiontechniques.........................243.3.2High-gainenergycalibration.........................263.3.2.1Commissioningrunse11503ande09055.............263.3.2.2e11003...............................303.3.2.3Re-analysisofe11503.......................353.3.3Low-gainenergycalibration.........................383.3.3.1Commissioningrunse11503ande09055.............383.3.3.2e11003...............................393.4Ef......................................473.4.1Absolutegrayefy...........................473.4.2Electronefy..............................493.4.2.1Electrondetectionefy....................493.4.2.2b-decayelectroncorrelationefy..............51vi3.5b-decayspectroscopytechniques...........................533.5.1Triggering...................................533.5.2Eventlocalization...............................543.6b-gSumming.....................................583.6.1Developmentoftechniqueinsimulation...................583.6.2Applicationoftechniqueindata.......................623.7Double-pulseprocessing...............................65CHAPTER4EXPERIMENTALSETUP...........................734.1Introduction......................................734.2Beamsettings.....................................734.3Particle.................................754.3.1Image2TOFcorrection...........................764.3.2Totalkineticenergy..............................774.4Gecalibration.....................................864.4.1Efycalibration.............................864.4.2Energycalibration..............................94CHAPTER5RESULTS...................................965.1Introduction......................................965.2Long-livedisomericstates..............................965.2.1Introduction..................................965.2.2Identifying115Ru...............................985.2.3Conversionelectronspectroscopy......................985.2.4Interpretation.................................1055.2.5Simulation...................................1105.2.6Concludingremarks..............................1125.3Short-livedisomericstates..............................1125.3.1Double-pulsesinRusetting..........................1125.3.2Double-pulsesinNbsetting.........................1185.4b-delayedgrays....................................1265.4.1Rusetting...................................1265.4.1.1115/118Rh..............................1285.4.1.2116/119Rh..............................1295.4.1.3115/118Pd..............................1325.4.1.4116/119Pd..............................1335.4.1.5114/117Ru..............................1365.4.1.6AllotherPIDgates.........................1365.4.2Nbsetting...................................1385.4.2.1110/113Tc..............................1395.4.2.2111/114Tc..............................1405.4.2.3112/115Tc..............................1415.4.2.4109/112Mo.............................1455.4.2.5AllotherPIDgates.........................145viiCHAPTER6CONCLUSIONSANDOUTLOOK......................1476.1Conclusions......................................1476.2Outlook........................................148BIBLIOGRAPHY........................................151viiiLISTOFTABLESTable2.1b-DecaySelectionRules[1].............................17Table2.2g-rayMultipolarities[1]...............................18Table2.3WeisskopfSingle-ParticleTransitionRates(EginMeV)[1]............19Table3.1Resolutionsofstrips9and2onthebacksideofthedetectorontheshowninthissection.................................38Table3.2ElectrondetectionefyasafunctionofdepthintotheGeDSSDfor3000keVelectrons.Theefywasdeterminedbythenumberofcountswithinthepeakatthefullenergyofthesimulatedelectronsforthestripinwhichelectronoriginated..................................50Table3.3Descriptionofstriparrangementsandpossiblepixelreconstructionintheb-gsummingalgorithm.................................60Table4.1Summaryofthethreebeamsettingusedintheexperiment.............74Table4.2ThepredictedenergydepositionfromLISEwithinthePINsandGeDSSDforthetwoSnbeamsine11003.............................74Table4.3Observedcountsfortransitionsin115Rhand118RhdecayscomparedtotheexpectednumberofcountsiftherewerenoTKEseparation.Theexpectednumberofcountsweredeterminedbyscalingthenumberofcountsofeachgraybythetotalnumberofimplantsforthenumberwithineachgate........85Table4.4Tableofg-rayefencysummingcorrectionsfortheSRMsource.[E]de-notesthetotalefyat"E"keV(calculatedfromsimulation),whilefEgisthepeakefyat"E"keV.Measuredefaredividedbythesummingcorrectiontoaccountforthecorrection..................92Table4.5Thesimulatedcloverg-RayefyatimplantationdepthwithintheGeDSSD.Theefofallindividualcrystalswerecalculated,andthensummedtogetherfortheentirearraytogivetheefyshowninthesecondcolumnofthetable......................................93Table5.1EnergiesofRux-rays.Inthetable,ShellfdenotestheshellbythevalenceelectronandShellidenotestheinitialvalenceshell.ValuesarefromRef.[76].......................................97ixTable5.2Numberofexpectedgraystobedetectedifthepeakat123.8keVwereasingleconversionelectrontransitiongiventhetotalnumberofobservedcountsanddetectorefy................................102Table5.3Multipolaritiesofthetransitionsdiscussedintheanalysisof115Ru.Thecon-versioncoefinthetablehaveanuncertaintyof1.4%[79].........107Table5.4Summaryoftheb-delayedgraysobservedinthiswork..............126Table5.5Summaryofgrayrelativeintensitiesobservedinthiswork............127Table5.6NumberofimplantedionsanddecaysintheRubeamsettingusingacorrela-tiontimeof500ms.................................127Table5.7Tabulatedrelativeintensitiesforthegraysobservedinthedecayof118Rh....128Table5.8Observedcountsfortransitionsin116Rhand119RhdecayscomparedtotheexpectednumberofcountsiftherewerenoTKEseparation.Theexpectednumberofcountsweredeterminedbyscalingthetotalnumberofimplantsforthenumberwithineachgate.............................130Table5.9NumberofimplantsanddecayswiththeNbbeamsetting.............138Table5.10Observedcountsfortransitionsin111Tcand114TcdecayscomparedtotheexpectednumberofcountsiftherewerenoTKEseparation.Theexpectednumberofcountsweredeterminedbyscalingthetotalnumberofimplantsforthenumberwithineachgate.............................144xLISTOFFIGURESFigure1.1Theionizationenergy,ortheenergyrequiredtoremoveanelectronfromagivenelementisshownforelementsuptoZ=92.Noblegasesaremarked,withtheirZgivenbelowtheelementalname.ThedataarefromRef.[23]....4Figure1.2NilssondiagramfornucleiwithA˘110reproducedfromRef.[25]........6Figure1.3Schematicdrawingillustratingtheenergysplittingoftheh11/2orbitalasafunctionofdeformationparameter,b.Thesingleparticleenergyincreasestowardthetopofthe............................6Figure1.4EvolutionofspinsandparitiesintheRuisotopicchain[5,12,29,32Œ34]shownfor(a)positiveparitystatesand(b)negativeparitystates.The(7/2+)statein113Rucouldalsobea(5/2+).Thereisalsoa(7/2-)b-decayingisomeratunknownenergyin113Ru,witha(9/2-)state112.9keVaboveit[34].....8Figure1.5SchematicoftheorderingoforbitalsbetweenN=50andN=82.Theorderingisbaseduponthecalculationsin[25].Positiveparityorbitalsareshownwithasolidline,whilenegativeparityorbitalsaredrawnwithadashedline......9Figure1.6Partiallevelschemesfortheheaviestodd-ARuisotopes.Experimentaldatafrom[4,5,10Œ12,34]................................11Figure1.7TheoreticalPredictionsofthedeformationparameter,bforRuisotopes.Ref-erencesinorderoflegend:[14Œ18,20,21].....................12Figure2.1Inthisgeneralschematicofbdecay,multiplestatesarepopulatedinthedaughternucleus,withthehighestexcitedstateshownhereasanisomericstate,withcompetingb-decayingandinternaltransitionde-exitations.Fig-urelabels:IT,internaltransition;T1=2,half-life;g,gray;b-,bdecay;p,parent;d,daughter;m,metastablestate......................16Figure2.2Cartoonofb-DecaySpectroscopy.Leftsideshowsthearrivalofaheavyioninthedetector,whiletherightsideillustratestheb-decayproducts........22Figure3.1AschematicoftheGeDSSD.Thecrystalishousedinthecylindricalregioninthecenteroftheimage,withtheforthetwosetsofstripstothetopandright.Themechanicalcoolerislocatedwithinthebottomrightcylinderoftheimage,andtheionpumpislocatedtoitsleft.ThisisreproducedfromRef.[6]..............................24Figure3.2Atypicaltracewiththebaselinesubtractedforoneofthebackstrips(bluecurve)andaschematicrepresentationoftheshapeofthetrapezoidaloutput(redcurve)..................................26xiFigure3.3AtypicaltraceshapeforoneofthebackstripsoftheGeDSSD(bluecurve)andthebaselineheight(green)andthetraceheight(red).............27Figure3.4AtypicaltraceshapeforoneofthebackstripsoftheGeDSSD(bluecurve)andshowningreenandredareexamplesoftheregionsofthetraceusedtoobtainameasureoftheenergyofthetrace.....................27Figure3.5The1-Dstripenergycalibrationforthe662-keVtransitionfrom137Csmea-suredimmediatelyafterthecommissioningrun.ErrorbarsindicatetheFWHMofthepeaks................................28Figure3.6Theresolutionsofthehigh-gainstripsintheGeDSSDforthe662-keV137Cstransitionasafunctionofnumberofimplantedionsineachindividualstripforthefewexperiments.Datashownforthefrontsideofthedetector,withtwoedgestripsshownasanexample(strip1and15incircles)andtwomiddlestripsshownasanexample(strips6and9insquare).Theresolutionworsensasthedetectorisbombarded.......................29Figure3.7Theresolutionsofthehigh-gainstripsintheGeDSSDforthe662-keV137Cstransitionasafunctionofnumberofimplantedionsineachindividualstripforthefewexperiments.Datashownforthebacksideofthedetector,withtworepresentativeedgestrips(2and16incircles)andtworepresen-tativemiddlestrips(8and9insquares).Theeffectsoftheimplantationofbeamarelessnoticeableonthebackstrips.....................29Figure3.8Theuncalibratedenergiesoftwoadjacentstripsformultiplicity3eventsfroma137Cssourceonthebacksideofthedetector.Theeffectsofcross-talkappearintheregionsontheedgeofthe..................31Figure3.9(a)Therawenergyhistogramformultiplicity3eventsforfrontstrip5.Gat-ingaroundthepeakat1650ADCunits,correspondingtothefull137Csen-ergydeposition,(b)theeffectsofcrosstalkcanbeenseenintheneighboringstrips,strip6showninblueandstrip4inred...................32Figure3.10Multiplicityofthebackhigh-gainstripsgatedonthe662-keVgrayfrom137Cs.Inredisthemultiplicitybeforecross-talkcorrection,andinblueisthemultiplicityaftercross-talkcorrection.....................33Figure3.11Calibratedstripenergyspectrumforallbackstripsonthedetectorshowingthehigherenergycalibrationpeaks.........................33Figure3.12Dependenceofbackstrip8cross-talkcorrected,energycalibrated137Csspectrumonthecoincidentfrontstrip.Theiszoomedinaroundthe662-keVtransition.................................34xiiFigure3.13Calibratedbackstrip8energyspectrumcomparingthe1-Dcalibration(red)tothe2-Dcalibration(blue)............................35Figure3.14ResolutioninkeVofindividualstripsaftercalibrationthepixelsofthede-tectorwitha137Cssourceafterexperimente11003................36Figure3.15Resolutionofbackstripsfromraw(non-calibratedorcross-talkcorrected)energyspectracomparingenergiescalculatedbythePIXIEtrapezoidal(blackcircles),pulseheightalgorithm(redsquares),andpulseareaalgorithm(bluediamonds)forthe662-keVpeakfroma137Cssource.Thesedataweretakenimmediatelyafterexperimente11503....................37Figure3.16Frontstriplocationvs.backstripenergycalibrationforthere-analyzeddataaftere11503forthe137Cssourceat662-keV.Amuchsmallervaria-tionwithincalibrationasafunctionofstriplocationontheothersideisseencomparedwiththelaterdata............................37Figure3.17Calibrationofthelow-gainstripsutilizingthegainmatchingtotheLISEpredictedenergiestechnique.Showningreen,redandblueareshowntheeventsforstrips8,9,and10,respectively.....................39Figure3.18AnexampletracefromthebackoftheGeDSSD(blue),illustratingthepream-saturation.Themaximumamplitudeis16384,whereasthelow-gainbackstripsreachamaximumwellbeforethemaximumoftheADCrange.Forcomparison,atracefromthefrontoftheGeDSSDisshown(red)......40Figure3.19A2-Dplotofneighboringstripsshowingcross-talkandchargesharing.....41Figure3.20Backstriplocationasafunctionofenergyinfrontstrip4showingthede-pendenceincalibrationonlocationindetector...................42Figure3.21Acomparisonofrecordedenergydepositionfromthe124Sn50+beambe-tweenthe1-Dcalibration(red)tothesubsequent2-Dcalibration(blue)forfrontstrip4.....................................42Figure3.22Thecalibratedenergyforastripinthemiddleofthedetector,strip7.Allmultiplicities(blue)andmultiplicity1aftercross-talkcorrection(red)......43Figure3.23Themultiplicitydistributionasafunctionoftheenergyofstrip7.........44Figure3.24Themultiplicitydistributionsoffrontlow-gaineventsine11003,beforecross-talkcorrection(red)andaftercross-talkcorrection(blue)..........44Figure3.25A2-Ddistributionoftheenergyobservedintwoneighboringstripsinthemiddleofthedetector................................45xiiiFigure3.26Acomparisonoflow-gainstrip7inthe124Snfully-strippedbeambefore(red)andafter(blue)thedurationofthebeamtime.Thefull-energydeposi-tionisnotclearinthedataaftertherestoftheexperiment............45Figure3.27Relativeshift(comparedtotheaveragevalueacrossallstrips)intheenergycalibrationasafunctionofstripnumber,shownforthetwolaterbeamset-tingsine11003...................................46Figure3.28Comparisonofsimulatedandexperimentaleffroma154,155EuSRMsourcelocatedoutsideoftheGeDSSD'scryostat.Theisrepro-ducedfrom[6].Theefyshownisapeakefency.ThetotalnumberofcountsineachpeakintheSRMsourcewasdeterminedforeachstripindi-vidually,andtheresultsfromeachstripweresummedtotheefyplottedinthe................................48Figure3.29graydetectionefyoftheGeDSSD.Simulatedfortwoimplantationdepths.TheisreproducedfromRef.[6].Theefyshownisapeakefy.Thetotalnumberofcountsineachsimulatedenergywasdeterminedforeachstripindividually,andtheresultsfromeachstripweresummedtotheefyplottedinthe................48Figure3.30Efyfordetectinglow-energyelectronsforimplantslocatedat1mm(black)and2mm(red)fromthefrontfaceoftheGeDSSD.Theefywasdeterminedbythenumberofcountswithinthepeakatthefullenergyofthesimulatedelectronsforthestripinwhichelectronoriginated.........50Figure3.31AphotographoftheGeDSSDandSeGAusedforexperimentse11503ande09055viewedfromtheside.Thebeamtravelslefttorightintheimage......................................51Figure3.32AphotographoftheGeDSSDandSeGAusedforexperimentse11503ande09055.Thebeamexiststhepagetowardtheviewer........52Figure3.33Decaycurveof54NiandthewiththeBatemanequations,whichwasusedtodeterminetheelectroncorrelationefy.Thedecayofthe54Niparentisshowninpink,thegrowthanddecayofthe54Codaughterisshowningreen,andthecontributionfromthebackgroundisshowninblue.Theisreproducedfrom[6]...............................53Figure3.34Backstriptimingminusfrontstriptimingvs.frontstripenergy(cross-talkcorrectedand2-Dcalibrated)forimplantevents.Theblackgateshowsthecutplacedonthelow-gainevents.TheeventsshowninthedonotrequireaDEsignalwithinthePINs........................55xivFigure3.35Backstriptimingminusfrontstriptimingfordecayevents.Thetiminggateisinblackonthe..............................56Figure3.36Energyofthestripchosenastheeventlocationvs.thehigh-gaintimingdifferencefor(a)frontstripsand(b)backstrips..................57Figure3.37Partiallevelschemeandfeedingin67Co.DataaretakenfromRef.[66].....59Figure3.38Anillustrationofthestriparrangementsandpixelreconstructionasutilizedbytheb-galgorithmforcaseswithmultiplicity1.(a)Multiplicity1onbothsides.(b)Multiplicity1onasingleside.Onlyonepossibilityexistsforthesecases.........................................61Figure3.39Anillustrationofthestriparrangementsandpixelreconstructionasutilizedbytheb-galgorithmforcaseswhereonesidehasmultiplicity2.(a)Multi-plicity2onbothsides.(b)Multiplicity2onasingleside.Multiplearrange-mentsarepossible.................................62Figure3.40Anillustrationofthestripandenergyarrangementsfortwocaseswheretheenergywithinthestripsissplitbetweenmultiplepixels.(a)IfES2(1)ES1(2)>ES1(2)andES2(1)ES1(2)>ES2(2),thisarrangementputsthemaximumenergyattheintersectionofthestripswiththehighestenergy.(b)Otherwise,ifES2(1)ES1(2)wouldnotresultinthehighestpixelenergy,thisalternatearrangementpreservesthemaximumpixellocation.........63Figure3.41SeGAenergyspectrumshowingthehigherenergygraysat2088.7,2079.8,and2054.2keVusedasgatestoselectthe188.9keVtransitionusedfortestingtheb-gsummingalgorithm.........................63Figure3.42StripenergyspectrumofthebacksideoftheGeDSSDaftergatingonthegraysshowninFig.3.41.Thenumberofcountsinthepeakat189keVisconsistentwiththe10%predictedbysimulation..................64Figure3.43StripenergyspectrumofthefrontsideoftheGeDSSDaftergatingonthegraysshowninFig.3.41.Thenumberofcountsinthepeakat189keVisconsistentwiththe10%predictedbysimulation..................64Figure3.44EnergyspectrumintheGeDSSDfromtheb-gsummingalgorithmtore-createthepixelenergiesgatedonthethreehighenergytransitions,2055,2080,2088in67Fe.Theintensityofthe189-keVtransitionisshown.......65Figure3.45Anexampletraceexhibitingthedouble-pulse-shapesearchedforbythistechnique......................................67xvFigure3.46Thelogofthechi-squaredistributionofthesingle-pulseovertheampli-tudeofthepulseforthefrontstripsofthedetector.Acutoffof3.15(shownasthereddashedline)forthefrontstripswasusedtodeterminewhetherthewasgood.....................................68Figure3.47Thelogofthechi-squaredistributionofthesingle-pulseovertheampli-tudeofthepulseforthebackstripsofthedetector.Acutoffof3.05(shownasthereddashedline)forthebackstripswasusedtodeterminewhetherthewasgood.....................................68Figure3.48Anexampletraceonthebacksideofthedetectorincorrectlylabeledasadoubletraceifthecutoffisloweredto2.9.Theinsetshowsacloserviewoftherisetoillustratethedouble-pulseThetraceisshowninbluewhiletheisshowninred................................69Figure3.49AnexampletraceonthebacksideoftheGeDSSDincorrectlylabeledasasingle-pulsewhenthecutoffwasraisedto3.2.Thistracethatclearlyhastwopartsandshouldbeasadouble-pulse..................69Figure3.50Thelogofthechi-squaredistributionofthedouble-pulseovertheampli-tudeofthepulseforthefrontstripsofthedetectorthatfailedthesingleAcutoffof2.95forthefrontstripswasusedtodeterminewhetherthewasgoodandthereforecouldbeconsideredadouble-pulse..............71Figure3.51Thelogofthechi-squaredistributionofthedouble-pulseovertheampli-tudeofthepulseforthebackstripsofthedetectorthatfailedthesingleAcutoffof2.85forthebackstripswasusedtodeterminewhetherthewasgoodandthereforecouldbeconsideredadouble-pulse..............71Figure3.52Anexampledouble-pulse(blue)withthefunction(red)...........72Figure4.1PIN1energies(DEsignals)fortheRubeamsetting.Thedifferentelementsaremarkedonthe.............................76Figure4.2(a)TOF(arbitraryunits)vs.Image2positionforallparticlesillustratingtheneedtocorrectTOF.(b)ThePIDplotfortheRusettingwithnon-correctedTOF(arbitraryunits).Theisotopesoverlapinthisalthoughtheele-mentsareseparated.................................78Figure4.3(a)ThecorrectedTOF(arbitraryunits)andImage2positionforallparticlesillustratingthesameTOFforallpositionswithintheI2scintillator.(b)ThePIDplotfortheRusettingwiththecorrectedTOF(arbitraryunits)........79xviFigure4.4Cartoondepictingtheproblemcreatedbythecreationofmultiplechargestates.EachchargestateformsaPID.ThesePIDoverlap,creatinggatesthatincludemultiplenuclei.ThechargestatesshownmatchwhatwasobservedintheRusecondarybeamsetting..........................80Figure4.5PIDfortheRusetting.Thespotmarkedcontains115/118Rh,whichwasusedtoinvestigateTKEmeasurementstoseparatedifferentchargestates.......80Figure4.6Cartoondepictingthedepositionofenergyasionsmovethroughtheexper-imentalsetup.Asanexample,theenergydepositioninthePINdetectorsoftheproducedRhisotopesarenoted.........................81Figure4.7TheTKEvs.thepositionoftheionswithintheImage2Scintillatorthatdemonstratetheseparationofchargestates.Thisshowseventsonlyfortheedgestripsinthedetector..........................82Figure4.8TheTKEvs.thepositionoftheionswithintheImage2Scintillatorthatdemonstratethelackofseparationofchargestatesshownonlyforthemiddlestripsinthedetector.................................82Figure4.9b-delayedg-rayspectrumcorrelatedwith115/118Rh.Previously118Rhgrays[72,73]arelabeledinredandpreviously115Rhgrays[74]arelabeledinblack.Thepeakat126keV(115Rh)isthesumoftwoverycloseinenergypeaksat125and127keV(both115Rh),andthecorrelationtimewas500ms............................83Figure4.10b-delayedg-rayspectrumcorrelatedwith115/118Rhandtotheedgestrips.grayspopulatedbythedecayof118Rh[72,73]arelabeledinredandgraysfrom115Rh[74]arelabeledinblack.Thepeakat126keV(115Rh)isthesumoftwoverycloseinenergypeaksat125and127keV(both115Rh),andthecorrelationtimewas500ms........................84Figure4.11b-delayedg-rayspectrumcorrelatedwith118Rhandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof118RhwasappliedtotheSeetextfordetails.........84Figure4.12b-delayedg-rayspectrumcorrelatedwith115Rhandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof115RhwasappliedtotheSeetextfordetails.........85Figure4.13AphotographoftheexperimentalsetupwiththedownstreamsetofcloverspulledbacktoshowtheGeDSSDinfrontoftheupstreamcross.Beamexitsthepagetowardtheviewer.TheninthdetectorisplacedirectlybehindtheGeDSSDatthecenterofthecross.........................87xviiFigure4.14Thecomparisonbetweenexperimentallydetermined(blackcircles)andsim-ulatedef(redsquares)from0-1650keVforasourceplacedonthefrontfaceof(a)clover7and(b)clover9.Theefyforeachcrystalwithinthecloverdetectorwasdeterminedindividually,andthentheefciesfromallfourcrystalsweresummedtogivetheefyinthe..88Figure4.15Thecomparisonbetweenexperimentallymeasured(blackcircles)andsimu-latedef(redsquares)forasourceplacedonthesideofclover9for(a)acrystalclosesttothesourceand(b)acrystalontheoppositesideofthedetectorfromthesource..............................89Figure4.16Thecomparisonbetweenexperimentallydetermined(blackcircles)andsim-ulationedef(redsquares)forasourceplacedonthesideofclover7for(a)acrystalclosesttothesourceand(b)acrystalontheoppositesideofthedetectorfromthesource...........................90Figure4.17(a)Thecomparisonbetweenexperimentallydetermined(blackcircles)andsimulatedef(redsquares)forasourceonthefaceofclover9.Theefshownareforthesumofthedownstreamcloverringusingtheerrorastheuncertainty.(b)Thesameplotas(a),includingthedegreeofmiss-matchbetweensimulationandcloverwithintheuncertainty.Seetextfordetails.Theefyforeachcrystalwithinthedetectorswasde-terminedindividually,andthentheefofallcrystalswereaddedtogethertogivetheefyshowninthe...............91Figure4.18Simulatedefwithinthecloverdetectorsfromtheimplantpositionof1mmdeepintotheGeDSSD.Alsoshownisthetothoseefandtheuncertaintyinthesimulatedef.................94Figure4.19Energyresidualsfor5g-raytransitionsusedforcalibration,asafunctionofdetectornumber.Thedataencompassestheentiretyoftheruntime.......95Figure5.1PIDfor(a)Rusettingand(b)Nbsetting.ThelocationsinthePIDexpectedtocontain115Ruaremarked,alongwiththeirexpectedchargestates.......99Figure5.2b-delayedgrayenergyspectrumforalleventscorrelatedtothedecayof115Ruwithin250msinbothA1900settings.Thestrong292.5-keVtransitionassociatedwiththebdecayof115Ruisclearlyseen................100Figure5.3GeDSSDmaximumstripenergyspectrumfollowingtheimplantationof115Ru(black),foracorrelationof9pixels.Forcomparison,ascaledspectrumoftheb-decayelectrondistribution,takenfromthebdecayof113Tc,issuperimposed(red).................................100xviiiFigure5.4(a)b-delayedg-rayenergyspectrumoccurringaftertheimplantationof115Rubutbeforethe123.8-keVsignalintheGeDSSD.(b)Eventsoccurringafterthe123.8-keVsignalintheGeDSSDupto1safterthe115Ruimplant......101Figure5.5(a)115RudecayeventsobservedintheGeDSSDwithinthesamepixelasthe115Ruionwithin250ms.(b)115RudecayeventsinanadjacentGeDSSDpixeltotheionwithinthesamecorrelationtimeas(a)..............103Figure5.6ThedistancelowenergygraystravelinGetohave5%oftheirinitialinten-sityremaining....................................104Figure5.7TherangeoflowenergyelectronsinGe.Stripwidthis5mmandthecrystalis1cmthick....................................105Figure5.8Decaycurveincoincidencewiththe123.8-keVsignalintheGeDSSDfol-lowingthedecayof115Ru.Theincludesanexponentialparentdecay(green),andaconstantbackground(blue)resultinginahalf-lifeof85(13)ms.Thetotalisshowninred..........................106Figure5.9Thelevelschemefor115Ruassuggestedbythiswork...............106Figure5.10Cloverenergyspectrumincoincidencewiththe˘62-keVpeakinthesinglepixelGeDSSDspectrum(Fig.5.5(a)........................109Figure5.11Theratioofexperimentallyobserved[3,9,80,81](lexp)toWeisskopfesti-mate(lWeiss)forthedecayconstantsofsomeisomericM2transitionsnearA˘115.......................................109Figure5.12Comparisonofthesimulatedstripspectra(red)ofthedecayoftheisomericstatein115Ruandtheexperimentalspectra(blue).................111Figure5.13Comparisonofthesimulatedspectra(red)ofthedecayoftheisomericstatein115Ruandtheexperimentalspectra(blue)forthecoincidentcloverenergydepositions.....................................111Figure5.14Energyspectrumofthesecond-pulseofdouble-pulsesignalsintheRusetting......................................113Figure5.15Energyspectrumoftheofadouble-pulseintheRuset-ting.Thespectrumisconsistentwithenergeticb-decayelectrons.Forrefer-ence,theQ-valueofthedecaydiscussedinthissection,118Pd,is4100(200)keV[82]......................................113Figure5.16Clovergrayenergyspectrumincoincidencewiththe49.3-keVpeakinthesecond-pulseenergyspectrum...........................114xixFigure5.17Partiallevelschemeof118Ag.DataaretakenfromRefs.[83,84].........115Figure5.18GeDSSDsecond-pulseenergyspectrumgatedon(a)118Rhimplantsand(b)118Pdimplantsusingacorrelationtimeof2s...................116Figure5.19Timingdifferencebetweentheandsecond-pulseinadouble-pulsesig-nalgatedonthe49.3-keVpeakinthesecond-pulseenergyspectruminFig.5.14.117Figure5.20Cloverg-rayenergyspectrumincoincidencewithwiththe155.7-keVpeakfromFig.5.14....................................117Figure5.21Timingdifferencebetweentheandsecond-pulsegatedonthe155.7-keVpeak......................................118Figure5.22Energyofthesecond-pulseforisotopesintheNbsetting.............119Figure5.23Energyforthegatedonthe57.1-keVpeakforisotopesintheNbsetting........................................119Figure5.24Coincidentcloverspectrumforthepeakat57.1keVintheGeDSSD.......120Figure5.25Decaycurvegatedonthe57.1-keVpeak.Ahalf-lifeof1.9(2)msisfoundfromthewith280(40)decays..........................121Figure5.26Energyofthesecond-pulsefor(a)109/112Moimplantsand(b)106/109Nbimplants.Bothspectraareshownfora5scorrelationtime............122Figure5.27Timingdifferencebetweenthetwopulsesfor(a)109/112Moimplantsand(b)106/109Nbimplants.................................123Figure5.28Second-pulseenergycorrelatedto107/110Nbimplantswithin1s.........124Figure5.29Timingdifferencebetweentheandsecond-pulseforthepeakat67keVcorrelatedto109/112Moimplantswithin1s....................124Figure5.30Timingdifferencebetweentheandsecond-pulsegatedforthe(a)33-keV(b)95-keV(c)115-keVpeaks...........................125Figure5.31PIDwithsomeofthegroupslabeledwiththechargestatecontam-inants.Labelsinblackarefully-strippedions,bluecorrespondstoH-likeions,andredisforHe-likeions...........................128Figure5.32b-delayedg-rayspectrumcorrelatedto116/119Rhwithin500ms.Previously116Rh[70]graysaremarked......................129xxFigure5.33b-delayedg-rayspectrumcorrelatedwith116/119RhforeventstotheedgestripsoftheGeDSSD.Previouslymeasured116Rhgrays[70]arelabeledwiththeirenergiesinkeV..........................130Figure5.34Image2positionvs.thesumofthePINandGeDSSDenergiesgatesonthe116/119Rhimplants.Ontheleftis116Rhandontherightis119Rh........131Figure5.35b-delayedg-rayspectrumcorrelatedwith116/119Rhandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof116RhwasappliedtotheSeetextfordetails.........131Figure5.36b-delayedg-rayspectrumcorrelatedwith116/119Rhandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof119RhwasappliedtotheSeetextfordetails.........132Figure5.37b-decayg-rayspectrumcorrelatedto115/118Pdwithin500ms.Refs.[83,84]previouslyreported125-keVand379-keVtransitionsinthedecayof118Pd.Ref.[69]reportedat125-keVtransitioninthedecayof115Rh..........133Figure5.38b-delayedg-rayspectrumcorrelatedwith115/118PdforeventstotheedgestripsoftheGeDSSD.Previouslymeasuredgraysaremarked.....134Figure5.39Image2positionvs.thesumofthePINandGeDSSDenergiesgatesonthe115/118Pdimplants.Ontheleftis115Pdandontherightis118Pd.........134Figure5.40b-delayedg-rayspectrumcorrelatedwith115/118Pdandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof115PdwasappliedtotheSeetextfordetails.........135Figure5.41b-delayedg-rayspectrumcorrelatedwith115/118Pdandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof118PdwasappliedtotheSeetextfordetails.........135Figure5.42b-decayg-rayspectrumcorrelatedto116/119Pdwithin500ms.Ref.[83]reportsa91.0keVtransitioninthedecayof116Pd.Afewgraysknownfromthedecayof119Pdareseenhere:256.6,and326.1keVasreportedin[87].Thereisalsowhatmaybeapeakat340keV...............136Figure5.43b-decayg-rayspectrumcorrelatedto114/117Ruwithin500ms.Peaksnear125and179keVlikelyarisefromthedecayof114Ru[88]............137Figure5.44b-delayedg-rayspectrumcorrespondingtothe117/120RhPIDgateillustrat-ingthelackofclearlyvisiblegrays........................137Figure5.45PIDplotfortheNbsettingwiththeisotopegateslabeled.Blacklabeledisotopesarefully-strippedandbluelabeledisotopesareH-like..........139xxiFigure5.46b-decayg-rayspectrumcorrelatedto110/113Tcwithin500ms.The98.5-keVand164.3-keVgrayspopulatedinthedecayof113Tcarereadilyappar-ent[4].Additionally,the263.2-keVtransitioninthedaughterdecayisalsovisible[90].....................................140Figure5.47b-decayg-rayspectrumcorrelatedto111/114Tcwithin250ms.Severalofthe114Tcgraysareapparent.AsreportedinRef.[71],thegrayenergiesareat265.1,298.0,443.0,563.4keV..........................141Figure5.48b-delayedg-rayspectrumcorrelatedwith111/114TcforeventstotheedgestripsoftheGeDSSD.PreviouslymeasuredgraysarelabeledbyenergyinkeV....................................142Figure5.49Image2positionvs.thesumofthePINandGeDSSDenergiesgatesonthe111/114Tcimplants.Ontheleftis111Tcandontherightis114Tc.........142Figure5.50b-delayedg-rayspectrumcorrelatedwith111/114Tcandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof111TcwasappliedtotheSeetextfordetails........143Figure5.51b-delayedg-rayspectrumcorrelatedwith111/114Tcandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof114TcwasappliedtotheSeetextfordetails.........143Figure5.52b-decayg-rayspectrumcorrelatedto112/115Tcwithin500ms.The236.8-keV,andpossiblyasmallamountofthe511.5-keVtransitioninthedecayof112Tcisvisible[89].................................144Figure5.53b-decayg-rayspectrumcorrelatedto109/112Mowithin500ms.The236.8-keVtransitioninthedecayofthedaughter112Tcisvisible[89].........145Figure5.54b-decayg-rayspectrumcorrelatedto108/111Mowithin500ms.Nob-delayedgraysareapparent.............................146xxiiCHAPTER1INTRODUCTION1.1NuclearstructureandisomerspectroscopyThestudyofnuclearstructureseekstodescribethemostfundamentalpropertiesofnuclei.Inaquantummechanicalpicture,protons(Z)andneutrons(N)particularenergylevels;therelativeenergiesoftheseorbitalsvaryacrossthenuclearchart.Ofparticularinterestisobservinghowanenergylevelofagivenspinandparityshiftsinenergyasmoreprotonsorneutronsareaddedtothenucleus.Theprogressionofenergylevelswithspinsandparitiescaninformtheunderstandingofhowthestructureofthenucleusevolves,hownucleonsnuclearshells,andhownuclearorbitalsshiftasthenucleuschangeswithchangesinneutronandprotonnumbers.Excitedstateswithametastable,orlong-lived,half-lifearereferredtoasisomericstates(de-notedasAmZN).Thehalf-livesofisomericstatesspreadawiderange,nanoseconds[1]tomanythousandsofyears[2].Anexcitedstate'stransitioncanbecomedelayed,andthusisomeric,ifthetwostateshaveverydifferentspinsordifferentunderlyingnuclearstructure[1,2].There-fore,thediscoveryandofisomersisimportantforthestudyofnuclearstructure.Inparticular,thestudyofisomericstatesisimportantforinvestigatingthespinsandparitiesofnuclearstatesbecausethepropertiesofisomerictransitions,suchasthetransition'smultipolarity,canplaceconstraintsontheofthatstate.Isomericstatescandecayinavarietyofdifferentways.Someisomersdecayviabdecay[3,4],whileothersundergointernaltransitions[3,5].Internaltransitionsmayresultintheemissionofgraysandconversionelectrons.Therelativeintensitiesbetweentheconversionelectronsandgraysplaceconstraintsonthechangeinspinsandparitiesbetweentheinitialandstates.Therefore,spectroscopyofgraysandconversionelectronsisapowerfultoolforexploringnuclearstructure.11.1.1b-decayspectroscopyOneexperimentalprobethatcanbeusedtostudyisomericstatesisb-decayspectroscopy.bdecaycanpopulatemultipleexcitedstatesinthedaughternucleus,andg-raydecayfromthosestatescanpopulateadditionalstates.Arecentb-decayexperimentattheNationalSuperconductingCyclotronLaboratory(NSCL)ispresentedinthisworkandfocusesontheneutronrichA˘110regionofthenuclearchart.1.1.2TechniqueintroductionRecently,aGeDouble-SidedStripDetector(GeDSSD)[6]wascommissioned.WhiletraditionalDSSD'saremadeofSi,theuseofGehasanumberofadvantages,whicharisefromthegreateravailablethicknessesandhigherZofGeincomparisontoSi.TheGeDSSDoffersanincreasedb-decaydetectionefy,andalsooffersahighefyforthedetectionoflow-energygraysandconversionelectrons,makingthisdetectoridealfortheobservationofisomericstates.Lowerenergytransitionsareexpectedtohavealongerhalf-life,basedupontheWeisskopfestimateoftheirdecayconstant(SeeSection2.3.1).Therefore,thestudyoflowenergygraysisimportant.1.2Applicationofb-decayandisomerspectroscopytoA˘110nucleiOneregionofthenuclearchartthathaslongbeenthoughttoexhibitsignaturesofchangingnuclearshape[7]isthemassnumberA˘110neutronrichZr,Nb,Mo,Ru,Rh,andPdnuclei.Whilethereareseveralinterestingaspectsofthesenuclei,thesearchforisomericstatescanaddresstheeffectsofthenh11=2orbitalonthestructureintheregion.WithneutronnumbersrangingbetweentheN=50andN=82shellclosures,manypositiveparityorbitalsareavailable,withthepossibilityofexcited,high-spin,negativeparitystatesarisingfromtheh11=2orbital.Severaloftheisotopesinthisregionhavenegativeparityisomericstates[3Œ5,8Œ13],withhalf-livesvaryingfrom14ns[10]upto5.5h[8].21.2.1ShellmodelintroductionExperimentaleffortshavebeencarriedoutintomoreandmoreneutronrichnuclei,andmanyre-searchgroupshaveputforththeoreticaleffortstoexplaintheobservedphenomena(forexample:theprevalenceofisomericstates,signaturesoflargeprolatedeformations),andtopredictwhetheradditionalchangesintheshapesofthenucleiareexpectedathigherneutronnumbers[14Œ22].However,theexperimentaloftheregionisfarfromcomplete,andtheoreticalpre-dictionsvaryforthenucleardeformations,aswellasthelocationalongisotopicchainswherethechangesinnuclearshapeareexpected.TheobservedshapeevolutionoftheA˘110nucleiarisefromchangesintheunderlyingnuclearstructure.Intheshellmodeldescriptionofthenucleus[1],protonsandneutronsarearrangedinaseriesofshells,andthespacingandoftheseshellsdeterminethepropertiesofaisotope.Thisisanalogoustothebehaviorexhibitedbyelectronsinatomicsystems,wheretheperiodictrendsoftheelementsanunderlyingshellstructure.Whenanentireshellisasisthecaseforthenoblegases,theamountofenergytoremoveasingleelectronincreases,andthesystemexhibitsanincreasedstability.TheionizationenergyforatomicelectronsisshowninFig.1.1.Innuclei,similarpeaksareseenintheneutronandprotonseparationenergies,ortheenergyrequiredtoremoveaneutronfromthenucleus.Thenumbersofprotonsandneutronsresultinginrelativelymorestablenucleithantheneighboringnucleiarereferredtoasmagicnumbers.Thenumberofnucleonsthatformclosedshellsforneutronsandprotonsaredifferentfromthoseoftheelectronshellsduetoadifferentunderlyinginteractionpotential.Knownmagicnumbersforbothneutronsandprotonsare2,8,20,28,50,82,andforneutrons,anadditionalmagicnumberof126isknown.Thesphericalshellmodel[24]describesthenucleusasasetofenergylevelsexistingasorbitalswithinanuclearpotential.Asmoreprotonsandneutronsareaddedtoanucleus,higherenergyorbitalsbecomeTheevolutionofnuclearstructurecanalsobestudiedfromthestandpointofcollectiveexci-3Figure1.1Theionizationenergy,ortheenergyrequiredtoremoveanelectronfromagivenelementisshownforelementsuptoZ=92.Noblegasesaremarked,withtheirZgivenbelowtheelementalname.ThedataarefromRef.[23].tations,orexcitationsinvolvingmultiplenucleons.Oneoftheeffectsofsometypesofcollectiveexcitationisachangeintheshapeofthenucleus,whichcanbeobserved,forexample,inrotationalmotionofthatnucleus.Thedeformationofthenucleuscanbedescribedbyitselectricquadrupolemomentforaxiallysymmetricdeformations,withasphericalnucleushavingamomentof0e-barns,aprolate(football-like)nucleushavingapositivemoment,andanoblatenucleus(discus-like)havinganegativequadrupolemoment.Prolateandoblatedeformationsareellipsoidalshapeswheretwooftheaxesoftheellipsoidarethesameinlength,withthethirdaxiselongatedorcompressed.Thequadruoplemomentmaybeexpressedasfollows[1]:Q=25Ze(b2a2)(1.1)whereQisthequadrupolemoment,Zistheprotonnumber,eisthechargeoftheelectronandaandbarethesemi-minorandsemi-majoraxesoftheellipse.Thedeformationofthenucleuscanbeparameterized[1]baseduponthelengthoftheaxesoftheellipse:b=43rp5baRavg(1.2)4whereaandbarethesemi-minorandsemi-majoraxes,respectively,RavgistheaverageradiusR2avg=12(a2+b2),andbisreferredtoasthedeformationparameter.Forsphericalnuclei,bis0,whileprolateandoblatenucleihaveapositiveandnegativeb,respectively.TheNilssonmodeldescribestheevolutionofthesphericalshellmodelorbitalswhenplacedintoadeformednuclearpotential[1].Thesplittingofthenuclearorbitals,removingorbitalde-generacy,asafunctionofthedeformationparameter,b,isoneofthemodelpredictions.Forexample,aNilssondiagramforA˘110nucleiwascalculatedinRef.[25](Fig.1.2).Theenergylevelsaresplitaccordingtotheprojectionofthesingle-particleangularmomentumontothenu-clearsymmetryaxis,andarerepresentedbythequantumnumberW.Asphericalorbitalwillsplitinto(2j+1)=2levels,wherejisthetotalorbitalangularmomentum,withthehighestangularmo-mentumstateshighestinenergyforprolatedeformationsandthelowestangularmomentumstateshighestinenergyforoblatedeformations(Fig.1.3).Therefore,theground-statespinsandparitiesofodd-AnucleicanhelpwithidentifyingthedegreeofdeformationasafunctionofAwithinanisotopicchain.Higher-lyingorbitalswithinthecalculationwithdifferentspinsandoppositeparitiesareassociatedwiththepresenceoflow-lyingisomericstates.1.2.2RuisotopesSeveralisotopicchainsintheA˘110regionshowevidenceofchangingnuclearshapeandtheorylikewisepredictsachangeinnuclearshapeasAincreasesalongtheseisotopicchains.Examplesofchangingnuclearshapeincludereducedenergiesintheexcited2+statesineven-evennuclei[26Œ28](sphericalnucleihavehighexcited2+energiesduetogapsbetweenclosedshells),highspindatainodd-Anuclei[28,29](band-crossingmayberelatedtoshapetransitions),andreducedquadrupoletransitionstrengths[30](thequadrupolemomentisrelatedtothedeformationparameterbyEq.1.1).Individualtheoriespredictchangesatdifferentmassnumbers.Isomericstatesinodd-Anucleicanbeusedtosearchforofdeformationbyconstrainingthespinandparityofnuclearstates.Becauseisomerscanariseduetolargechangesinspinorachangeinparity,inadditiontolowerenergytransitionsdelayingthetransitionrate,betweentwo5Figure1.2NilssondiagramfornucleiwithA˘110reproducedfromRef.[25].Figure1.3Schematicdrawingillustratingtheenergysplittingoftheh11/2orbitalasafunctionofdeformationparameter,b.Thesingleparticleenergyincreasestowardthetopofthe6levels,thecharacterofthetransitionindicatesthemagnitudeofthechange(SeeSection2.3.1formoredetails).FortheRuisotopeswithNbetween50and82,thereisonlyasingleorbital,theh11=2orbital,withanegativeparity.Thusifthemultipolarityofanisomerictransitionindicatesthatthereisachangeinparity,oneofthetwostatesmostlikelyarisesfromthisorbital.Forexample,in115Ru,anM2isomerictransitionindicatingachangeinparitywasfound[5].Theground-statespinandparity,whichwasfoundtotentativelybe(3/2+)[12],isdiftoplaceinaprolateorspherical(Fig1.2)withN=71,andthereforecouldsignalashifttomoreoblateshapes.Thissectionwilloutlinetheconsiderationsthatledtothepresentstudy,usingtheRuisotopicchainasanexampletoillustratethekindofstructuralevolutionpresentintheA˘110regionofthenuclearchart.1.2.2.1PreviousexperimentalresultsIntheRuisotopicchain,theheaviestnucleuswithpreviouslymeasuredexcitedstatesis117Ru[31].Anisomericstateat185keVwithahalf-lifeof2.487+0:0580:055mswithanunknownspinandparitywasobservedandnospinorparitywasassignedfortheground-state[31].Fig.1.4illustratesthesystematicsforseveralodd-ARuisotopesasafunctionofA.Forthesenuclei,63N71,availableneutronorbitals(Fig.1.2)includetheevenparity2d5=2,1g7=2,3s1=2,2d3=2andtheoddparity1h1=2orbitals.TheexpectedorderingoftheorbitalsbetweenN=50andN=82isillustratedinFig.1.5.Thus,negativeparitystates,someofwhichmaybeisomeric,canarisefromanunpairedneutronintheh11=2orbital,whilepositiveparitystatescouldpotentiallyarisefromtheunpairedneutronoccupyinganyoneoftheotherorbitals.ForlessmassiveRuisotopes,theevolutionofthespinsandparitiesoftheenergylevelscanprovidesomeinsightintothechangingnuclearstructure.Inthelessmassiveodd-Anuclei,thespinsandparitiesoftheground-statescanbecomparedtotheexpectedspinsandparitiesonaNilsondiagramsuchastheoneshowninFig.1.2inordertogainsomeinsightastowhetherthesenucleiareprolateoroblatedeformed.Thesenucleishowtheprogressionofspinsandparitiesleadinguptothenucleidiscussedinthiswork,andare7Figure1.4EvolutionofspinsandparitiesintheRuisotopicchain[5,12,29,32Œ34]shownfor(a)positiveparitystatesand(b)negativeparitystates.The(7/2+)statein113Rucouldalsobea(5/2+).Thereisalsoa(7/2-)b-decayingisomeratunknownenergyin113Ru,witha(9/2-)state112.9keVaboveit[34].8Figure1.5SchematicoftheorderingoforbitalsbetweenN=50andN=82.Theorderingisbaseduponthecalculationsin[25].Positiveparityorbitalsareshownwithasolidline,whilenegativeparityorbitalsaredrawnwithadashedline.representativeofthenucleiwithintheA˘110regionofthechartofthenuclides.ResultsfromB(E2)measurementsindicatedadeformationparameter,bintheevenAisotopesbetween102Ruand108Rutoincreasefrom0.20to0.25[35].Otherworkmeasuringlifetimesin108,110Rufoundabof0.29(1)[36].Therefore,thespinsandparitiesoftheodd-AisotopesmaybecomparedtotheNilssondiagramatbbetweenapproximately0.2and0.3forisotopeswithAlessthan110.In107Ru(N=63),theground-statespinandparityis(5/2+)[32].Thisspinandparitycanbeobtainediftheoddneutronin107Ruoccupiesthed5=2singleparticlestateintheW=5/2projectionatadeformationofb˘0.3.AddingtwoneutronstoN=65,theground-statespinandparityof109Ruis(5/2+)[29],whichgivenadeformationparameterof˘0.15wouldpopulatetheW=5/2projectionoftheg7=2orbital.Withtwoadditionalneutrons(N=67),111Rualsohasaground-statespinandparityof(5/2+)[33],placinganeutronintheg7=2orbitalatslightlyhigherprolate9deformations.Thereis,however,somehigh-spindatathatsuggestsatransitiontooblateexcitedstatesatA=111[28,29].Aspinandparityof(1/2+)[34]fortheN=69113Ruisotopecouldsignalashifttooblateshapes,asthepredictionaccordingtothediagraminFig.1.2suggestsaspinandparityof(5/2)forab˘0.2inanh11=2orbital.Onewaytoexplainthisthisobservationwouldbethepopulationofthes1=2orbitalatb˘-0.15.Alternately,placinganeutronintothed3=2orbitalatveryslightoblatedeformationscouldalsoyieldaspinandparityof(1/2+)atN=69.Finally,addingtwomoreneutrons,reaching115Ru(N=71)thespinandparityoftheground-stateisexpectedtobe(3/2+)baseduponbfeedingsandsystematics[12].Oblatestatesfromthed3=2orbitalatab˘-0.15couldexplainthespinandparity.WhilelighterisotopesgiveexperimentalsuggestionsofprolatecertainlymoreworkintheheaviestRuisotopesisneededtoclarifytheinterpretation.Byusingexperimentalevidencetodeducetheground-statespinsandparitiesinthemoremassivenuclei,thevariationofdeformationwithintheA˘110nucleicanbeItisimportanttonotethatthespinsandparitiesofmanyofthelevelsinthesenucleiareuncertain,soupthespinandparityassignmentwouldclarifytheinterpretationfurther,asincorrectspinandparityassignmentscouldchangetheinterpretationoftheresults.Experimentalresultsfortheheaviestodd-ARuisotopeshavefoundisomericstateswithspinsandparitiesof(7/2-)and(9/2-),whichwouldmostlikelyoriginatefromtheneutronh11=2orbital[4,5,10Œ12,34],atanoblatedeformationofb˘-0.15.Severaloftheseisomericstateshaveaknownhalf-lifebutunkownenergy.PartiallevelschemesfortheisotopeswithisomericstatesareshowninFig.1.6.ItisthereforeimportanttoplacetheseisomericstateatexactenergiesandtosearchformoreisomericstatesinheavierRuisotopes,andtheneighboringisotopicchains.Theenergyofagivenisomericstateisrelatedtoitshalf-life:thelowertheenergy,thelongerthehalf-life[1](SeeSection2.3.1formoredetailsabouttherelationbetweentransitionenergyanddecayconstant).Withtheenergyofatransitionknown,anestimateforthedecayconstantcalledtheWeisskopfestimatemaybecalculated.Thisvariesdependinguponthecharacterofthetranstion,whichinturnisindicitiveofthechangeinspinandparitybetweenthetwostates.10IntheA˘110regionofthenuclearchart,forunpairedneutrons,achangeinparityindicatesthattheh11=2orbitalispopulatedbyoneofthetwostates.Onceconversionelectronspectroscopyfollowingtheisomericdecayscanbeusedtodeterminetransitionmultipolaritiesandtocheckthetentativespinandparityassignments.Statesinhigh-massnucleiwithlowtransitionenergiesandhighmultipolaritieswilllikelyhavestrongconversionelectronemission.Theemittedconversionelectronscaneasilybemissedinmanydetectionsystems.TheGeDSSDmaybeusedtostudythesenucleitosearchfortheunobservedlow-energyelectrons.Figure1.6Partiallevelschemesfortheheaviestodd-ARuisotopes.Experimentaldatafrom[4,5,10Œ12,34].1.2.2.2TheoreticalpredictionsTherehasbeenmuchtheoreticalworkfocusedondescribingtheobserveddeformationsintheA˘110region.Whilemanyofthecalculationspredictchangesinnuclearshapealongtheisotopic11chainsinthisregion,thecalculationsdifferastotheexactlocationoftheshapechanges.SometheoreticalpredictionsforRuisotopesareshowninFig.1.7.Figure1.7TheoreticalPredictionsofthedeformationparameter,bforRuisotopes.Referencesinorderoflegend:[14Œ18,20,21].InRuisotopes,atransitionbetweennuclearground-stateshapesfromprolatetooblateispre-dictedanywherefromA=104[20]toA=110[14,17],remainingprolateinonecalculationuptoA=114[16].Athigherneutronnumbers,thecalculationseventuallyreturntomoresphericalshapes.1.3DissertationoutlineThisworkdescribesthecharacterizationanduseofaGeDSSDtoobserveandidentifyisomericstatesinexoticnuclei.b,g,andelectronspectroscopywillbedetailedinChapter2.TheGeDSSDwillbedescribedinmoredetailinChapter3,focusingontwoexperimentsusedtocharacterizethedetector.TherestofthedocumentwilldetailtheresultsoftheapplicationoftheGeDSSDtothestudyofthenuclearstructureofA˘110nuclei.Chapter4willdetailthesetupoftheNSCLexperiment,12includinganalyticaltechniquesanddataacquisitiontechniquesnotdiscussedpreviously,aswellasionTheresultsoftheexperimentwillbedetailedinChapter5,splitintothreesections:long-livedisomers(focusedon115Ru),short-livedisomersandb-delayedgrays.Finally,Chapter6willsummarizeandconcludethepresentation.13CHAPTER2TECHNIQUE2.1IntroductionThischapterincludesadiscussionoftheexperimentaltechniquesusedwithinthiswork.First,theprinciplesofb-decayspectroscopywillbepresented.Then,othertransitionsandradiationtypesthatmaybepresentinbdecayandthedetectorsystemsutilizedinthisstudywillbepresented,2.2b-decayspectroscopy2.2.1bdecaybdecayisaselectivespectroscopictoolthatisusedextensivelytostudynuclearstructure.b-decayspectroscopycanbeusedtomeasureavarietyofnuclearstructureobservables,includinghalf-lives,branchingratios,andexcitedstateenergies.Thisinformationcanbecombinedtoofferconstraintsonthespinsandparitiesofstates.Inbdecay,aparentnucleusdecaystoitsdaughter,convertingaprotonintoaneutron(orvice-versa),keepingthetotalnumberofnucleonsconstant.Therearethreemodesofbdecay:b:AZN!A(Z+1)+(N-1)+b+¯ne+Qb(2.1)b+:AZN!A(Z1)-(N+1)+b++ne+Qb(2.2)EC:AZN+e!A(Z1)(N+1)+ne+Qb(2.3)wherebisabetaparticle(positronorelectron),eisanatomicelectron,neisanelectronneutrino,¯neisanelectronanti-neutrino,andQbistheb-decayQ-valueofthereaction.bdecayoccursthroughaseriesofisobars(nucleiwiththesameA)endingatastablenucleus.14Thehalf-livesofb-decayingnucleivarygreatlyacrossthechartofthenuclides,rangingfrommillisecondsinthemostexoticnucleitothousandsorevenbillionsofyearsinnucleiclosertostability.Assumingthataradioactivesamplestartswithnodaughternucleipresent,thenumberofionsofanygenerationatanytime,t,canbeexpressedusingtheBatemanequationsasfollows[1]:Nn=C1el1t+C2el2t+C3el3t+:::+Cnelnt(2.4)whereNnisthenumberofnucleiofthenthgenerationattimet,listhedecayconstant,tistime,andtheCncoefare[1]:Cn=l1l2::::ln1(l1ln)(l2ln):::(ln1ln)N01(2.5)whereN01isthenumberofparentnucleiattimet=0.TheBatemanequationsmaybeusedtoextractthenumberofnucleiandthedecayconstantofaparentnucleusfromthevariationoftheactivitywithtime.Adecaycurveplottingthetimedifferencebetweenthedetectionofthearrivaloftheparentnucleustotheexperimentalstation(assumingthetimebetweentheproductionoftheionandit'stransporttotheexperimentalstationisnegligibleonthetimescaleofthedecay)andthedetectedelectronemissionfromthenucleusmaybewithcontributionsfromthedecayingparent,thegrowthanddecayofthedaughters,andtypically,constantbackgroundevents,yieldingthedecayconstantoftheparentl1.Thehalf-lifeissimplydeterminedviatherelation:T1=2=ln(2)l(2.6)Thetotalnumberofnucleimaybefoundbyintegratingthenumberofcountsundertheexponentialcurveoftheparentdecay,ifallparentnucleidecayandtakingintoaccountthedetector'sefy.bdecaycanpopulatemultiplestatesinthedaughternucleus,whichsubsequentlyfurtherdecaytowardtheground-state.Ageneralschematicofb-decayisdisplayedinFig.2.1.graysorconversionelectronsemittedfollowingbdecayarereferredtoas"b-delayed"particles.15Figure2.1Inthisgeneralschematicofbdecay,multiplestatesarepopulatedinthedaughternucleus,withthehighestexcitedstateshownhereasanisomericstate,withcompetingb-decayingandinternaltransitionde-exitations.Figurelabels:IT,internaltransition;T1=2,half-life;g,gray;b-,bdecay;p,parent;d,daughter;m,metastablestate.2.2.2b-decayselectionrulesTheselectionrulesforcaseswherethereisnonetorbitalangularmomentumcarriedbytheelectronandantineutrinoareachangeinnuclearspin,DJ,of0or1,andnochangeinparity,Dp=0.Suchadecayisreferredtoasan"alloweddecay".Decayswithachangeinnetangularmomentumorachangeinparityarereferredtoas"forbiddendecays".Despitewhatthenameimplies,forbiddendecaysdooccur,albeitatalowerratecomparedtoallowedtransitions.TheselectionrulesforbdecayaresummarizedinTable2.1.Onemethodtodistinguishbetweenallowedandforbiddendecaysisthroughtheirftvaluecalledthecomparativehalf-life.Thetreferstothepartialhalf-lifeofthebdecaytotheparticularstateofinterest,whichmaybecalculatedfromthebranchingratio,BRi:li=lBRi(2.7)T1=2i=ln(2)li(2.8)16Table2.1b-DecaySelectionRules[1].TransitionTypeDpDJlogftSuperallowedNo02.9-3.7AllowedNo0,14.4-6.0FirstForbiddenYes0,1,26-10SecondForbiddenNo1,2,310-13ThirdForbiddenYes2,3,4>15wherelisthetotaldecayconstant,liisthepartialdecayconstanttoagivenstateandT1=2iisthepartialhalf-lifeforthedecaytothestate.Thepartialhalf-lifeismultipliedbytheFermiintegral,ftotheftvalueforthedecay[37].ValuesfortheFermiintegralthatrepresentthephase-spaceavailabletothedecayareavailableintabulatedform,forexampleinRef.[38].Ashalf-livescanvarybymanyordersofmagnitude,ftvaluesareoftenreportedaslogft[1].ThelogftrangesforthevarioustypesofbdecayareindicatedinthelastcolumnofTable2.1.2.3Electromagnetictransitions2.3.1gdecayThemultipolarityofanemittedgrayvariesdependinguponthechangeinparityandspinsoftheandinitialstates,asdescribedby:jJiJfjl(Ji+Jf)(2.9)whereJisthenuclearspinoftheinitial(i)andlevels(f)andlistheamountofangularmomentumcarriedawaybythegray.Itisforbiddenforasinglephotontocarryaway0¯hunitsofangularmomentum;a0+to0+transitionmustoccurviainternalconversionorinternalpairproduction(possibleonlywhentheenergyofthetransitionexceeds1.022MeV).Ag-raytransitionisbyitsmultipolarity(Table2.2)andalsowhetheritisanelectricormagnetictransition,thelatterdictatedbythechangeinparityofthenuclearstates.17Table2.2g-rayMultipolarities[1].MultipolaritylDpE11YesM11NoE22NoM22YesE33YesM33NoE44NoM44YesTheg-raytransitionratedependsonitscharacterandmultipolarity.Onecommonlyusedesti-mationoftransitionrate(l)istheWeisskopfSingle-Particleestimate[1].Thisestimateassumesthatagiventransitionistheresultofasinglenucleonmovingbetweentwostates.Theequationsfortransitionratesofthe5multipolaritiesofbothelectricandmagnetictransitionsaregiveninTable2.3.Notethatelectrictransitionsofthesamemultipolearefasterthanthecorrespondingmagnetictransition,andhighermultipoletransitionsareslowerthanlowermultipolesofthesametype.ExperimentallifetimesfortransitionratescanbehinderedorenhancedbyafewordersofmagnitudeincomparisiontoWeisskopfestimates[37]bynucleareffects.Typically,E2valuesareenhancedovertheirWeisskopfestimates[1],whileE1transitionsaremorehindered[37].Weis-skopfestimatescanbeusefulfortheanalysisofisomericstateswheretherearemultiplepossiblede-exitationspossible.Theestimatescanalsobeusefulinassigningmultipolaritiestotran-sitions,whereWeisskopfestimatesarecomparedtoexperimentaltransitionsrates,andthedegreeofagreementindicatestheaccuracyoftheassumptionofasingleparticletransition.2.3.2InternalConversionAprocessthatcompeteswithg-rayemissionisinternalconversion-electronemission.Internalconversionoccurswhenanucleusinanexcitedstateinteractswithanatomicelectronandtheelectronissubsequentlyemittedfromthenucleus.Thevacancyisbyoutershellelectrons,18Table2.3WeisskopfSingle-ParticleTransitionRates(EginMeV)[1].Multipole(l)E(ls-1)M(ls-1)11.031014A2/3Eg33.151013Eg327.28107A4/3Eg52.24107A2/3Eg533.39101A2Eg71.04101A4/3Eg741.0710-5A8/3Eg93.2710-6A2Eg952.4010-12A10/3Eg117.3610-13A8/3Eg11emittingX-raysorAugerelectrons.TheemissionofAugerelectronsoccurswhentheenergyfromavacancyintheelectronshellsistransferredtoanotherelectron,whichisthenemitted.TheyielddescribestheratioofX-rayemissiontoAugerelectronemission[39].Theenergeticsofinternalconversionisgovernedbythefollowingequation:EIC=ETEBE(2.10)whereEICistheenergyoftheconversionelectron,ETistheenergyofthetransition,andEBEisthebindingenergyoftheatomicelectron.Foragiventransition,theinternalconversioncoefagivestherelativeintensityofg-rayandinternalconversiontransitions[1]:a=numberofconversionenumberofgrays=lIClg(2.11)wherelICisthetransitionrateofconversionelectronsandlgisthetransitionrateofgrays.Thetotalinternalconversioncoefatotisthesumofconversioncoefoverallatomicsubshells[1]:atot=aK+aL+aM+:::(2.12)whereK,L,andMrepresenttheatomicsubshells.Theconversioncoefforshellsclosertothenucleuswilltendtobehigherthanthatforshellsfartherfromthenucleus,giventhegreatereaseofinteractionwiththenucleusduetoproximity.19Internalconversioncoefcanbeutilizedtoinferthemultipolarityofatransition.Ap-proximateformulasforinternalconversioncoefare[1]:a(El)=Z3n3ll+1 e24pe0¯hc!4 2mec2E!l+5=2(2.13)a(Ml)=Z3n3 e24pe0¯hc!4 2mec2E!l+3=2(2.14)wherelisthemultipoleorder,nistheprinciplequantumnumberoftheejectedelectron,ande24pe0¯hcisthestructureconstant,whichis˘1/137.Fromtheserelations,onecanseethatinternalconversionbecomesmoreimportantatheaviermasses,andlower-energytransitions.Inequations2.13and2.14,oneassumesthatonlythelowestlcontributes,thatthebindingenergyintheKshellislessthanthetransitionenergy,andthatrelativisticeffectsmaybeignored[40].TherearetwocomplimentarymethodstodetermineconversioncoefdetectingtheX-raysordetectingtheemittedconversionelectronsthemselves.Measuringtheconversionelectionsdirectlyispreferred.Alternately,thenumberofdetectedk-shellX-rays(correctedfordetectorefy)canbetakenasameasureofthenumberofconversions.However,iftherearemultipleconvertingstateswithinanucleus,andnocoincidenttransitionstogateupon,thismethodwillnotbeableuniquelydeterminetheconversioncoef2.4b-decayspectroscopyexperimentaldesignAnoverviewofb-decayspectroscopyatfragmentationfacilitiessuchastheNSCLispresentedinthissection.DatawillbepresentedfromthreedifferentexperimentscarriedoutattheNSCL,e11503,e09055,ande11003,whichwerefocusedon67Fe,54Ni,andA˘110nuclei,respectively.ThetwoexperimentswereusedtocharacterizeaspectsoftheGeDSSD'sperformanceforthedetectionofelectronswhilethelastwasthestudyofisomericstatesnearA=110.Thefeaturesincommontoalloftheexperimentswillbeprovidedhereandmoredetailwillbegiveninlaterchapters.20AllisotopeswereproducedattheNSCLinfragmentationreactionsattheCoupledCyclotronFacility(CCF).TheA1900fragmentseparator[41]selectedtheionsofinterestoutofthosepro-ducedinthetarget.TheseparatedionsthenpassedthroughthinPINdiodedetectors,whichwereutilizedforenergyloss(DE)andtimeof(TOF)measurements.Energylossandtimeofmeasurementsallowedisotopiconanevent-by-eventbasis.Ionswerethendeliveredtotheexperimentalstationanddepositedinaposition-sensitivesemiconductordetector.InsteadofusingaSiDouble-SidedStripDetector(DSSD)forthispurpose[42Œ49],theionswereimplantedintoaGeDSSD[6]inthepresentseriesofexperiments.TheGeDSSDwassurroundedbyarraysofotherdetectorstoobserveb-delayedgraysescapingthecentraldetector.ArraysthathavebeenutilizedinconjunctionwiththeGeDSSDincludetheSegmentedGermaniumArray(SeGA)[50]andtheYaleCloverarray[51].Theimplantedheavyionswerecorrelatedwithsubsequentdecaysusingbothpositionandtimeinformation(Fig.2.2).Validdecayeventsandheavy-ionimplantationeventsmustoccurphysicallyclosetogetherinthedetector,andinatimewindowthatissetbasedupontheimplantationrateandthehalf-livesofthenuclei.Positiondeterminationwasaccomplishedbyeithertakingthestripwiththegreatestamountofdepositedenergyfortheeventorbycalculatingtheenergyweightedaveragestriplocation.Thetiminginformationinthethreeexperimentswasprovidedbyadigitaldataacquisitionsystem.21Figure2.2Cartoonofb-DecaySpectroscopy.Leftsideshowsthearrivalofaheavyioninthedetector,whiletherightsideillustratestheb-decayproducts.22CHAPTER3GERMANIUMDOUBLE-SIDEDSTRIPDETECTOR3.1IntroductionInthischaptertheGeDSSDwillbediscussedindetail.Section3.2givesthetechnicaldetailsofthedevice.TheenergycalibrationoftheGeDSSDwillbedescribedinSection3.3.Section3.4containstheelectronandg-rayefyofthedevice.SomegeneralexperimentaltechniqueswillbedescribedinSection3.5.Thechapterwillendwithadescriptionoftwodataanalysistechniques,b-gsumminganddouble-pulseanalysisinSections3.6and3.7,respectively.3.2HardwareTheGeDSSDis19-cmindiameter,1-cmthick,andsegmentedinto16by16orthogonal,5-mmstripsonthetwofacesofthecrystal.Thetwosetsofstripsarereferredtoasthe"back"and"front"oftheGeDSSD,andthebeamfromallexperimentsenteredthedetectorthroughthefrontside.Eachofthesestripsisreadoutbytwowithdifferentalow-gainformeasuringtheenergydepositedbystoppingahigh-energyradioactiveion(0-30GeV)andahigh-gainformeasuringtheb-decayelectronandb-delayedtransitions(0-15MeV).TheGeDSSDcrystalissurroundedbyastainlesssteelcryostatwiththinAlwindowsonthefrontandbackapproximately1-mmthickandaninfraredradiationshieldwithanadditional0.143mmeffectiveAlthicknessbetweenthecrystalandthecryostat.ASunpowerInc.StirlingCooler,modelCryoTelMTisusedtomechanicallycoolthecrystal.Thevacuuminsideofthecryostatismaintainedbyanactiveionpump.ThisdetectorwasmanufacturedbyPhDsCo[52]andaschematicdrawingofthisdetectorisshowninFig.3.1.TheGeDSSDwasusedwiththeNSCLDigitalDataAcquisitionSystem(DDAS)[53].TheoutputsweresenttoXIAPixie-16modules[54].Eachmoduleprocessed16channels23Figure3.1AschematicoftheGeDSSD.Thecrystalishousedinthecylindricalregioninthecenteroftheimage,withtheforthetwosetsofstripstothetopandright.Themechanicalcoolerislocatedwithinthebottomrightcylinderoftheimage,andtheionpumpislocatedtoitsleft.ThisisreproducedfromRef.[6].anddigitizedthesignalswitheither100MSPS(MegaSamplesPerSecond)anda12-bitresolution,or250MSPSanda14-bitresolution.Eachchannelwastriggeredindividuallyandrecordedenergy,whichwasextractedviaatrapezoidalalgorithm[55]withuser-controllableparametersandtiminginformation.3.3Energycalibrations3.3.1EnergyextractiontechniquesTheenergiesoftheincidentradiationspulsesareproportionaltothemeasuredpulseheightinthe.ThePIXIE16modules[54]outputanenergyvaluebaseduponinternalpulseprocessingusingatrapezoidal[55].Tracesoftheindividualwaveformswerealsorecordedforofprocessing.Forthecommissioningrunse11503ande09055traceswere6mslongwiththeriseofthesignaloccurring3msintothetrace,whilethetracesrecordedfore11003were2024mslongwiththeriseofthesignaloccurring4msintothetrace.PIXIEusedtwotrapezoidalonefortriggeringandoneforenergyextraction.Thetriggerwasusedtodetecttheleadingedgeoftheriseofapulseandtriggerthesystem.Thesecondslowerwasusedtodeterminetheenergyofthepulse.Inbothcases,thetrapezoidalwascalculatedbysubtractionoftwointegrationregionsseparatedbyagap.TheshapeofthetrapezoidaloutputusedforenergydeterminationisshownschematicallyinFig.3.2.Thefortheenergydeterminationaccountsforthedecaytimeofthesignal[55],whichwasdeterminedforeachchannelindividually.Theequationthatdescribesthefunctionisasfollows:F[i]=a0hiåj=i(L1)Trace[j]i+aghiL)åj=iLG+1Trace[j]i+a1hi(L+G)åj=i(2L+G1)Trace[j]ikB(3.1)wherea0=(b1)L1(b1)L(3.2)ag=1(3.3)a1=1(b1)L1(3.4)b1=exphDtti(3.5)andFisthevalueofthefunctionatpointi,Listhelength,Gisthesizeofthegapbetweenthesubtractedregions,Dtisthesamplingtime,kisaconstantwhichdependsupontheparametersa0,ag,anda1,andBisthebaselineofthetrace[55].Otherofuseralgorithmswereusedonrecordedtracestodeterminetheenergyandidentifyinterestingfeaturesforfurtherinvestigation.Adisadvantageofusinganofalgorithmisalargeincreaseintheamountofprocessingtime,asloopingthrougheachtraceindividuallyiscomputationallytimeconsuming.Anofalgorithmmaybeusedtoseeiftheselectedtrape-zoidalwereoptimized,andcanimprovetheenergyresolutionifthattheparameterswerenotoptimized.Asimpleenergyextractionalgorithmistothehighestbinneartheriseofthetraceand,aftersubtractingthevalueofthebaselineofthetrace,usetheheightasameasureof25Figure3.2Atypicaltracewiththebaselinesubtractedforoneofthebackstrips(bluecurve)andaschematicrepresentationoftheshapeofthetrapezoidaloutput(redcurve).theenergy(Fig.3.3).Alternatively,onecoulddeterminetheareaunderthepulseand,afteragainsubtractingthecontributiontotheareafromthebaselineofthetrace,usetheareaasameasureoftheenergy(Fig.3.4).Whiletheareamethodisalittlemorecomputationallyintensive,summingovermultiplebinslessensthenoiseorunusualtracefeaturescanhaveontheenergyextraction.Theresolutionsofthevariousenergyextractiontechniquesarediscussedinthenextsection.3.3.2High-gainenergycalibration3.3.2.1Commissioningrunse11503ande09055A137Cssourcewasusedtocalibratethedetector,usingaonedimensional(1-D),linearcalibration,wheretheslopeandinterceptweresetindividuallyforeachstrip.Inthecommissioningruns,e11503ande09055,the662-keVgrayandthe32-keVX-raywereusedtocreateatwo-pointcalibration.E(keV)=slope[strip]E(ADCunits)+intercept[strip](3.6)26Figure3.3AtypicaltraceshapeforoneofthebackstripsoftheGeDSSD(bluecurve)andthebaselineheight(green)andthetraceheight(red).Figure3.4AtypicaltraceshapeforoneofthebackstripsoftheGeDSSD(bluecurve)andshowningreenandredareexamplesoftheregionsofthetraceusedtoobtainameasureoftheenergyofthetrace.27ThePIXIEtrapezoidalenergieswereusedfortheenergydetermination.Theresultsfroma137Cssourcecalibrationtakenaftertheverycommissioningrun(e11503)areshowninFig.3.5.Forthefrontstrips,theFWHMofthemiddlestripswasgreaterthanthatofthestripsattheedgesoftheGeDSSD.Forthebackstrips,theFWHMwasmuchmoreconsistentacrossallstrips.Figure3.5The1-Dstripenergycalibrationforthe662-keVtransitionfrom137Csmeasuredim-mediatelyafterthecommissioningrun.ErrorbarsindicatetheFWHMofthepeaks.ThebombardmentoftheGeDSSDwithheavyionscausedradiationdamageandadegradationinenergyresolution.AsshowninFig.3.6,thedegradationwasseenimmediatelyafterofthecommissioningruninthefrontstripsofthedetector.TheentireGeDSSDwasnotilluminatedwithionsduringthecommissioningrunsandsotheedgesofthedetectorretainedtheirinitialresolutionwhilethemiddleofthedetectorwasdamaged.TheresolutionasafunctionofionimplantationforthebackstripsisshowninFig.3.7.IntheGeDSSD,thegeneratedholestraveltothefrontofthedetector,whiletheelectronstraveltowardtheback.TheradiationdamagesufferedbytheGeDSSDaffectedtheholemigrationmorethanthatoftheelectrons[56]byintroducingholetrapping.Thustheresolutionsofthebackstripswerelessaffectedbythebombardmentofheavyions.28Figure3.6Theresolutionsofthehigh-gainstripsintheGeDSSDforthe662-keV137Cstransitionasafunctionofnumberofimplantedionsineachindividualstripforthefewexperiments.Datashownforthefrontsideofthedetector,withtwoedgestripsshownasanexample(strip1and15incircles)andtwomiddlestripsshownasanexample(strips6and9insquare).Theresolutionworsensasthedetectorisbombarded.Figure3.7Theresolutionsofthehigh-gainstripsintheGeDSSDforthe662-keV137Cstransitionasafunctionofnumberofimplantedionsineachindividualstripforthefewexperiments.Datashownforthebacksideofthedetector,withtworepresentativeedgestrips(2and16incircles)andtworepresentativemiddlestrips(8and9insquares).Theeffectsoftheimplantationofbeamarelessnoticeableonthebackstrips.293.3.2.2e11003Subsequentexperiments(e11003)utilizedthefollowingproceduresforenergycalibration.Ener-gieswereextractedfromofpulse-shapeanalysis,utilizingthepulseheightalgorithmdescribedinSection3.3.1.TheenergiesobservedintwoadjacentstripsareplottedagainstoneanotherinFig.3.8toillustratecross-talkeffectsproducedwithinthedetector,whicharisesfromtheelec-troniccouplingbetweenstripsandisindependentofenergyextractionmethod[57].Withasignalinstripi,apulseproportionalinenergyappearsinstripsi+1andi-1,asshowninFig.3.9,wheregatingaroundthe662-keVgrayfroma137Cssourcerevealedthecross-talkpeaksinthetwoad-jacentstrips.Cross-talkmanifestsasaconstantfractionoftheenergyintheadjacentstrip,whichisthecasefortheregionslabeledascross-talkinFig.3.9.Iftheseeffectsweretheresultofchargesharing,whichoccurswhenthechargecloudofaparticleoverlapswithmultiplestripsinthede-tector,theamountofenergywithintheadjacentstripwouldnotbeaconstantfraction,andwouldchangedependinguponthelocationoftheparticlewithinthedetector.Additionally,ifthesig-nalarisingfromagrayfromacalibrationsourceiscalibrated,thecalorimeterspectrum(energyspectrumsummingallthedepositswithinallstripstogether)oftheGeDSSDwillresultinpeaksatslightlyhigherenergiesthantheenergyexpectedfromcalibrationifthereiscross-talkwithinthedetector[57].Theeffectsofcross-talkwerecorrectedbygatingonthefullenergy662-keVgrayanddeterminingthepulseheightintheneighboringstripforeachpairofstrips.Thisonepointcorrectionwasusedtocorrecttherecordedenergiesbyiterativelysubtractingthefractionofthefullpulseheightfrombothneighboringstripsforeachstriprecordinganenergyintheevent.Themultiplicity(beforeandaftercross-talkcorrection)ofbackstripsgatedonthe662-keVpeakfromthe137CssourceisgiveninFig.3.10,wheremultiplicityisthenumberofstripswithanenergyabovethresholdwithinasingleevent.Aftercross-talkcorrection,thestripswerecalibratedusingseveralgrays:the59.5-keVgrayfrom241Am,the662-keVgrayfrom137Cs,the1173-keVand11332-keVgraysfroma60Cosourceandseveraladditionalbackgroundgrays(40K:1460keV,208Tl:1592-keVescapepeak30Figure3.8Theuncalibratedenergiesoftwoadjacentstripsformultiplicity3eventsfroma137Cssourceonthebacksideofthedetector.Theeffectsofcross-talkappearintheregionsontheedgeofthefrom2615keV)visibleintheGeDSSDspectrumduringaweekofrecordingdata(Fig.3.11).Nodriftinthepeakpositionswasobservedasafunctionoftime.Withthe1-Dcalibration,itwasapparentthatthecalibrationforasinglestripononesideofthedetectorwasdependentuponthepositionoftheeventintheoppositesetofstrips,asshowninFig.3.12.Thiseffectwasseenacrossstripsonbothsidesofthedetector,indicatingthatboththefrontandthebackoftheGeDSSDrequiredatwodimensional(2-D)energycalibration.A2-Dcalibrationtakesthepositioninbothsetsofstrips,apixel,asthepositiontocalibrateby.E(keV)=slopeback[stripback][stripfront]E(ADCunits)+interceptback[stripback][stripfront](3.7)E(keV)=slopefront[stripback][stripfront]E(ADCunits)+interceptfront[stripback][stripfront](3.8)Whencalibratingthebackstrips,thepositionoftheeventonthefrontwastakenasthestripcentroid(andvice-versa).Forexample,ifthebackstripsregisteredenergiesabovethresholdinstrips7and8,ifthefrontstripcentroidwasinstrip9,thenthetwocalibratedpixelswouldbe7,9,and8,9.Theneedfora2-Denergycalibrationarosefromtheradiationdamagewithinthedetector,asaresultofchargetrapping.31Figure3.9(a)Therawenergyhistogramformultiplicity3eventsforfrontstrip5.Gatingaroundthepeakat1650ADCunits,correspondingtothefull137Csenergydeposition,(b)theeffectsofcrosstalkcanbeenseenintheneighboringstrips,strip6showninblueandstrip4inred.32Figure3.10Multiplicityofthebackhigh-gainstripsgatedonthe662-keVgrayfrom137Cs.Inredisthemultiplicitybeforecross-talkcorrection,andinblueisthemultiplicityaftercross-talkcorrection.Figure3.11Calibratedstripenergyspectrumforallbackstripsonthedetectorshowingthehigherenergycalibrationpeaks.33Figure3.12Dependenceofbackstrip8cross-talkcorrected,energycalibrated137Csspectrumonthecoincidentfrontstrip.Theiszoomedinaroundthe662-keVtransition.The2-Dcalibrationwasdeterminedpixelbypixel(whereapixelisastheintersectionofthestripsonbothsideofthedetector)withalinearcalibrationbaseduponthe662-keV137Csand59-keV241Ampeaks.Eachpixelpositionhadtwocalibrations;oneforthebackstripandoneforthefrontstrip.Thetwocalibrations(1-Dand2-D)arecomparedinFig.3.13forthesamestripshowninFig.3.12.Thus,comparedtothecommissioningruns,thecalibrationtechniqueforthehigh-gainstripshadtoshiftfromaonedimensional,linearenergycalibrationtoamulti-stepcalibration,consistingofcross-talkcorrection,followedby1-Dcalibration,andthe2-Dcalibration.The137Csand241Amcalibrationdatawastakenfor3hoursaftertheendofthebeamtime,waitinguntileachstriponbothsideshadseveralhundredcountswithinthe662-keVpeakinordertocheckthecalibrationandconditionoftheGeDSSDafterbeingexposedtomorebeam.Sincethepixelsattheveryedgeofthedetectorhadalimitednumberofcounts,thisnecessitatedtheuseofa1-Dstripcalibrationbeforethe2-Dpixelcalibrationtoinsurethatnopixelswereleftuncalibrated.TheresultingresolutionsfromthisapproacharedisplayedinFig.3.14.IncomparisontoFig.3.6,forthesamestrips(1and9onthefront),theresolutionfromthe2-Dcalibrationusingthepulse34heightenergyextractionalgorithmwassimilartothatfromthe1-DcalibrationusingthePixieenergiesforstrip9inthemiddleofthedetector(˘17keVfromthePIXIEenergiesvs.˘15keVforthepulseheightenergies).Asthestripontheedge(1)wasexposedtobeam,itsresolutionwaspoorerinFig.3.14comparedtothatoftheearlierexperiments,inwhichthestripwasnotyetexposedtoanybeam.Thiswouldsuggestthatmostoftheresolutiondegradationoccurredafterthebeamexposure,withlessdegradationuponfurtherbombardment,whichisevidencedinFig.3.6wherethemiddleofthedetector'sresolutionremainsroughlyconstantaftersomeionsimplanted.Figure3.13Calibratedbackstrip8energyspectrumcomparingthe1-Dcalibration(red)tothe2-Dcalibration(blue).3.3.2.3Re-analysisofe11503Thetechniquesdevelopedinlaterexperimentswereusedtore-analyzetheresolutionsandcalibra-tionfromtheearliestdatasets.Someresolutioncanberecoveredbypulseprocessingandcorrect-ingfortheeffectswithintheGeDSSDinvestigatedduringe11003.Thesourcedatatakenaftertheexperiment,e11503,wasre-investigatedtodetermineifimprovementscouldbemadetotheresolutionafterbeamdepositionintothedetector.MovingfromPIXIEenergiestopulseprocess-35Figure3.14ResolutioninkeVofindividualstripsaftercalibrationthepixelsofthedetectorwitha137Cssourceafterexperimente11003.ingfortheenergydetermination,withnootheranalysis,animprovementinresolutionwasseenacrossstrips(Fig.3.15).After1-Dcalibration(withthepulseheightenergydetermination),thebackstripenergyvs.frontstripnumberforthesamestrip(strip8)asFig.3.12isshowninananalogoushistograminFig.3.16.Thedependenceupon2-Dpositionismuchlessthanthatfordatatakenfromlaterexperiments,duetolessdamage.ComparingthedataforstripsshowninFig.3.7,thepulseheightanalysisfora137Cssourceaftere11003(Fig.3.14)yieldedresolutionsof12keVinstrip9and7keVinstrip2,whereastheresolutionsshowninFig.3.15aresimilar(9keVinstrip9and8keVinstrip2).ThePIXIEresolutionsinFig.3.7alsocomparefavorablytothoseinFig.3.15.Theresolutionsofbackstrips2and9aresummarizedinTable3.1.Forthetwoexperiments,differentPIXIEmoduleswereused(100MSPSfore11503and250MSPSfore11003),andasaresult,thePIXIEtrapezoidalparameterswerenotthesame.36Figure3.15Resolutionofbackstripsfromraw(non-calibratedorcross-talkcorrected)energyspectracomparingenergiescalculatedbythePIXIEtrapezoidal(blackcircles),pulseheightalgorithm(redsquares),andpulseareaalgorithm(bluediamonds)forthe662-keVpeakfroma137Cssource.Thesedataweretakenimmediatelyafterexperimente11503.Figure3.16Frontstriplocationvs.backstripenergycalibrationforthere-analyzeddataaftere11503forthe137Cssourceat662-keV.Amuchsmallervariationwithincalibrationasafunctionofstriplocationontheothersideisseencomparedwiththelaterdata.37Table3.1Resolutionsofstrips9and2onthebacksideofthedetectorontheshowninthissection.StripFigureEnergyExtractionResolution93.7PIXIE5.48-15.83.14PulseHeight12.03.15PIXIE13.7PulseHeight8.50PulseArea5.5623.7PIXIE5.00-14.73.14PulseHeight7.303.15PIXIE13.6PulseHeight8.22PulseArea4.693.3.3Low-gainenergycalibration3.3.3.1Commissioningrunse11503ande09055Thecommissioningrun(e11503)useda130Mev/A76Gebeamwitha423mg/cm2Betarget,witha0.5%momentumacceptanceintheA1900spectrometer[41].ThisbeamwasfragmentedtoproduceMn,Fe,CoandNiisotopeswithA˘68andwascenteredontransmitting67Fe.Formoreexperimentaldetails,pleaseseeSection3.4.2.2.Inthecommissioningexperiments,thelow-gain(orimplant)signalsweresimplygain-matchedbaseduponthePIXIEenergyextraction.Thestripenergywascalibratedbasedontheenergydepositionof67mFe[58].Thesubsequentg-rayemissionfrom67mFeat367keV(t1=2=0.730(31)ms)providedacleantagfor67Feions.Theenergypulsesweregainmatchedaccordingtothefollowingequation:E(MeV)=LISE(MeV)Eimplant(ADCunits)[strip]E(ADCunits)(3.9)whereLISE(MeV)istheLISE[59]predictionoftheamountofdepositedenergybya67Feion,EimplantistheamountofenergyinADCunitsdepositedbyan67FeioninagivenstripandEisthecurrentenergydepositionbeingcalibrated.Forthestripswiththemostbeamintensityinthemiddleofthedetector,Fig.3.17showsthecalibrationtodemonstratetheeffectsofgainmatching.38Thestructuresintheenergyspectrumweretheresultofdifferentionsdepositingdifferentenergiesinthedetector.Figure3.17Calibrationofthelow-gainstripsutilizingthegainmatchingtotheLISEpredictedenergiestechnique.Showningreen,redandblueareshowntheeventsforstrips8,9,and10,respectively.3.3.3.2e11003Ine11003,thecalibrationofthefrontlow-gainelectronicsfollowedasimilarpatterntothatofthehigh-gainstrips,calibratingtheenergywitha124SnbeambaseduponLISEenergycalculations.Onthebacksideofthedetector,thesaturatedandthusthosestripsweresimplygainmatched,asthelocationinADCunitsforthesaturatedstripswasalittledifferentfordifferentstrips(makingthepeaksfromtheiondepositionslightlydifferentbetweenstrips,necessitatingthegainmatching),usingthePIXIEenergiesinlieuofpulseprocessing.AnexampleofasaturatedpulseisshowninFig.3.18.Manyioneventssaturatedmorethanonestriponthebacksideofthedetector.Therefore,thestripsonthebacksideofthedetectorwereusedtodeterminethepositionoftheeventbyanenergyweightedaverageofthestripnumber,butwerenotusedforanenergycalculation.Thedistributionofstripsonthebacksidetendedtobesymmetrical,witha39few(typically1-3)saturatedstripsatthemiddleofthedetectorandastriponeithersideofthatdistributionfromelectroniccross-talk.Theenergydepositedbytheionswasgreaterine11503thanthatintheothertwoexperiments.Figure3.18AnexampletracefromthebackoftheGeDSSD(blue),illustratingthesaturation.Themaximumamplitudeis16384,whereasthelow-gainbackstripsreachamaximumwellbeforethemaximumoftheADCrange.Forcomparison,atracefromthefrontoftheGeDSSDisshown(red).Onthefrontstrips,cross-talkcalibrationwascompletedusingthesametechniquesaswiththehigh-gainelectronics.A124Sn50+beamwasutilizedforthispurpose.ThetwodimensionalplotofenergiesoftwoadjacentstripsisshowninFig.3.19.AnalogoustoFig.3.8,depictingthehigh-gainstrips,theeffectsofcross-talkcanbeseenintheregionsonthesidesoftheChargesharingisobservedinthecenterofthespectrumandoccurswhenthechargecloudcreatedbyaparticleoverlapswiththegapbetweenadjacentstrips[60].Energyfromtheparticleisdepositedintobothstrips.Thisisdistinctfromtwoparticlesdepositingtheirenergiesindividuallyintotwoadjacentstrips.Whilenotimplementedinthisanalysis,onecouldconsidersummingchargesharingeventstorecreateasingleenergydeposition.IncomparisontoFig.3.8,thechargesharingregioninFig.3.19haddiscontinuitiesinsteadofbeingstraightacross.Onepossibleexplanationliesinthedifferenceinenergylossbetweentheheavyparticlesandgrays.Theenergylossacrossthecrystal40islowerforgrays,andtheparticlescanpenetratethroughtheentirethickness.Theheavyionsstopaverysmalldistanceintothecrystal,losingalargeamountofenergy.Theconnectionsoftheelectrodestothecrystalmakeupagreaterproportionofaparticle'spathfortheheavyions,andthereforethereareenergylosses.Inthecharge-sharingregion,someofthechargecloudoverlapswiththegapbetweenadjacentstrips,andthereislessenergyloss.Figure3.19A2-Dplotofneighboringstripsshowingcross-talkandchargesharing.Thesubsequentoneandtwodimensionalenergycalibrationswerecarriedoutinthesameprocedureastheirhigh-gaincounterparts.InFig.3.20,theonedimensionalenergycalibrationofstrip4onthefrontofthedetectorisshownasafunctionofthelocationinthebackstrips.Likethehigh-gainelectronics,thecalibrationdependsuponthe2-Dlocationwithinthedetector.InFig.3.21,thedifferencebetweenthe1-Dand2-Dcalibrationisshown.Whiletheabovetechniquesworkwellforthesidestrips,whichhaveseenlessiondeposition,themiddlestripsbecamedamagedandthecalibrationwasmoredifInthemiddleoftheGeDSSD,thefull-energydepositionpeakisnotclearandsocalibrationsweremadebaseduponeventsthathadmultiplicity1aftercross-talkcorrection,whichwereassumedtoconsistofthefull-energy-depositionpeakandcross-talkpeaksinstripsononeorbothsides.Highermultiplicityeventusedthemultiplicity1calibration,andwerenotthrownaway.Thecalibrated41Figure3.20Backstriplocationasafunctionofenergyinfrontstrip4showingthedependenceincalibrationonlocationindetector.Figure3.21Acomparisonofrecordedenergydepositionfromthe124Sn50+beambetweenthe1-Dcalibration(red)tothesubsequent2-Dcalibration(blue)forfrontstrip4.42spectrumforastrip7isshowninFig.3.22inblue,whilethemultiplicity1aftercross-talkeventsareoverlaidinred.Highermultiplicitiesdonothaveapparentpeaks,asisshowninFig.3.23.Themultiplicitydistributionbeforeandaftercross-talkcorrectionforallfrontlow-gaineventsisdisplayedinFig.3.24.The2-Dhistogramoftheenergyinadjacentstrips8and9inthebeamimplantationisgiveninFig.3.25.Theregionsonthesidesoftheplotresultingfromcross-talkbetweenstripsarestillrelativelyclearbutthecenteroftheplotwherecharge-sharingwouldbeexpectedisnotasclearasthatseenintheedgestripsofthedetector(Fig.3.25).Anotherwaytovisualizethiseffectistocomparetheresultsforthefully-strippedSnionsbeforeandafterthebeamtime.InFig.3.26,apeakisvisibleinthedataatthestartofthebeamtimebutnotattheend.Figure3.22Thecalibratedenergyforastripinthemiddleofthedetector,strip7.Allmultiplicities(blue)andmultiplicity1aftercross-talkcorrection(red).Finally,therewasalsoagain-matchingappliedforthelatertwosettings(centeredonRuandNbisotopes,seeChapter4)toaccountforanysmallshiftsincalibrationduringthebeamtime.Thiswasdonefortworeasons:totrytoimprovetheresolutionasmuchaspossible,andbecausethecalibrationforthe124Snbeamwasslightlydifferentfordatatakenatthestartoftheexperimentandtheend.Thecalibrationwascompletedusingthe124Snbeamattheendoftheexperiment43Figure3.23Themultiplicitydistributionasafunctionoftheenergyofstrip7.Figure3.24Themultiplicitydistributionsoffrontlow-gaineventsine11003,beforecross-talkcorrection(red)andaftercross-talkcorrection(blue).44Figure3.25A2-Ddistributionoftheenergyobservedintwoneighboringstripsinthemiddleofthedetector.Figure3.26Acomparisonoflow-gainstrip7inthe124Snfully-strippedbeambefore(red)andafter(blue)thedurationofthebeamtime.Thefull-energydepositionisnotclearinthedataaftertherestoftheexperiment.45andusedfortheprecedingweek'sbeamtime.Fortwo-thirdsofthestrips,theshiftincalibration,relativetotheaveragevalue,waslessthan2%(withenergiesontheorderof5.5GeV).Fig.3.27illustratesthedegreeofthisgainshiftforeachofthestripsonthefront,forbothofthebeamsthatfollowedthe124Snbeam(seeChapter4formoredetailsontheexperiment).Thisshiftwascorrectedasafunctionoftime.Figure3.27Relativeshift(comparedtotheaveragevalueacrossallstrips)intheenergycalibrationasafunctionofstripnumber,shownforthetwolaterbeamsettingsine11003.Aspreviouslymentioned,theGeDSSDsustaineddamageduetotheimplantationofheavyions.Thiseffectmanifestedinavarietyofdifferentways:adegradationofresolution,theneedfora2-Dcalibration,andthelossofanobservedfull-energypeakinthemiddleofthelow-gainstrips.Whilethedegradationinresolutionoccurredimmediately,theothereffectsworsenedovertime.Theeffectsofneutrondamagedwithinsegmented,planarGedetectorshasbeenpreviouslystudied[61].Forneutrondamage,thecrystallatticeofthecrystalbecomesdisordered,whichresultsinvacanciesinthecrystal.Thedisplacedatomscreatechargetrapping,whichisgreaterfortheholecollection.Thisresultsinthelossofeventswithinthedamagedregionofthedetector,wherefullenergydepositionisnotobserved.TheseeffectsaresimilartowhatwasobservedafterthebombardmentoftheGeDSSDbyheavyions.463.4SimulationsplayedalargeroleinquantifyingtheefyoftheGeDSSDsinceastandard-izedsourcecannotbeplacedatthelocationwithinthegermaniummaterialfromwhichradiationoriginates,thoughifanisotopewithwell-knowng-rayabsoluteintensitiesoverarangeofener-giescanbeproducedanddeliveredtotheexperimentalstation,onecouldmeasureefThedetectionefywasmeasuredusingasourceexternaltotheGeDSSD'scryostatandwasmatchedwithsimulationtoverifytheaccuracyofthesimulation.ThenthesimulationwasusedtoobtainthedetectionefyfromalocationinsidetheGeDSSD'scrystal.Off-lineefymeasurementsforasourceexternaltotheGeDSSDcryostatwiththegermaniumdetectorsutilizedintheexperimentsdiscussedinthisdocumentwereperformedusingaNISTcalibratedStandardReferenceMaterial(SRM)154\155Eusource,SRM4275C-69.3.4.1AbsolutegrayTheefyoftheGeDSSDwasmeasuredforanSRMsourceplaced2.4cminfrontoftheGeDSSDentrancewindow.ThecomparisonbetweensimulationandexperimentisshowninFig.3.28,withsimulationmatchingquitewellatenergiesabove100keV.ThesimulationwasthenusedtodeterminetheefyofgraysfromanionlocationafewmillimetersinsidetheGeDSSD.IonswereexpectedtostopwithinathefewmillimetersoftheGeDSSDdependingupontheionandtheenergyofthebeam,forexample,LISEcalculationsindicatedanexpectedimplantationdepthbetween1-2mmintotheGecrystalfortheionsinbothe11503ande09055.Fore11003,LISEpredictedimplantationdepthsbetween0.5and1mm.Fig.3.29showsthesim-ulatedefforimplantationatdepthsof1and2mmintheGeDSSD.TheGeDSSDisquiteefforlow-energygraysbuttheefyquicklydropsbelow5%at500keV.TheefpresentedinFig.3.29weresimulatedforanisolatedg-raysource.Thepres-enceofb-decayelectronswillreducetheefyofg-raydetectionintheGeDSSDastheenergydepositionbythebandgparticleswithinasinglestripwillsumtogether.Thiseffectis47Figure3.28Comparisonofsimulatedandexperimentaleffroma154,155EuSRMsourcelocatedoutsideoftheGeDSSD'scryostat.Theisreproducedfrom[6].Theefyshownisapeakefy.ThetotalnumberofcountsineachpeakintheSRMsourcewasdeterminedforeachstripindividually,andtheresultsfromeachstripweresummedtotheefencyplottedintheFigure3.29graydetectionefyoftheGeDSSD.Simulatedfortwoimplantationdepths.TheisreproducedfromRef.[6].Theefyshownisapeakefency.Thetotalnumberofcountsineachsimulatedenergywasdeterminedforeachstripindividually,andtheresultsfromeachstripweresummedtotheefyplottedinthe48discussedinmoredetailinSection3.6.3.4.2ElectronAnotherimportantconsiderationistheefyfordiscreteelectrontransitions,analogoustothedetectionofanisolatedgray.Thisefyisnecessaryforconversionelectronspectroscopyfollowingisomericdecays.Arelatedefyistheelectroncorrelationefy,whichisthepercentageofb-decayelectronsnotonlydetected,butsuccessfullycorrelated(ormatched)totheprecedingionthatemittedit.Theelectroncorrelationefydependsuponoverallimplantationrate,theelectronefy,anddecayhalf-life.3.4.2.1ElectrondetectionTheGeDSSDshouldbehighlyeffordetectingelectrons,makingitanidealconversionelec-trondetector.Forelectronswithenergieslessthan500keV,theGeDSSDisnearly100%efAstheenergyoftheelectronincreases,sodoestherangeoftheelectronandtheabsoluteefyfordetectingthefullenergyoftheelectrondecreases.For1mmand2mmimplantationdepths,thecalculatedefyfordetectingtheenergyoflow-energyelectronsinthesamestripastheionisshowninFig.3.30.Thesimulatedsourceofelectronswasuniformlydistributedacrossavebyvemmarea(thesizeofasinglepixel)andwasplacedinthecenterofastripatthemiddleofthedetector.Thesourcewasassumedtoemitelectronsisotropically.Theobserveddropinefciencyathigherenergieswasduetotheelectrontravelingbeyondasinglestrip,depositingenergyintomultiplestripsorfromelectronsescapingfromthefaceoftheGeDSSD.Greaterimplantationdepthsincreasestheefyathigherenergies,duetofewerelectronsescapingoutofthefaceofthedetector,toapoint.TheefyasafunctionofdepthintotheGeDSSDfor3000keVelectronsissummarizedinTable3.2.Nearthemiddleofthedetector,theefyislessdepen-dentuponthedepth,astheelectronshavepenetratedfarenoughinsidetolimittheirescapeoutoftheGeDSSD.49Figure3.30Efyfordetectinglow-energyelectronsforimplantslocatedat1mm(black)and2mm(red)fromthefrontfaceoftheGeDSSD.Theefywasdeterminedbythenumberofcountswithinthepeakatthefullenergyofthesimulatedelectronsforthestripinwhichelectronoriginated.Table3.2ElectrondetectionefyasafunctionofdepthintotheGeDSSDfor3000keVelectrons.Theefywasdeterminedbythenumberofcountswithinthepeakatthefullenergyofthesimulatedelectronsforthestripinwhichelectronoriginated.Depth(mm)Efy(%)Uncertainty(%)149.60.3265.50.4368.90.4569.40.4503.4.2.2b-decayelectroncorrelationInordertodeterminetheGeDSSD'selectroncorrelationefy,54Niionsproducedduringexperimente09055werestudied.Thesecondcommissioningexperiment(e09055)useda160Mev/A58Nibeamwitha520mg/cm2Bewedge.HerethemomentumacceptanceoftheA1900was1%,toproduce54Niand55Cu.Theionswereproduced,separated,andtransmittedtotheexperimentalarea.TheionspassedthroughtwoPINdetectors(303and488mmthick)tomeasuretheirenergylossandTOFrelativetotheA1900.TheionsthenpassedthroughathinKaptonwindowattheendofthebeampipeandafewmmofairbeforegoingthroughtheGeDSSDcryostatandstoppingafewmmintothecrystal.TheGeDSSDwassurroundedwiththeSegmentedGermaniumArray,orSeGA[50],todetectb-delayedg-rays.SeGAwasarrangedintworingsofeightdetectors,oneupstreamoftheGeDSSDpositionandonedownstream.Thewassimilartothestandardb-SeGAlayout[62],butwitha11.6cmspacerbetweenthetwohalvesofSeGAtoaccommodatetheincreasedwidthoftheGeDSSDcomparedtosmallerSiDSSDsetups.PhotographsoftheexperimentalsetupareshowninFig.3.31andFig.3.32.Figure3.31AphotographoftheGeDSSDandSeGAionusedforexperimentse11503ande09055viewedfromtheside.Thebeamtravelslefttorightintheimage.ElectroncorrelationefyisonewaytocomparetheincreasedperformanceoftheGeDSSDtoitsmoretraditionalSicounterparts.Dependingupontheions'half-livesandtheexperimental51Figure3.32AphotographoftheGeDSSDandSeGAionusedforexperimentse11503ande09055.Thebeamexiststhepagetowardtheviewer.implantationrate,Si-basedsystemsexhibitacorrelationefyof30-40%[6,42].Giventhehighimplantationraterelativetotheions'half-livesinexperimente09055,correlationsweremadeallowingonlydecaysinthesamepixelastheimplanttobecorrelated.Awidercorrelationwasnotusedduetotheincreaseinrandomcorrelations.Fig.3.33showstheb-decayhalf-lifecurveforthe54Niions,whereahalf-lifeof97(2)mswasextractedusingtheBatemanequations.Theparameterswithinthethatwerevariedweretheparentdecayconstant,theactivityoftheparent,andtheconstantbackground.Thedecayconstantofthedaughternucleuswasinputintothebutkeptasaconstant.Thehalf-lifeof54NiwasextractedfromtheparentdecayconstantoftheThewasperformedusingachi-squaremethod.Previousresultsreport106(12)ms[63]and103(9)ms[64]forthehalf-life.Themaximumcorrelationtimewaschosentobe500ms,whichisroughly5half-lives.ThedecaycurvewaswiththeBatemanequationsforradioactivedecay,wherethecontributionsfromtheparent54Ninuclei,thedaughter54Conuclei(t1=2=193.23ms[63]),andaconstantbackgroundarealsoshown.Thenumberof54Nidecayswasextractedandcomparedtothetotalnumberofimplantedionstogiveanelectroncorrelationefyof55(2)%.Simulatingthisdecay,anelectroncorrelationefyof61.6(6)%waspredictedforsame-pixelcorrelations.Whilethe52experimentaldatadidnotallowforanexpansionintoawidercorrelationsimulationpredicteda87.0(7)%efyforanexpandedcorrelationFigure3.33Decaycurveof54NiandthewiththeBatemanequations,whichwasusedtodeter-minetheelectroncorrelationefy.Thedecayofthe54Niparentisshowninpink,thegrowthanddecayofthe54Codaughterisshowningreen,andthecontributionfromthebackgroundisshowninblue.Theisreproducedfrom[6].Thedifferencebetweensimulationandexperimentarisesfromthedetailsofthesimulation.Theoriginalsimulationwascompletedusingapointsourceofelectronsatthecenterofapixel.Foradistributedsourceofelectronsacrossapixel,thenumberofeventswheretheelectronandionwouldbefoundinthesamepixeldropsby10%.3.5b-decayspectroscopytechniques3.5.1TriggeringThereareseveraltriggeringschemesthatmaybeusedwiththeGeDSSD:freerunning,exter-nalvalidation(front-backcoincidence),andforcerecordingforallchannels.Inthefreerunningscheme,eachchanneltriggersindependentlyandrecordsitsdatatotheinternalmemorybufferof53theelectronicsmoduleforeventreadoutandeventassembly.Intheexternalvalidationmode,anexternalvalidationsignalmustarriveincoincidencewithadelayedcopyofthechannel'sinternaltrigger.ThismodeisusedtoselecteventswherebothafrontandbacksignalarepresentfromtheGeDSSDallowinglocalizationtoasinglepixel.ThetriggeriscreatedfromalogicalORsignalofthe16frontstripsonthedetectorwithalogicalANDtotheORofthe16backstrips.TheANDsignalisfedbackintothemodulesastheexternaltrigger.Finally,thesystemmayalsoberunwithanexternaltriggerforcingallchannelsinamoduletorecorddatawhenevertheexternaltriggerisapplied,regardlessofwhetheranindividualchannelhasobservedasignaloverthresholdornot.Notunexpectedly,thisthirdmoderesultsinalargeamountofdata.Theforcedtriggermodecanbehelpfulforaligningthestartoftracesintime.Allexperimentsdiscussedinthepresentworkusedthesecond,front-backcoincidencemodefortheGeDSSD,whilethefree-runningmodewasusedfortheancillaryg-rayarray.3.5.2EventlocalizationTheheavyionsproducedbytheCoupledCyclotronFacility(CCF)stopped,orimplanted,afewmillimetersintotheGeDSSD.Thiseventisreferredtoasan"implantevent"andwasbythepresenceofsignalsinthelow-gainelectronicsoftheGeDSSD,thePINs,andTOFin-formation.Therewillalsobeovwsignalsinthehigh-gainelectronicsoftheGeDSSD.Atiminggatebetweenthefrontandbackstripsinthedetectorwasalsoplacedupontheevent.Thechargedepositedbytheheavyiontravelstoeithersideofthedetectorontheorderof100nsfor1cmofGe[65],soeventswithlargertimingdifferenceswereunphysical.Thetimingdifference(back-front)betweensignalsonthetwosidesofthedetectorasafunctionoffrontstripenergyisplottedFig.3.34.Eventswithenergiescorrespondingtothefullionimplantenergywerecloselygroupedatsmall,positivetimingdifferences.TheblackgateinFig.3.34isthetimingandenergygateplacedonthelow-gainevents.Inthethelowerenergyregioncorrespondstoeventswithwhatappearedtobecross-talkpeaksinmultiplicity1events,andalsopotentiallylightionsproducedbythebeamfragmentation.54Figure3.34Backstriptimingminusfrontstriptimingvs.frontstripenergy(cross-talkcorrectedand2-Dcalibrated)forimplantevents.Theblackgateshowsthecutplacedonthelow-gainevents.TheeventsshowninthedonotrequireaDEsignalwithinthePINs.TheradioactiveionsimplantedintotheGeDSSDsubsequentlybdecay.Theb-decayelectronwasdetectedbytheGeDSSD,andb-delayedgraysweredetectedbyeithertheGeDSSDoranancillaryGearray.Aneventofthistypeisreferredtoasa"decayevent".AdecayeventwasifthereisnoenergydepositedintothePINsorlow-gainsignalsoftheGeDSSD,andtheremustbeasignalabovethresholdonbothsidesoftheGeDSSDinthehigh-gainelectronics.Aswiththeimplantevents,atiminggatewasplacedonthedifferenceintimebetweenthefrontandbackstrips.ThedistributionoftimingdifferencesisdisplayedinFig.3.35,andagateof0.8mswasplacedonthedecayevents.Thevastmajorityofeventsfellwithinthistiminggate,with99.99%oftheeventsonthefrontandbackofthedetectoroccurringwithin0.8msofoneanother.AnalogoustoFig.3.34,theenergyvstimingdifferencefordecayeventsisplottedinFig.3.36forthefrontandbackofthedetector.TheFWHMforthetimingdistributionis0.112ms.Inanevent,morethanonestripwithintheGeDSSDcanrecordanenergy.Inordertothelocationoftheevent,theweightedaverageoftheenergiesofthestripsistakentodetermine55Figure3.35Backstriptimingminusfrontstriptimingfordecayevents.Thetiminggateisinblackonthetheeventlocation:maxch=16åi=1iE(i)16åi=1E(i)(3.10)wheremaxchisthestripnumberofthestripcentroid(roundedtothenearestinteger),iisthenumberofthestripandE(i)istheenergyofstripi.Thelocationoftheeventwasdeterminedbytheenergycentroidonbothsidesofthedetectorandcorrespondedtoapixelwithinthedetector.Thepixellocationofaneventwasusedalongwithtiminginformationtocorrelateimplantstotheirsubsequentdecayevents.Decaysmustoccurwithinthesamepixeloroneoftheeightclosestneighboringpixelsasaprecedingimplantandwithinatimingwindow(thecorrelationwindow),whichwaschosendependingontheimplantationrateandthehalf-livesoftheproducednuclei.Typically,acorrelationwindowwaschosenontheorderof2-3half-lives.Formoredetailsabouttheefyofcorrelation,seeSection3.4.2.2.56Figure3.36Energyofthestripchosenastheeventlocationvs.thehigh-gaintimingdifferencefor(a)frontstripsand(b)backstrips.573.6b-gSummingGiventhehighefyfordetectinglow-energygrays,itispossiblethattheb-decayelectronandb-delayedgrayscoulddeposittheirenergiesinthesamelocationwithinthedetectoratthesametime,thussummingtheirenergiesintoasingle-pulse.Analgorithmtocorrectforthiseffectisdiscussedinthissection.Theb-gsummingeffectismitigatedwhenstudyingisomericstatessincethehalf-lifeofthemetastablestateprovidesadelaybetweenb-decayelectronandsubsequentisomericgrayorconversionelectronelectron,separatingthemintime.Thealgorithmtocorrectfortheeffectsofb-gsummingwasdevelopedviasimulation,andpreliminarilyvbyexperiment.Inthecommissioningrune11503,67Fewasproduced.Thisdecaypopulatesa680.5-keVstatewhichdecaysviaa188.9-keVtransitionin67Co[66]toalong-livedisomericstate.Thistransitionwaswell-suitedtostudyingb-gsummingalgorithmsduetothehighefyfordetectionofagrayat189keVwithintheGeDSSDandtheabilitytodetectcoincidentfeedingtransitionsinSeGA(Fig.3.37).Foranisolatedgray(intheabsenceofb-gsumming),theefyoftheGeDSSDat189keVwas27.5%forthestripsofthedetectoronasingleside(seeFig.3.29)baseduponsimulation.Theadditionalpresenceofab-decayelectroninthesimulationdroppedthisefyto10%,becausetheenergyfromtheelectronwillprimarilybedepositedinthestripwheretheionwaslocated,preventinganygraysfrombeingseparatelydetectedwithinthatstrip.Iftheelectrontravelsbeyonditsinitialstrip,thosestripswouldalsosumwithanyg-rayenergydeposition,preventingdetectionofthegray'sfull-energypeak.Forhigh-energyelectrons,theelectronswillloseanywherefrom10'sofkeVuptothetotalenergyoftheelectroninasinglestrip.ThisresultsinawidedistributionofenergieswithinasinglestripoftheGeDSSD.3.6.1DevelopmentoftechniqueinsimulationInordertotrytoseparateenergydepositionsduetob-decayelectronsandb-delayedgrays,thetwodimensionalcapabilitiesofthedetectorwereutilized.Recallthateachstripreadsoutan58Figure3.37Partiallevelschemeandfeedingin67Co.DataaretakenfromRef.[66].energyindependently,andthepixelnumberwasusingthefrontandbackstripsinsoftwareasthelocationoftheevent.Alternatively,theeventlocationcanbeas(1)thestriponbothsidesofthedetectorwiththegreatestamountofenergydeposited(e11503ande09055)or(2)thestripcentroid(e11003).Ifmorethanonestriponasiderecordedanenergyabovethreshold,multiplepixelscouldbeassignedanenergydepositionbuttheconversionbetweenmultiplestripsandmultiplepixelsisnotnecessarilyunique.Thepositionalgorithmconsidersseveraldifferentcasesbasedonthestripmultiplicityonthetwosidesofthedetector(Table3.3).Theenergydepositionsoneachsidewereorganizedintoarraysorderedbydescendingenergy,andtheenergyofsinglestripsandsumsofstripsononesideofthedetectorwerecomparedtotheenergyofsinglestripsandsumsofstripsontheothersidetocombinationsofmatchingenergies.Someofthepossiblecombinationsofstripenergieswillnotbeuniqueand,insomecases,severalreconstructedpositionswerepossible.Thisapproachassumedthatthetotalamountofenergydepositedonboth59sidesisthesame,i.e.xåi=1ES1(i)=xåi=1ES2(i),whereE(i)representstheenergyofasinglestripandS1andS2denotethetwosidesofthedetector.Table3.3Descriptionofstriparrangementsandpossiblepixelreconstructionintheb-gsummingalgorithmSide1Side2DescriptionofEnergyRelationshipMultiplicityMultiplicityStripArrangement11PixelatintersectionofstripsES1=ES21x>1SinglestripononesidesplitintoxpixelsES1=xåi=1ES2(i)22Energysplitby2by2boxSeetextTwomatchingenergyde-positionsES1(1)=ES2(1);ES1(2)=ES2(2)2x>2One-to-onestripmatches,singlestriptosumofmul-tiplestripsCheckformatchingstripsintheabovepatternsy>2x>2Manypossiblearrange-mentsCheckformatchingstrips(s)intheabovepatternsThescenariosdescribedinTable3.3aredepictedschematicallyinFig.3.38,Fig.3.39,andFig.3.40.IneachadiagramoftheGeDSSDdividedintostrips,andtheintersectionofstripsisapixel.ThestripsarelabeledattheedgewiththeenergiesinthenotationusedinTable3.3,andthepixelsarelabeledwithinthediagramwiththepixelenergiesderivedfromthestripenergies.Foreventswithmultiplicitiesgreaterthan1onbothsides,thealgorithmsearchedformatchingsumsonbothsidesoftheGeDSSDinthesepatternsuntilasmanyofthestripenergiesaspossiblewereplaced.Anyremainingstripswereleftasstripenergiesandwereaddedtotheoutputspectraontheirown.Whenonesidehadamultiplicityof1,thepixelassignmentwasgenerallyunambiguous,asallenergiesontheoppositesidemustsumtotheenergyofthesinglestrip.Inafewcases,theenergyofmultiplestripswassplitamongseveralpixels.Theofthesepossibilitieswaswhenbothsideshavemultiplicity2.Iftheindividualenergiesdidnotmatchonbothsides(seeFig.3.40),thenthisenergywassplitbetweenthepixelsencompassingthe60Figure3.38Anillustrationofthestriparrangementsandpixelreconstructionasutilizedbytheb-galgorithmforcaseswithmultiplicity1.(a)Multiplicity1onbothsides.(b)Multiplicity1onasingleside.Onlyonepossibilityexistsforthesecases.intersectionofthefourstrips.Assumingthepixelwiththegreatestamountofdepositedenergywasattheintersectionofthetwostripswiththegreatestamountofenergy,twoscenarioswerepossibleifES1(1)>ES2(1)(forthecaseofES2(1)>ES1(1),S1andS2aresimplyswappedinthefollowingschemes).IfES2(1)ES1(2)>ES1(2)andES2(1)ES1(2)>ES2(2),thearrangementofpixelsisshowninFig.3.40panela.Otherwise(ifES2(1)ES1(2)waslessthantheenergiesofeitherofthetwostripswiththelowestenergy),thearrangementofpixelsisshowninFig.3.40panelb.Thisis,ofcourse,nottheonlypossiblearrangement,thoughit'sinclusioninthealgorithmincreasesthefractionofgraysrecoveredbyabout3%absolute.Thisschemewaschosenbaseduponthemostcommonandleastambiguouspixelarrangementsincetheenergiescouldbecalculatedbaseduponadditionandsubtractionofstrips,notrandomfractionsofstripenergiessplitamong4pixels.Intotal,whensimulatingthedecayof67Fe,thealgorithmrecovered171%ofemittedgraysat189keV,whichisanincreaseovertheamountrecoveredbyastriphistogram(10%)inthepresenceofelectrons.61Figure3.39Anillustrationofthestriparrangementsandpixelreconstructionasutilizedbytheb-galgorithmforcaseswhereonesidehasmultiplicity2.(a)Multiplicity2onbothsides.(b)Multiplicity2onasingleside.Multiplearrangementsarepossible.3.6.2ApplicationoftechniqueindataInordertoidentifythedecaysofthe67Coions,severalhigh-energyg-raytransitionsthatpopulatethe680.5-keVstateemittingthe188.9-keVgraywererequiredtobeobservedinSeGA.ThesetransitionsareshowninFig.3.41.Aftergatingonthehighenergyfeedingtransitions,thestriphistogram(aplotoftheenergiesdepositedinallstripsintheGeDSSD,withoutanyb-gsummingalgorithmsapplied)forbothsidesoftheGeDSSDareshowninFig.3.41and3.42.Thesimulationpredictedthatthestriphistogramwouldhaveanefyof101%.BaseduponthetotalnumberofcountsofthegatedSeGAgraysandtheknownabsoluteef287countswouldbeexpectedwithintheGeDSSDstriphistograms.Theexperimentalspectrawereconsistent,withinerror,ofthisvalue.Afterapplyingtheb-gsummingcorrectionalgorithmontheexperimentaldata,therewasanincreaseincountsinthe188.9-keVpeak.Thesimulationpredictedthat171%oftheemittedg62Figure3.40Anillustrationofthestripandenergyarrangementsfortwocaseswheretheenergywithinthestripsissplitbetweenmultiplepixels.(a)IfES2(1)ES1(2)>ES1(2)andES2(1)ES1(2)>ES2(2),thisarrangementputsthemaximumenergyattheintersectionofthestripswiththehighestenergy.(b)Otherwise,ifES2(1)ES1(2)wouldnotresultinthehighestpixelenergy,thisalternatearrangementpreservesthemaximumpixellocation.Figure3.41SeGAenergyspectrumshowingthehigherenergygraysat2088.7,2079.8,and2054.2keVusedasgatestoselectthe188.9keVtransitionusedfortestingtheb-gsummingalgorithm.63Figure3.42StripenergyspectrumofthebacksideoftheGeDSSDaftergatingonthegraysshowninFig.3.41.Thenumberofcountsinthepeakat189keVisconsistentwiththe10%predictedbysimulation.Figure3.43StripenergyspectrumofthefrontsideoftheGeDSSDaftergatingonthegraysshowninFig.3.41.Thenumberofcountsinthepeakat189keVisconsistentwiththe10%predictedbysimulation.64rayswouldbeobserved,leadingtoanexpectationof4813countsat189keV.Theexperimentalg-rayenergyspectrumafterapplyingtheb-gsummingalgorithmisshowninFig.3.44,wherethepeakhas3211counts,whichagreeswiththelowerpredictedrangeofthealgorithm.Figure3.44EnergyspectrumintheGeDSSDfromtheb-gsummingalgorithmtore-createthepixelenergiesgatedonthethreehighenergytransitions,2055,2080,2088in67Fe.Theintensityofthe189-keVtransitionisshown.3.7Double-pulseprocessingThedepositionofenergywithintheGeDSSDcreatesavoltagesignalfromthewithasharprisefromabaselinevoltage,risingtoamaximumandthendecayingwithacharacteristicdecaytimebacktowardthebaseline.However,somepulsesdeviatingfromthischaracteristicshapecanbefoundinthedata.Whilesomealternateshapesarenotunderstoodandcanbeoutbypulseprocessing,thosepulsesthatlooklikeastair-steparetwopulsesinonetraceseparatedbyanamountoftimelessthanthetracelength(Fig.3.45).Atraceofthistypecorrespondstotwoenergydepositionsverycloseintimewithinasinglestrip,suchasthepopulationandsubsequentdecayofshort-livedisomericstates.Thus,boththetimingbetweenthetwopulsesand65theamplitude(energy)ofanypulsewiththisshapecanbeextracted.Thetechniquedescribedinthisworktoanalyzedouble-pulseswasadaptedfromworkinRef.[67,68].Toidentifythesedouble-pulses,anidealpulse-shapedatabaseforeachchannelintheGeDSSDwasgeneratedbaseduponaveragingthetraceshapeforeachstripforthe662-keVgrayfroma137Cssource.Aminimumof1000baselinesubtractedtraceswereaveragedforeachstrip.Thetriggeroftherisewithinthetraceswasfoundandalignedsothatalltracestriggeredatthesamepointwithinthetrace(andthusalignedtherisesofthetraces).Traceswithleadingedgesbeforethecommonstartpoint(hereat500clockticksor4ms)weredelayed,andtracestriggeringafterthecommonstartpointwereadvancedsothattheleadingedgesofalltracesstartedat500clockticks.Thetotallengthofatraceis2500clockticks,or20ms.First,thetracewasattemptedwithasingle-pulse-shape.Theformofthewas:Fit[i]=B+S(IdealPulse[i+P])(3.11)whereFit[i]isthevalueoftheinADCunits,Bisathevalueofthebaseline,Sisascalingfactor,andIdealPulse[i+P]isthepulseheightinADCunitsatbiniasdeterminedbytheidealshapeofthatstripincludingatimingoffsetP.Theidealpulsewasscaledtomatchtheheightofthetrace,whichalsogivestheenergy.Atracewastbetweenbins200and2300,encompassingaportionofthebaseline,therise,andaportionthedecaybacktowardbaselinewithinthetracelength.Thebaselinewasdeterminedbyaveragingthevalueoftracebetween10and300clockticks,andwaskeptconstantinthewhilethescalingfactorandtimingoffsetparameterswereallowedtovaryfreely.Thechi-squareofthewasasfollows:c2=2300åi=200(Trace[i]Fit[i])2(3.12)whereTrace[i]andFit[i]arethevaluesofthetraceandtheofthepulseatindexiinADCunits.TheerrorintheTrace[i]andFit[i]areassumedtobe1.Thelogarithmofthechi-squaredividedbytheamplitudeofthetraceisshowninFig.3.46forthefrontandFig.3.47fortheback.Thevalueofthechi-squarewassystematicallyhigherfor66signalswithlargeramplitudes,sothechi-squarewasdividedbytheheightofthetracetoaccountforthiseffect.Thelogarithmofthenormalizedchi-squarevaluesmadetheofmeriteasiertovisualize.Thisvaluewascomparedtoselectedcutoffsinordertoidentifywhetheratraceisasingle-pulse.Forthefront,thevalueselectedasacutoffwas3.15,whileforthebackthisvaluewas3.05.Thesevalueswerechosentominimizethenumberofsingletracesatthetailendofthedistributionbeinglabeledadoubletrace,andtomaximizethenumberofdoubletraceswithshorttimingdifferences.Ifthesinglechi-squarecutoffwastoolow(forexample,2.9onthebacksideoftheGeDSSD),traceswithaslowrisetimeliketheoneshowninFig.3.48failthesingle-pulsetest,andaresubsequentlylabeledadouble-pulse.Likewise,ifthesingle-pulsechi-squarewastoohigh,someofthedouble-pulseswithshorttimingdifferencespassedthesingle-pulsechi-squarecutoff,andthusdidnotgetlabeledasadouble-pulse.Fig.3.49showsadouble-pulsethatpassedthesingle-pulsetestwhenthechi-squarevaluewas3.2.Thevalueofthesinglechi-squarewaschosentobalancebetweenthesetwoeffects.Nearthecutoff,bothsingletraceswithaslowrisetimeanddouble-pulseswithashorttimingdifferencebetweenthetwopulsesexhibitsimilarchi-squarevalues.Figure3.45Anexampletraceexhibitingthedouble-pulse-shapesearchedforbythistechnique.67Figure3.46Thelogofthechi-squaredistributionofthesingle-pulseovertheamplitudeofthepulseforthefrontstripsofthedetector.Acutoffof3.15(shownasthereddashedline)forthefrontstripswasusedtodeterminewhetherthewasgood.Figure3.47Thelogofthechi-squaredistributionofthesingle-pulseovertheamplitudeofthepulseforthebackstripsofthedetector.Acutoffof3.05(shownasthereddashedline)forthebackstripswasusedtodeterminewhetherthewasgood.68Figure3.48Anexampletraceonthebacksideofthedetectorincorrectlylabeledasadoubletraceifthecutoffisloweredto2.9.Theinsetshowsacloserviewoftherisetoillustratethedouble-pulseThetraceisshowninbluewhiletheisshowninred.Figure3.49AnexampletraceonthebacksideoftheGeDSSDincorrectlylabeledasasingle-pulsewhenthecutoffwasraisedto3.2.Thistracethatclearlyhastwopartsandshouldbeasadouble-pulse.69Ifthesingle-pulsetestwasfailed,thenaofacombinationoftwosingle-pulsesoffsetintime(adouble-pulse)wasattempted.Theformforadouble-pulsewasthesumoftwosingleidealpulses,offsetintime:Fit[i]=B+2åk=1Sk(IdealPulsek[i+Pk](3.13)whereBisthebaseline,Skarethescalingfactors,Pkarethetimingoffsetsofthetwopulses,andthesumisoverksingle-pulses.Eachpulsewasindividuallyscaledfortheheightofthetrace,andwasforatimingoffset(relativeto500clockticks).Ifthedoublewasgood,thenthateventwasasadouble-pulseevent.Forallpulsesforwhichadoublewasattempted,thechi-squareresults(calculatedinthesamewayasforthesingleareshowninFig.3.50forthefrontofthedetectorandFig.3.51fortheback.Acutoffof2.95wasutilizedforthefrontstrips,andacutoffof2.85waschosenforthebacktoidentifydouble-pulses.Aswiththesinglethechi-squarevalueswerechosentomaximizethenumberofdouble-pulsespassing,andminimizingthenumberofotherpulse-shapespassing.Inthefrontstrips,comparetothebackstrips,therewasalargernumberofunusuallyshapedtraces.Thesetracesfailedthesingle-pulsetest,butmanywereabletopassthedouble-pulsetestwithchi-squarevaluessimilartothoseoftruedouble-pulses.Forthesereasons,thedistributionsinthedouble-pulsechi-squarearedifferent.Anexampleofadouble-pulseisshowninFig.3.52.Inordertoensurethatthevaluesoftheparametersremainphysical,alimitof30clocktickswasplacedonthetimingdifferencebetweenpulses,andbothpulsesmusthaveapositiveenergy.Atiminglimitshorterthan30clockticksallowedmoresingle-pulses,aswellaspulseswithatransientsignalontherise,topassthedouble-pulserequirements.Withthelengthofthetraceandtheminimumpulseseparation,thehalf-livesthatmaybestudiedbythistechniquewerelimitedbetween240nsand20ms.Ifneithermatchedthetracewell,thenthetracewasmostlikelynoisyorotherwisepoorly-shapedtrace,andisthusnotincludedinthesingleordouble-pulseresults.Outofallevents,onlyaverysmallpercentage,0.04%,weredouble-pulseswithacceptableparameters.ResultsfromthistechniquewillbediscussedinSections5.3.1and5.3.2.70Figure3.50Thelogofthechi-squaredistributionofthedouble-pulseovertheamplitudeofthepulseforthefrontstripsofthedetectorthatfailedthesingleAcutoffof2.95forthefrontstripswasusedtodeterminewhetherthewasgoodandthereforecouldbeconsideredadouble-pulse.Figure3.51Thelogofthechi-squaredistributionofthedouble-pulseovertheamplitudeofthepulseforthebackstripsofthedetectorthatfailedthesingleAcutoffof2.85forthebackstripswasusedtodeterminewhetherthewasgoodandthereforecouldbeconsideredadouble-pulse.71Figure3.52Anexampledouble-pulse(blue)withthefunction(red).72CHAPTER4EXPERIMENTALSETUP4.1IntroductionFortheremainderofthisdocument,resultsfromaNSCLexperimentfocusedonpopulatingA˘110nucleiwithZbetween40and46willbediscussed.Nucleiinthisregionhavelongbeenofinterestduetotherapidlychangingstructurewithintheregion[25,27,69Œ71].Anexampleofanisotopicchain(Ru)exhibitingthesestructuralchangeswasdiscussedinSection1.2.2.Inparticular,experimente11003focusedonproducingNb,Mo,Tc,andRuisotopestosearchforisomericstatesinMo,Tc,Ru,andRhdaughternuclei.Thischapterpresentdetailsofthedetectorandbeamsusedfortheexperiment.Theexperimentalsetupfore11003wasverysimilartothecommissioningrunsetups.IonsweretransmittedthroughtwoPINdetectors,aKaptonwindow,afewcmofairandthencametorestinsidetheGeDSSD.TheGeDSSDwasdiscussedindetailinChapter3.SurroundingtheGeDSSDwere9HPGecloverdetectors[51],whichwillbediscussedingreaterdetailinSection4.44.2BeamsettingsForneutronrichnucleiwithA˘110,theLISEcode[59]predictslowproductionrates,withsomenucleiexpectedtobeproducedwithonly500ionsoverthecourseof10days.ThreerigiditysettingsoftheA1900fragmentseparator[41]wereusedtodeterminetheproductionsettingandarelistedinTable4.1.Ateachsetting,thePID(particlewasusingb-delayedgraysfromknownisotopesthatwereimplantedintheGeDSSDbeforemovingtothenextsetting.Theprimarybeamwas124Snatanenergyof120MeV/uforallthesecondarybeamsettings,andwasimpingedona9Betarget,thethicknessofwhichdependeduponthebeamsetting(seeTable4.1).ThesecondhalfoftheA1900waskeptataconstantrigidityof3.931Tm73tosimplifyparticleaswastheKaptonwedge,atathicknessof20mg/cm2.Theprimary124Snbeamwasdeliveredtotheend-stationintwochargestates,fully-stripped124Sn50+andHydrogen-like(H-like)124Sn49+tocalibratethelow-gainstripsintheGeDSSDandPINdetectorsforaTotalKineticEnergy(TKE)measurement.Theenergiesofthe124SnbeamsaresummarizedinTable4.2.BothSnbeamswererunatthestartoftheexperiment,withthefully-strippedrunfor60minutesandtheH-likefor15minutes.Thefully-strippedbeamwasrunagainattheendofthebeamtimeforanadditional90minutes.ThehalfoftheA1900hadarigiditysettingforthefully-strippedandH-likebeamsof3.931Tmand3.962Tm,respectively.Table4.1Summaryofthethreebeamsettingusedintheexperiment.CentralBrFirstBrSecondTargetMomentumWedgeIsotopeHalf(Tm)Half(Tm)Thickness(mg/cm2)Acceptance(%)Thickness(mg/cm2)118Ag4.0333.93190.520117Ru4.0393.9311411.520112Nb4.0383.931188520Table4.2ThepredictedenergydepositionfromLISEwithinthePINsandGeDSSDforthetwoSnbeamsine11003.BeamDetectorEnergy(MeV)124Sn50+GeDSSD6854PIN11486PIN21522124Sn49+GeDSSD6056PIN1977PIN21007TheA1900settingwascenteredon118Agwitha0.5%momentumacceptanceanda9mg/cm2Beproductiontarget.ThisbeamwascharacterizedbytheA1900groupandthePIDwasbydecays.Thesettingranforapproximately9hours.Thesecondsettingwascenteredon117Ruwitha1.5%A1900momentumacceptanceanda141mg/cm2Beproduction74target.ThissettingwaschosenasanintermediaterigiditytocheckthescalingoftheA1900separator.Thesecondsettingranforapproximately18hoursandthePIDwasagainbasedontheb-gcoincidences(discussedinSection5.4.1).TheA1900settingfor112Nbutilizedthefull5%momentumacceptanceoftheA1900anda188mg/cm2Beproductiontarget.The112Nbsecondarybeamranfortheremainderofthebeamtimeofapproximately98hoursandthePIDwasbasedontheb-gcoincidences(seeSection5.4.2).4.3ParticleMultipleisotopesweredeliveredtotheexperimentalend-stationinaso-calledcocktailbeam,andevent-by-eventisotopewasperformedwithDEandTOFmeasurements.TwoPINdetectorsofthicknesses488and303mmwereplacedapproximately1mupstreamoftheGeDSSDinvacuum.Withthe124Sn50+beam,thePINresolutionsat1486MeVforPIN1(448mm)was2.3%andat1522MeVforPIN2(303mm)was2.2%.Asparticlespassthroughamaterial,theparticlesloseenergyinproportiontoZ2.TheenergydepositedintoPIN1fortheRubeamsettingispresentedinFig.4.1andseveralpeaksareapparentcorrespondingtotheelementsdeliveredduringtheexperiment.TherelationshipbetweenenergylossandtheZofaheavychargedparticlecanbeexpressedthroughtheBetheformula[65]:dEdx=4pe4z2m0v2NZ"ln2m0v2Iln 1v2c2!v2c2#(4.1)wheredEdxisthedifferentialenergylossforaparticlewithinamedium,visthevelocityoftheparticle,zistheatomicnumberoftheparticle,Nisthenumberdensityofthematerial,Zistheatomicnumberofthematerial,Iistheaverageexcitationandionizationpotentialoftheabsorber,m0istheelectronrestmass,cisthespeedoflight,andeisthechargeoftheelectron.OnemethodforidentifyingthemassnumberoftheproducedionsisaTOFmeasurement.TheA1900selectsionswiththesamemomentumtochargeratio:mvq.Withalltheionsproducedatroughlythesamevelocity,theTOFisproportionatetoaparticle'smasstochargeratioifall75Figure4.1PIN1energies(DEsignals)fortheRubeamsetting.Thedifferentelementsaremarkedontheparticleshavethesametotalpathlength.TheTOFwasmeasuredbetweenPIN1atthefrontofthesetupandthescintillatorattheintermediatedispersiveimage2(I2)positionintheA1900.ThePINtimingwasusedasastartsignalandthetimingfromtheI2scintillatoratthecenteroftheA1900wasdelayedandusedasastopsignal.Inthisway,ionsthatdidnotmakeitfromtheacceleratortotheexperimentalend-stationdidnotproducestartsignalswithoutsubsequentstopsignalsinthedataacquisition.Athighmomentumacceptancesandheaviermasses,twoadditionalfactorscomplicatetheDEandTOFtechniques:variationsinionpathlengthandchargestateambiguities.4.3.1Image2TOFcorrectionThefactorcomplicatingionisthattheTOFdependsupontheion'stotalpathlengththroughtheA1900.Particlescantakeslightlydifferentpathsthroughtheseparatorduetotheirmomentum.Thisresultsindifferenttotaltraveldistancesthroughtheseparator,blurringtheTOF,andrequiringcorrectionsothattheTOFoftheionsisindependentoftheirpath.ThemomentumofaparticleiscorrelatedwithitspositionatImage2oftheA1900andtheTOFcanbe76correctedwithapositionmeasurement.ThiseffectisillustratedinFig.4.2,wherethecorrelatedpositionatI2withtherawTOFisvisiblein(a)andthenon-correctedpoorparticleinwhichtheindividualisotopesareunresolvedisvisiblein(b).TheTOFwascorrectedtobeindependentoftheion'spositionintheI2scintillatorandtheresultingcorrectedTOFandPIDareshowninFig.4.3.4.3.2TotalkineticenergyThesecondfactorcomplicatingionistheproductionofmultiplechargestatesofthesameisotopeleadingtoambiguitiesinthePIDbecausemultipleisotopesofagivenZcanhaveverysimilarmasstochargeratios.Theexperimentwasfoundtohavedeliveredfully-stripped,H-like(oneelectronremaining),andHe-like(tworemainingelectrons)secondaryionstotheexperimentalend-station.Forexample,118Rh45+hasamasstochargeratioof2.62,115Rh44+hasamasstochargeratioof2.61,and119Rh45+hasamasstochargeratioof2.64.Therefore,inthepresentexperiment,adjacentmassesinanisotopicchainwiththesamechargestatewillappearasdistinctgroupsnaPIDplotbutwillbecontaminatedwiththe(A-3)massnucleusinalowerchargestate.ThisdifisdepictedbythecartooninFig.4.4.TheexperimentalPIDcanbeseeninFig.4.5;thegroupmarkedwithablackcirclecontainsboth118Rh45+and113Rh44+.OnemethodtoseparatedifferentchargestatesistomeasuretheTKEoftheionssincetheTKEisproportionaltothemassoftheion.Inanidealexperiment,theTKEcanbereconstructedfromtheenergydepositedintoallofthedetectors.Inthepresentsystem,thiswasnotpossibleduetotheGeDSSDcryostat.Inexperimente11003,theionspassedthroughthePINdetectors,aKaptonwindow,asmallamountofair,theGeDSSD'sAlcryostat,andarestoppedintheGeDSSD,depositingallremainingenergy.ThisisillustratedinthecartooninFig.4.6.SincetheI2scintillatorprovidesameasureofthemomentum,plottingthesumofenergiesinthePINdetectorsandtheGeDSSDversusthepositionwithintheI2scintillatorshouldshowacorrelationandawaytoseparatemultiplechargestates.AccordingtoLISEcalculations,theTKEfortheionsproducedinexperimente11003wasexpectedvarybetween4and11%,dependingontheion.For77Figure4.2(a)TOF(arbitraryunits)vs.Image2positionforallparticlesillustratingtheneedtocorrectTOF.(b)ThePIDplotfortheRusettingwithnon-correctedTOF(arbitraryunits).Theisotopesoverlapinthisalthoughtheelementsareseparated.78Figure4.3(a)ThecorrectedTOF(arbitraryunits)andImage2positionforallparticlesillustratingthesameTOFforallpositionswithintheI2scintillator.(b)ThePIDplotfortheRusettingwiththecorrectedTOF(arbitraryunits).79Figure4.4Cartoondepictingtheproblemcreatedbythecreationofmultiplechargestates.EachchargestateformsaPID.ThesePIDoverlap,creatinggatesthatincludemultiplenuclei.ThechargestatesshownmatchwhatwasobservedintheRusecondarybeamsetting.Figure4.5PIDfortheRusetting.Thespotmarkedcontains115/118Rh,whichwasusedtoinvesti-gateTKEmeasurementstoseparatedifferentchargestates.80the115/118Rhexample,theexpectedseparationis4.9%.Thecalibrationovertimeforthefrontlow-gainstripsshiftedontheorderof2%,sothegainmatchingasafunctionoftime(discussedinSection3.3.3.2)wasimportanttoobtainagoodTKEmeasurement.ThesumoftheenergydepositedinthePINsandthelow-gainstripsofGeDSSDwasusedtoapproximatetheTKE(astherewereadditionalmaterialsthebeampassedthroughonitswaytothesensitivevolumesofthedetectors,losingmoreenergythatwasnotdetected).ThepositionattheI2scintillatorisplottedvs.theTKEinFig.4.7withtheexpectedlocationsof115Rhand118Rhindicated.Theisconstrainedtoeventswithintheedgestripsofthedetector.Themiddleofthedetectorwasmoreradiationdamaged(seeSection3.3.3.2),andclearseparationwasnotachieved.Forcomparison,theI2positionvs.TKEisdisplayedforionsthatstruckthemiddleofthedetectorinFig.4.8,wherethemiddleofthedetectorisasstripsnumbered7to12,inclusively.Figure4.6Cartoondepictingthedepositionofenergyasionsmovethroughtheexperimentalsetup.Asanexample,theenergydepositioninthePINdetectorsoftheproducedRhisotopesarenoted.Theb-delayedg-rayspectrumobservedwithin500msofthearrivalofa115Rh44+or118Rh45+ionisshowninFig.4.9.Previouslyknowngraysfrombothisotopes[72Œ74]canbeobservedandarelabeledwiththeirrespectiveenergies.ThesamespectrumobtainedwiththeedgestripsoftheGeDSSDisshowninFig.4.10,andthesametransitionswereobserved.Figs.4.11and4.12illustratetheseparationofthetwochargestatesbycomparingtheb-delayedcloverspectrafrom81Figure4.7TheTKEvs.thepositionoftheionswithintheImage2Scintillatorthatdemonstratetheseparationofchargestates.Thisshowseventsonlyfortheedgestripsinthedetector.Figure4.8TheTKEvs.thepositionoftheionswithintheImage2Scintillatorthatdemonstratethelackofseparationofchargestatesshownonlyforthemiddlestripsinthedetector.82thetwogatesshowninFig.4.7.ThetotalnumberofcountsineachTKEgatefromFig.4.7isgivenforreferenceinTable4.3.Theobservednumberofcountsat126keVand378keVarecomparedtotheexpectednumberofcountsiftherewasnoTKEseparation(i.e.scalingthepeaksinFig.4.10bythepercentageofionsineachTKEgateinFig.4.7).Thepeaksinthe118Rhgateclearlydonothavealinearscalingwiththetotalcountswithinthegates,whilethoseforthe115Rharemuchclosertothevaluesexpectedbyscaling.Figure4.9b-delayedg-rayspectrumcorrelatedwith115/118Rh.Previously118Rhgrays[72,73]arelabeledinredandpreviously115Rhgrays[74]arelabeledinblack.Thepeakat126keV(115Rh)isthesumoftwoverycloseinenergypeaksat125and127keV(both115Rh),andthecorrelationtimewas500ms.ThereareseveraladditionalwaystheTKEmeasurementandthePIDcouldbeimproved.Betterenergyresolution(lowerradiationdamage)wouldhelpincreaseseparationbetweenchargestates.Secondly,lessinterveningmaterialwouldalsohelptheTKEmeasurement.Withlessmaterialtopassthrough,theresultingwidthoftheTKEdepositedintheGeDSSDwouldbereducedastheresultofdecreasedenergystraggling.OnewaytoaccomplishthiswouldbethroughthecreationofaGeDSSDthatcanbeattacheddirectlytothebeamlinevacuum,eliminatingtheAlentrancewindow,Kaptonwindowandairthroughwhichtheionsmusttravel.83Figure4.10b-delayedg-rayspectrumcorrelatedwith115/118Rhandtotheedgestrips.grayspopulatedbythedecayof118Rh[72,73]arelabeledinredandgraysfrom115Rh[74]arelabeledinblack.Thepeakat126keV(115Rh)isthesumoftwoverycloseinenergypeaksat125and127keV(both115Rh),andthecorrelationtimewas500ms.Figure4.11b-delayedg-rayspectrumcorrelatedwith118Rhandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof118RhwasappliedtotheSeetextfordetails.84Figure4.12b-delayedg-rayspectrumcorrelatedwith115Rhandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof115RhwasappliedtotheSeetextfordetails.Table4.3Observedcountsfortransitionsin115Rhand118RhdecayscomparedtotheexpectednumberofcountsiftherewerenoTKEseparation.Theexpectednumberofcountsweredeter-minedbyscalingthenumberofcountsofeachgraybythetotalnumberofimplantsforthenumberwithineachgate.NumberofScaledNumberofScaledGateTotalinObserved126126keVObserved378378keVTKEGatekeVCountsCountskeVCountsCountsAllEdgeEvents41505223-3413-115Rh(left)173520142210136145118Rh(right)134562177208114854.4GecalibrationThecalibrationandefysimulationsoftheGeDSSDwerediscussedinSection3.3forboththelow-gainandhigh-gainstripsinthedetector,andthecalibrationandefyofthecloverdetectorsusedinexperimente11003willbediscussedinthissection.FourcloverswereplacedupstreamoftheGeDSSDinacross,fourplaceddownstreaminasecondcrosswiththeninthdetectorplacedatzerodegreesdownstreamoftheGeDSSDinsidethesquareformedbythefourotherdownstreamclovers.AphotographofthesetupisshowninFig.4.13.Theupstreamarraywasnumbered1-4,whereclover1waslocated(facingupstream)atthe1o'clockpositionwithnumberingincreasingclockwiseuptoclover4atthe11o'clockposition.Inthedownstreamring(stillfacingupstream),clovers5-8werenumberedsimilarly,startingwithclover5inthe1o'clockpositionandincreasinginnumberingclockwisetoclover8.Clover9wasatthebackofthearray,inthecenterofthedownstreamgroup.Thereweretwocryostatdesignsamongtheninecloverdetectors.Clovers1-5and8-9hadonecryostatdesignandclover9wasusedasatypicalexample.Clovers6and7wereofaslightlydifferentcryostatdesign,andclover7wasusedasatypicalexample.TheninecloverdetectorsoriginatedfromtheYRASTBallarray,formoreinformationaboutthedetectorspleaseseeRef.[75].4.4.1calibrationTheefyofthecloverscannotbemeasuredusingasourceattheionimplantationlocationwithintheGeDSSD.Therefore,datafromaSRMsource(herea154/155Eusource,SRM4275C-69.)wastakenatseveralpositionsaroundthearrayasawhole,aswellasnearclovers7and9individually.Themeasuredefweresimulatedandthesimulationwasmatchedtothedata.Additionally,theeffectsofsummingcorrectionsweretakenintoaccountwiththecloverefycalibrations.Thesecorrectionsaccountforanyinterferenceinmeasuredcountingratesduetothepresenceofothertransitions,andareafactortodividethemeasuredefy.ThesecorrectionsaretabulatedbelowinTable4.4andaretypicallybetween0.8(aswasthecasewith86Figure4.13AphotographoftheexperimentalsetupwiththedownstreamsetofcloverspulledbacktoshowtheGeDSSDinfrontoftheupstreamcross.Beamexitsthepagetowardtheviewer.TheninthdetectorisplacedirectlybehindtheGeDSSDatthecenterofthecross.sourcepositionsonthesidesofclover9)and1.TheSRMsourcewasplacedonthefrontfaceandonthesideofclovers7and9fordetailedcomparisionstoGeant4simulations.ThecomparisonbetweensimulationandexperimentwhenplacingthesourceonthefrontfaceofthedetectorsispresentedinFig.4.14.Thesimulationwasslightlylowatenergiesbelow200keVandthiswaslikelyduetomoreabsorbingmaterialpresentthatisnotinthedetectors.However,removingsomematerialworsensthematchathigherenergies,sothesimulatedcryostatthicknesswaschosentobalancethemiss-matchbetweenlowandhighenergies.Similarly,thematchbetweensimulationandexperimentforasourceplacedonthesideofthecryostattwoinchesfromthefrontfaceofthedetectorisshowninFig.4.15andFig4.16forclover9and7,respectively.Theseshowareasonableagreementbetweensimulationandexperimentathighenergieswhichgraduallygetsworseatlowerenergies.Therestofthearraywasalsosimulatedwiththesourcepositioninfrontofclover9(Fig.4.17)(a).Sincetherearesomedeviationsbetweentheexperimentandthesimulation,anestimateof87Figure4.14Thecomparisonbetweenexperimentallydetermined(blackcircles)andsimulatedef(redsquares)from0-1650keVforasourceplacedonthefrontfaceof(a)clover7and(b)clover9.Theefyforeachcrystalwithinthecloverdetectorwasdeterminedindividually,andthentheeffromallfourcrystalsweresummedtogivetheefyinthe88Figure4.15Thecomparisonbetweenexperimentallymeasured(blackcircles)andsimulatedef-(redsquares)forasourceplacedonthesideofclover9for(a)acrystalclosesttothesourceand(b)acrystalontheoppositesideofthedetectorfromthesource.89Figure4.16Thecomparisonbetweenexperimentallydetermined(blackcircles)andsimulationedef(redsquares)forasourceplacedonthesideofclover7for(a)acrystalclosesttothesourceand(b)acrystalontheoppositesideofthedetectorfromthesource.90Figure4.17(a)Thecomparisonbetweenexperimentallydetermined(blackcircles)andsimulatedef(redsquares)forasourceonthefaceofclover9.Theefshownareforthesumofthedownstreamcloverringusingtheerrorastheuncertainty.(b)Thesameplotas(a),includingthedegreeofmiss-matchbetweensimulationandcloverwithintheuncertainty.Seetextfordetails.Theefyforeachcrystalwithinthedetectorswasdeterminedindividually,andthentheefofallcrystalswereaddedtogethertogivetheefyshowninthe91Table4.4Tableofg-rayefysummingcorrectionsfortheSRMsource.[E]denotesthetotalefyat"E"keV(calculatedfromsimulation),whilefEgisthepeakefyat"E"keV.Measuredefaredividedbythesummingcorrectiontoaccountforthecorrection.Energy(keV)SummingCorrection42.81.086.61.0105.31.0123.11.0-0.072[248.0]-0.055[591.7]-0.120[723.3]-0.130[873.2]-0.20[1004.8]-0.401[1274.4]-0.02[1596.5]247.71.0-0.287[42.8]-0.455[123.1]-0.134[591.7]-0.039[723.3]591.81.0-0.297[42.8]-0.455[123.1]-0.178[248.0]-0.800[1004.8]723.31.0-0.154[42.8]-0.243[123.1]-0.013[248.0]-0.518[873.2]-0.465[996.4]873.2(1.0-0.282[42.8]-0.455[123.1]-0.894[723.3]996.3(1.0+0.507f123.18gf73.2g/f996.4g)(1.0-0.894[723.3])1004.71.0-0.282[42.8]-0.455[123.1]-0.217[591.7]1274.51.0-0.281[42.8]-0.455[123.1]1596.4(1.0+5.568f873.2gf723.3g/f1596.5g+2.094f1004.8gf591.7g/f1596.5g)(1.0-0.281[42.8]-0.455[123.1])theerrorwasmadeandaddedtotheerrorfromtheofthesimulationoftheimplantationloca-tion.Forallsourcepositions,theefyfromsimulationandexperimentweresummedforallcrystalsandtherelativedifferenceDwascalculated:D=ess(4.2)whereeistheexperimentalefyandsisthesimulatedvalueataparticularenergy.Foreachenergy,thelargestdisagreementbetweensimulationandexperimentfromthe5positionswasselected,andthesevalueswereusedtoobtainanequationforthelevelofdisagreementbetweensimulationandexperimentasafunctionofenergy.Onlythepositioninfrontofclover9hadnoenergieswiththegreatestmiss-match.Thelogoftheaverageerrorwasplottedagainstthelogoftheenergy,andathirdorderpolynomialwastothedata.Thus,theexpectedmiss-matchbetweenexperimentandsimulationmaybecalculatedfromtherelationshipdeterminedbythelog(Err)=0:8474log(E)3+7:0819log(E)219:036log(E)+15:554(4.3)92whereErristheexpectederror,Eistheenergyofinterestandtheconstantsweredeterminedbythethisequation.Fig.4.17(b)showsthecomparisonbetweensimulationandexperimentwiththeadditionalerrorfromthemiss-matchbetweensimulationandexperimentforthesimulateddownstreamcloverring.Finally,theg-rayefyforasourcelocatedatimplantationdepthwithintheGeDSSDwassimulated.Forexperimente11003,thisdepthwas1mmintotheGeDSSD,andthesimulatedsourcewasasquarethesizeofapixel.Table4.5containstheefyforseveralenergies,theuncertaintyintheandtheexpectederrorbetweensimulationandexperimentfromEq.4.3.TheerrorfromEq.4.3isaddedinquadraturetotheuncertaintyfromtheresultsfromaGaussianofthepeaks.TheefyisshowninFig.4.18,withatothesimulation,andtheboundsoftheuncertaintyofthesimulationareshown.Theefencyofthecloverdetectorsatanimplantationdepthof1mmmayberepresentedwiththefollowingequation:log(Eff)=1:4214log(E)4+15:912log(E)366:456log(E)2+122:04log(E)82:001(4.4)whereEffistheefy,EistheenergyandtheconstantsweredeterminedbytheinFig.4.18.Table4.5Thesimulatedcloverg-RayefiencyatimplantationdepthwithintheGeDSSD.Theefofallindividualcrystalswerecalculated,andthensummedtogetherfortheentirearraytogivetheefyshowninthesecondcolumnofthetable.Energy(keV)Efy(%)FitUncertainty(%)Error(%)TotalUncertainty(%)500.5130.03580.1620.1661006.530.1280.7000.7122009.300.1560.7810.7965005.140.1020.6530.66110003.330.08250.6700.67515002.550.07170.6170.62120002.030.06440.5150.51993Figure4.18Simulatedefwithinthecloverdetectorsfromtheimplantpositionof1mmdeepintotheGeDSSD.Alsoshownisthetothoseefandtheuncertaintyinthesimu-latedef4.4.2EnergycalibrationThearraywascalibratedwithrespecttoenergyapproximatelyeveryhourtomeasureanyshiftingdetectorgainsovertime.Occasionally,thecalibrationwouldshiftwithinanhourforsomeofthedetectors,thosedatawerecalibratedmorefrequentlyforalldetectors.Severalbackgroundandsourcegrayswereusedforthecalibration:212Pb:238.6keV,214Bi:609.3keV,60Co:1173keV,1332keV,40K:1460keV.Aquadraticcalibrationwasused,wherecloverrepresentsthenumberoftheindividualdetectorcrystalbeingcalibrated:E(keV)=square[clover]E(ADCunits)2+slope[clover]E(ADCunits)+intercept[clover](4.5)Typically,thevalueofsquare[clover]wassmall,ontheorderof10-7to10-9.ThequalityofthequadraticcalibrationisdemonstratedbytheresidualsshowninFig.4.19forthevecalibrationenergies.Thedifferencebetweenthemeasuredpeakvalueaftercalibrationandtheexpectedvalueofthegrayisplottedvsdetectornumber.Avalueof0correspondstoanexactmatch.Theincludesdatafromallruns,whereeachrunsegmentwascalibratedindividually,94andthetotalhistogramfromtheentiretimewasattheendforthecalibrationresults.Forallcalibrationenergies,thecalibrationiswithin0.5keVoftheexpectedvalue.Figure4.19Energyresidualsfor5g-raytransitionsusedforcalibration,asafunctionofdetectornumber.Thedataencompassestheentiretyoftheruntime.95CHAPTER5RESULTS5.1IntroductionInthischapter,resultsfromNSCLexperimente11003willbepresentedanddiscussed.First,long-livedisomericstatesanalyzedthroughconversionelectronspectroscopywillbedetailed.Thenextsectionwillfocusontheresultsofthedouble-pulseprocessinganalysisasintroducedinSection3.7,andtheshort-livedisomericstatesfoundasaresultofthatanalysis.Finally,b-delayedgraysfoundinboththeRuandNbbeamsettingswillbepresented.5.2Long-livedisomericstates5.2.1IntroductionLong-lived(millisecond)isomericstatescanbecorrelatedtotheheavyionfromwhichtheyorigi-natedinmuchthesamewayasb-decayelectrons.AnisomerwithanenergylowenoughthattheemittedgraysorconversionelectronswouldnotleavetheGeDSSDwouldappearasapeakintheGeDSSDenergyspectrum.Onesuchexampleis115mRu.Previouswork[5]foundevidenceofanisomericstatewithahalf-lifeof76msandag-raytransitionof61.7keVwasassociatedwith115Ruinsteadofthe115Rhdaughter.Therewerenocoincidenttransitionsobservedwiththisgray.Aconversioncoefka=2.70.6wasdeterminedforthe61.7-keVtransitionbasedupontheobservationoftheRuk-shellX-raysandtheassumptionthatallconversionswereassociatedwiththe61.7-keVtransition;thisindicatedamixedM1andE2characterforthetransition.TheenergiesofRuX-raysaregiveninTable5.1.TheWeisskopfestimatefora61.7-keVtransitionistooshortcomparedtotheknownhalf-lifeandtheauthorsofRef.[5]suggestanunobservedgraydepopulatingtheisomerandfeedingthe61.7-keVlevelin115Ru.Thehalf-lifeoftheisomericstatecouldbeconsistentwithalowenergy96Table5.1EnergiesofRux-rays.Inthetable,ShellfdenotestheshellbythevalenceelectronandShellidenotestheinitialvalenceshell.ValuesarefromRef.[76].ShellfShelliX-rayEnergy(keV)kl219.15l319.28m221.63m321.66m421.83m521.83n222.07n322.07n422.10n522.10l1m22.741m32.763n23.181n33.181l2m12.382m42.683n12.892n42.965l3m12.253m42.554m52.559n42.836n52.838M2transition.Theunobserveduppertransitionwasplacedwithanenergy20keVorlessabovethe61.7-keVtransition,sinceitwasassumedthatallakX-rayswereattributedtothe61.7-keVtransition.The(3/2+)groundstatespinandparityof115RuwaschosenbasedonsystematicsoftheotherRuisotopesandtheb-feedingpatterninto115Rh[12].ThespinandparitiesofthetwoexcitedstateswerechosenbasedontheM2intoanM1/E2sequencealongwithsystematics,tentativelyplacinganunobserved(9/2-)levelbelow82keV.975.2.2Identifying115Ru115RuwasproducedinboththesecondandthirdA1900settings,intwodifferentchargestates(fully-strippedandH-like)ineachsetting.ThePIDsforeachsettingareshowninFig.5.1,wherethespotsexpectedtocontain115Ruaremarked.TheexpectedcontaminantsinthePIDgateswere118Ru44+and112Ru43+.Thiswasedbyinvestigatingtheb-delayedg-rayspectra,andsearchingforknowndaughtertransitions.Thesummedb-delayedg-rayspectrumforallfourhighlightedPIDspotsisshowninFig.5.2.Atransitionat292.5keVisclearlyseen,whichcorrespondstothemostintenseRhdaughtergray[12].5.2.3ConversionelectronspectroscopyThedecayenergyspectrumobservedintheGeDSSDcorrelatedto115Ruimplantedinthesameorneighboringpixelandwithin250msisshowninFig.5.3.Aclearpeakisseenat123.8keVandthispeakappearsinall115Rugatesandnoothers.Fig.5.3alsoshowsascaledbackgroundfromthedecayof113Tc,whichwaschosensinceitwasproducedatahighrateanddoesnotfeedanyknownlong-livedisomericstates,resultinginaspectrumwhichshouldbepredominatelyduetob-decayelectrons.The113Tcspectrumwasscaledby0.626accordingtotheratioofionsdeliveredtotheexperimentalsystem.Therelationshipintimebetweenthearrivalofthe115Ruionattheexperimentalend-station,the123.8-keVsignalintheGeDSSD,andtheb-delayedgrayat292.5keVwasexplored.InFig.5.4(a),theb-delayedcloverspectrumisshownforeventsoccurringafterthethearrivalofa115Ruionandbeforethe123.8-keVsignalintheGeDSSD.Theb-delayedgrayat292.5keVwasnotapparentinthespectrum.InFig.5.4(b),theb-delayedcloverspectrumisshownforeventsoccurringaftera123.8-keVsignalintheGeDSSD,upto1safterthe115Ruimplant.Bothspectracouldbemeasuredforupto1sifasignalat123.8keVoccurredverysoonorveryfarafterthe115Rhimplantationtime.Withsucharangeoftheaccumulationtime,thenumberofcountsofthe115Rhdaughtergraydidnotsimplyscalewiththecountingtime.Sincetherewasnoevidence98Figure5.1PIDfor(a)Rusettingand(b)Nbsetting.ThelocationsinthePIDexpectedtocontain115Ruaremarked,alongwiththeirexpectedchargestates.99Figure5.2b-delayedgrayenergyspectrumforalleventscorrelatedtothedecayof115Ruwithin250msinbothA1900settings.Thestrong292.5-keVtransitionassociatedwiththebdecayof115Ruisclearlyseen.Figure5.3GeDSSDmaximumstripenergyspectrumfollowingtheimplantationof115Ru(black),foracorrelationof9pixels.Forcomparison,ascaledspectrumoftheb-decayelectrondistribution,takenfromthebdecayof113Tc,issuperimposed(red).100oftheb-delayedgrayoccurringbeforethe123.8-keVpeak,thissignalwasassociatedwiththe115Ruparentratherthanwiththe115Rhdaughter,andcouldbethepreviouslyisomericstate.Figure5.4(a)b-delayedg-rayenergyspectrumoccurringaftertheimplantationof115Rubutbeforethe123.8-keVsignalintheGeDSSD.(b)Eventsoccurringafterthe123.8-keVsignalintheGeDSSDupto1safterthe115Ruimplant.Fig.5.5(a)showstheGeDSSDenergyspectrumofdecayeventsoccurringinthesamepixel101asthe115Ruimplant.Withasmallercontributionfromtheb-decayelectron,asecond,smallerpeakat62keVbecameapparent.Fig.5.5(b)showstheGeDSSDenergyspectrumforthe8pixelssurroundingthe115Ruion.DuetohighefyforelectronsandgraysatlowenergiesintheGeDSSD,itwasnotimmediatelyobviousifthepeakat123.8keVisasingletransitionorthesumoftwoseparatetransitionsat61.7and62.1keV.Theefyofdetectinganisolated123.8-keVgrayinitsinitialpixelwas24.20.2%,and20.20.2%fortheneighboringpixels(seeSection3.4).Therefore,ifthe123.8-keVsignalwereduetoanisolatedgraytransition,21524countsshouldhavebeenpresentinFig.5.5(b).Ifthepeakat123.8keVwerefromasingleconversionelectron,Table5.2givesthenumberofgraysthatwouldbeexpectedforvariousmultipolarities.Forthepeaktobeasingleconversionelectron,themultipolaritywouldhavetohaveaconversioncoefgreaterthanthatofanE3transitiontobelargerthanthatofthecurrentdataset,andmostlikelylargerthanE5orM5forthepreviousresultstohaveobservednoneofthecompeting123.8keVgray.Table5.2Numberofexpectedgraystobedetectedifthepeakat123.8keVwereasingleconver-sionelectrontransitiongiventhetotalnumberofobservedcountsanddetectorefy.MultipolarityatotNumberofgRaysE10.07516164M10,1710126E20.603762M21.47430E34.67411M311,4114E441.261M491.740.6E5407.70.1M5775.80.07Morelikely,the123.8-keVpeakcorrespondedtothedetectionofboththepreviouslyobserved61.7-keVtransitionandanew62.1-keVtransitions,thusthepeakat˘62keVwasduetoeventswhereoneofthetransitionsescapeditsinitialpixelintheGeDSSD.graysat62keVinGeare102Figure5.5(a)115RudecayeventsobservedintheGeDSSDwithinthesamepixelasthe115Ruionwithin250ms.(b)115RudecayeventsinanadjacentGeDSSDpixeltotheionwithinthesamecorrelationtimeas(a).103Figure5.6ThedistancelowenergygraystravelinGetohave5%oftheirinitialintensityremain-ing.unlikelytotravelbeyondthepixeloforiginbeforeinteracting,asisdemonstratedbythesimu-latedGeDSSDefy.Forexample,thedistancegraysmusttraveltohave5%oftheirinitialintensityremaining,showninFig.5.6,isgivenbytheexponentialfunction:Range=I0I=0:05=e-mx(5.1)whereI0andIaretheinitialandintensities,xisthethicknessofthematerialandmisthetotallinearabsorptioncoefForGe,themassattenuationcoefm=r,isgivenintablespublishedbyNIST[77].GiventhedensityofGe,5.32g/cm3,thelinearabsorptioncoefasafunctionofenergycanbecalculated.Similarly,conversionelectronsresultingfromtransitionsnear62keVareevenlesslikelytraveloutsideofasinglepixel.Fig.5.7showstherangeofelectronsinGe[78]asafunctionoftheirenergy.Thedecaycurveincoincidencewiththe123.8-keVpeakinFig.5.5(a)isshowninFig.5.8.Thedecaycurvewaswithasingleexponentialandconstantbackgroundresultinginahalf-lifeof85(13)ms,whichwasconsistentwiththeliteraturehalf-lifevalueof76(6)msfortheisomericstatein115Ru[5].Anisomerichalf-lifeonthisorderwouldnotbeexpectedtoappearinspectra104Figure5.7TherangeoflowenergyelectronsinGe.Stripwidthis5mmandthecrystalis1cmthick.createdbythedouble-pulseprocessingtechniqueasthehalf-lifeistoolong(seesections5.3.1and5.3.2).5.2.4InterpretationThepreviousresultsforthe115Ruisomerreportedaground-statewithatentativespinandparityof(3/2+),withexcitedstatesofspinandparityof(5/2+)and(9/2-),withthe(9/2-)atanunknownexcitationenergy.Thepresentresultsplacedtheisomericstatein115Ruat123.8keV,seeFig.5.9.Thisdiscrepancyfromthepreviousresultscanbereconciled.First,twotransitionslessthana1keVapartinenergycanbediftoresolve.Inthepreviouswork,theFWHMofthepeakat61.7keVwasontheorderof1-2keV.Inthepresentexperimenttheresolutionwasabout1.5keVat62keV.Second,iftheuppertransitionishighlyconverted,aswouldbeexpectedforahighmultipolarity,high-Z,low-energytransition,fewgrayswouldbeemitted.Assumingthepreviousspinsandparitieswerecorrect,iftheisomerweretotransitiondirectlytotheground-state,themultipolarityoftheresulting123.8-keVtransitionwouldbeE3.BaseduponWeisskopfestimates(Table5.3[79]),thebranchingratiooftheE3transitionrelativetothe105Figure5.8Decaycurveincoincidencewiththe123.8-keVsignalintheGeDSSDfollowingthedecayof115Ru.Theincludesanexponentialparentdecay(green),andaconstantbackground(blue)resultinginahalf-lifeof85(13)ms.Thetotalisshowninred.Figure5.9Thelevelschemefor115Ruassuggestedbythiswork.106M2transitionwouldbeontheorderof10-5andthereforeunlikelytobeobserved.Thepreviousnon-observation[5]ofagrayat123.8keVwithordersofmagnitudemorestatisticsthanthepresentresultsisinagreementwiththisinterpretation,suggestingthatthispathway(E3singletransitiontothegroundstate)wasunabletocompetewiththeM2transitiontothe61.7keV5/2+stateandsubsequentcascadetotheground-state.Table5.3Multipolaritiesofthetransitionsdiscussedintheanalysisof115Ru.Theconversioncoefinthetablehaveanuncertaintyof1.4%[79].Energy(keV)MultipolarityatotWeisskopflWeisskopfT1=2(ms)61.7M11.2237.41099.410862.1M219.231.21041.4123.8E34.6742.01013.5103Theconversioncoeffora62.1-keVM2transitionis19.23,somostoftheisomericdecaysproceededthroughelectronemission.ThedetectionefyoftheGeDSSDforelectronsofthisenergywas˘100%.SincetheenergiesfromallX-raysregardlessofelectronicshellarelowinenergy,andthereforeunabletotravelfartherthanasinglestrip,X-rayemissionfromdifferentshells(forexamplethekorlshells)wouldallresultinapeaksummingto˘62keV.Thesubsequent61.7-keVgraywouldbedetectedineitherthesameorneighboringpixelsoftheGeDSSD,withasmallamountescapingandpossiblydepositingitsenergyinthecloverdetectors.Ifthe61.7-keVgrayescapedthepixelcontainingthe115Ruion,onlythetransitionwouldbeobserved,leadingtothelowenergypeakobservedintheGeDSSDandpossiblecoincidentgraydetectioninthecloverdetectors.TogetherwiththeconsiderationoftheGeDSSD'sdetectorresponse,theobservedpeakat123.8keVwaslikelynotasingletransition,butthesumoftwotransitionssimilarinenergy,comprisingofthesumoftheenergiesofconversionelectrons,X-rays,andgrays.AnothercompetingprocessistheemissionofAugerelectrons.ForRu,theyieldsforthekandlshellsareapproximately0.82and0.02,respectively[39].Thus,internalconver-sionsfromthek-shellwillresultintheemissionofX-raysthemajorityofthetime,whileinternal107conversionsfromthel-shellwillresultintheemissionofAugerelectronsmostofthetime.How-ever,sincetheselow-energyemissionswilltravelveryshortdistancesintheGeDSSD,theenergiesfromanyemittedAugerelectronswillsumwiththeconversionelectron,againyeildingdetectedenergiesof˘62keV.Giventheconversioncoefdetectoref(fromadistributedsourceinsimula-tion),andthenumberofcountsintheGeDSSD,theexpectednumberofcoincident˘62-keVgraysinthecloverdetectorswascalculated.IntheGeDSSDsinglepixelenergyspectrum(Fig.5.5(a)),therewere25829countsinthepeakat123.8keVand4414countswithinthesmallerpeakat62keV(representingeventswhereonetransitionescapedtheinitialpixel)givingatotalof30232isomericdecays,assumingallcascadesledtocountsinoneofthetwopeaks,whichwasreason-ablegiventhenear100%efyoftheGeDSSDattheseenergies.Tothetotalnumberofescapinggrays(andthuswiththeefyofthecloverdetectors,determinetheexpectednumberofcountsinthecloverspectrum),thefollowingsystemofequationsmaybesolved:1:223=N61:7eN61:7g(5.2)19:23=N62:1eN62:1g(5.3)N62:1e+N62:1g=N61:7e+N61:7g=302(5.4)inwhich302isthetotalnumberofcascades,andNisthenumberofemittedparticlesofaenergyandtype.Eq.5.2,and5.3aretheconversioncoeffromTable5.3.Finally,Eq.5.4statesthatsincethetwotransitionsareinacascade,thetotalnumberofcountsfromeachtransitionshouldbeequal.Solving,onendsN62:1g=15andN61:7g=136.Combinedwiththecloverarrayefyof1.580.71%,262-keVgrayswereexpectedcomparedwiththeexperimentalspectrumshowninFig.5.10.Takingeverythingtogether,thelevelschemeshowninFig.5.9issuggested.IncomparisontothetheWeisskopfestimate,theexperimentalhalf-lifeishinderedbymorethananorderofmagnitude.Fig.5.11comparestheexperimentaldecayconstanttotheWeisskopfestimatefor108Figure5.10Cloverenergyspectrumincoincidencewiththe˘62-keVpeakinthesinglepixelGeDSSDspectrum(Fig.5.5(a).severalM2transitionsintheA˘115region,includingatransitioninstable115Sn,wherethematchisquitegood.Forallothernuclei,theWeisskopfestimateishinderedbyaminimumofoneorderofmagnitude.Figure5.11Theratioofexperimentallyobserved[3,9,80,81](lexp)toWeisskopfestimate(lWeiss)forthedecayconstantsofsomeisomericM2transitionsnearA˘115.109Additionally,withasecond,unobservedg-raytransitioninthepreviouswork,thenumberofkaX-raysassociatedwiththe61.7-keVtransitionwoulddecrease,withsomeofthepreviouslyobservedX-rayscorrespondingtotheunobserved,highlyconverted62.1-keVtransition.Thus,themultipolarityofthe61.7keVshouldbeshiftedfromamixedM1andE2transitionclosertoapureM1transition.Thespinsandparitieswereleftthesamehereasinthepreviouswork.Theuppertransitionhasanupdatedenergy,fromanunknownenergylessthan20keVto62.1keV,andthelowertransition'smultipolaritywasupdatedfromamixedM1andE2transitiontoM1.5.2.5SimulationFinally,thisdecaymaybesimulatedinGeant4toverifythattheaboveassumptionsandinter-pretationscanproduceaspectrumconsistentwiththeobservedsignals.A115Runucleuswithtwolevelsandtwoallowedgrayswithoutsubsequentbdecaywasinputtothesimulationatadepthof1mmintothecrystal.ThesimulatedGeDSSDenergyspectrumiscomparedtothatofexperimentinFig.5.12.Thereseemstobeslightlylessofthesingletransitionnear62keVinthesimulationcomparedtoexperiment,with145counts.Insimulation,therewere28525countswithinthe123.8-keVpeak,whichwasconsistentwithintheuncertaintiesintheexperimentaldata.Additionally,thereappearedtobeasimilarnumberof62-keVtransitionsinthecloverhistogramsaswell(Fig.5.13).Modifyingtheparametersofthesimulatedlevelstoallowthe61.7-keVtran-sitiontohaveE2ormixedM1+E2characterresultedinareductionincountsinthe62-keVpeakintheGeDSSDspectrum.Asimulated61.7-keVE1transitiondidnotresultinanyappreciabledifferenceinthesimulatedspectrum.Thesimulated˘20keVRuk-shellX-rayssumwiththeircorrespondingconversionelectrons,matchingthatseenintheexperimenttocreateonlytwopeakswithintheGeDSSD.Therewasnopeakinsimulationintheneighboringstripsat123.8keV.Furthermore,changingthelevelschemeinthesimulationtoallowforacompeting123.8-keVbranchdidnotintroduceapeakintheneighboringstrips,nordidanyotherchangestothesimulatedlevelschemeintroduceasignalintheneighboringstrips.110Figure5.12Comparisonofthesimulatedstripspectra(red)ofthedecayoftheisomericstatein115Ruandtheexperimentalspectra(blue).Figure5.13Comparisonofthesimulatedspectra(red)ofthedecayoftheisomericstatein115Ruandtheexperimentalspectra(blue)forthecoincidentcloverenergydepositions.1115.2.6ConcludingremarksToconclude,theexperimentaldataandsimulatedresultsbothsupportedtheupdatedlevelschemeshowninFig.5.9.Theuppertransitionhasanenergyof62.1keV,keepingthepreviousM2multipolarity.The61.7-keVtransitionmultipolarityischangedfromanM1/E2mixedtransitionclosertoapureM1transition.Thetransitionfromtheisomeric123.8-keVstateisnotabletocompetewiththeotherdeexcitationpathway,andthustheE3crossovertransitionisnotobserved.5.3Short-livedisomericstatesThedouble-pulseanalysisdiscussedinSection3.7canbecarriedoutonthedatafromboththeRuandNbsettingstosearchforshort-livedisomericstates.Thissectionwilldiscusstheshort-livedisomericstatesfoundinthesetwobeamsettings.ThedatashownwerefromtheanalysisofthebackstripsintheGeDSSDbecausethebackstripshadfewersingle-andnoisy-pulsesmixedinwiththepassingdouble-pulsescomparedtothefrontstrips.5.3.1Double-pulsesinRusettingFig.5.14showstheenergyspectrumofallsignalsasthesecond-pulseinthecharacter-isticdouble-pulse-shape(seeSection3.7).Twopeakswereclearlypresentinthisenergyspectrumat49.33.6and155.74.1keV(Fig.5.14),whiletherewerenoapparentpeaksinthehistogramoftheenergies(Fig.5.15).Veryfewcountsexistedinthesecond-pulsespectrumabove500keV.ThisdidnotappeartobeduetolargeamplitudesofthemostoftheADCrange,constrainingtheenergyrangeforthesecond-pulse.HigherenergypulsesthatwouldsaturatetheADCsimplydonotappeartoexist.Notethatbasedupontheassignedtransitions,therecouldbeuptoa4-keVoffsetinthepeakenergies.Thegrayspectrumobservedinthecloverdetectorsincoincidencewiththe49.3-keVpeakinthesecond-pulseenergiesisshowninFig.5.16.Therewereafewcountsnear124,223,and380keV.In118Ag[83],thereexist125.4and379.7-keVtransitionsincoincidencewiththe45.8-112Figure5.14Energyspectrumofthesecond-pulseofdouble-pulsesignalsintheRuset-ting.Figure5.15Energyspectrumoftheofadouble-pulseintheRusetting.Thespectrumisconsistentwithenergeticb-decayelectrons.Forreference,theQ-valueofthedecaydiscussedinthissection,118Pd,is4100(200)keV[82].113keVstate,witha224.2-keVtransitionelsewhereinthelevelscheme(Fig.5.17).Therefore,onepossibilityforthis49.3-keVpeakwasa45.8-keVtransitionwithahalf-lifeontheorderof0.1msin118Ag[83].However,giventherelativeintensitiesinRef.[83],thenumberofcountsexpectedinthepossiblecoincidenttransitions(125,224,380keV)wouldbeanorderofmagnitudegreater.Figure5.16Clovergrayenergyspectrumincoincidencewiththe49.3-keVpeakinthesecond-pulseenergyspectrum.Iftheassignmentto118Agwascorrect,thepeakshouldappearinthedecay-correlatedenergyspectrumoflowerZ,mass118nuclei.Thepeakat49.3keVwascorrelatedwithPIDpositionscontaining118Rh(granddaughter118Ag)and118Pd(daughter118Ag).Thehalf-lifeof118Rhwas310(30)ms[73],whilethatofthedaughter,118Pd,was1.9(1)s[84].Foracorrelationtimeof2s,theGeDSSDsecond-pulsespectrumfor118Rhand118PdisdisplayedinFig.5.18.The49-keVpeakiscorrelatedwithbothimplantedionswithslightlymoreintensityinthe118Pdcorrelatedspectrum.Thetimebetweentheandsecond-pulseisplottedinFig.5.19.Thehalf-lifecurveappearstobeagrowthanddecaycurve,thoughthereisnoclearpeakintheenergyspectrumtoindicatewhichtransitionsmaybepopulatingtheisomericstate.Agoodtothedecaycurvewasnotobtained.Therewasasmallnumberofcountsinotherimplantgates,butthe114Figure5.17Partiallevelschemeof118Ag.DataaretakenfromRefs.[83,84].numberofcountsinthepeakat49keVwasproportionaltothetotalnumberofimplantswithineachgate,atapercentagebetween0.2%to0.4%ofthetotalnumberofimplants.TheA=118gatescontainednearlytwicethatofallotheriongates.Likewise,thecoincidentg-rayspectrumcanbeviewedincoincidencewiththe155.7-keVtransition(Fig.5.20).Asignalseveralcountshighwasseenat283keVincoincidencewiththesignalintheplanardetector.Acandidateforthistransitionwasalso118Ag,witha151.6-keVisomerictransitionandhalf-lifeontheorderof0.1ms[84]incoincidencewitha283.7-keVtransition.GiventhedetectorefandpreviouslydeterminedrelativeintensitiesinRef.[84],fromthenumberofcountsinthepeakat156keV,164countsat283keVwouldbeexpected,withwashigherthanthe5to6countsat283keVinFig.5.20.AsisdemonstratedinFig.5.18,the156-keVtransitionwasalsocorrelatedwith118Pdimplants.ThetimingdifferencebetweenthetwopulsesisdisplayedinFig.5.21.Thepeakat155keVdidnotexistinanyother115Figure5.18GeDSSDsecond-pulseenergyspectrumgatedon(a)118Rhimplantsand(b)118Pdimplantsusingacorrelationtimeof2s.116Figure5.19Timingdifferencebetweentheandsecond-pulseinadouble-pulsesignalgatedonthe49.3-keVpeakinthesecond-pulseenergyspectruminFig.5.14.decaycorrelatedspectra.Figure5.20Cloverg-rayenergyspectrumincoincidencewithwiththe155.7-keVpeakfromFig.5.14.117Figure5.21Timingdifferencebetweentheandsecond-pulsegatedonthe155.7-keVpeak.5.3.2Double-pulsesinNbsettingAswiththeRusetting,theNbsettingdatamaybewiththedouble-pulsealgorithm.Fig.5.22showstheenergyofthesecond-pulseforthissetting,wherepeaksat32.5,57.1,71.2,94.5,and114.9keVmaybeseen.Veryfewcountsexistedinthespectrumabove500keVand,asmentionedbefore,thiswasnotduetoancutduetoonlargeamplitudeenergysignals.Theredidnotappeartobeanypeaksintheenergyofthegatedaroundanyofthesecond-pulsepeaks.Fig.5.23showsthe-pulseenergygatedonthe57.1-keVpeakasarepresentativeexample.Thecoincidentg-rayspectrumwiththe57.1-keVpeakispresentedinFig.5.24andcontainsapossiblepeakat152keV,andalargerpeakat510.7keV.Withalackofcountsinthesecondenergyspectrumabove500keV,thisappearedunlikelytoarisefrompairproduction,however,aftercorrectingforthecloverefy,therewouldbe530172countsat511keV,whichdidoverlapwithintheuncertaintieswithtwo511countsforeachofthe15338countsinthe57.1-keVpeakintheGeDSSDspectrum.The57.1-keVtransitionwascorrelatedwithallisotopegatesatlongcorrelationtimes(˘2sorgreater)inanamountproportionaltothenumberofimplantsofeachion,atarateofapproximately118Figure5.22Energyofthesecond-pulseforisotopesintheNbsetting.Figure5.23Energyforthegatedonthe57.1-keVpeakforisotopesintheNbsetting.119Figure5.24Coincidentcloverspectrumforthepeakat57.1keVintheGeDSSD.0.68%.Therefore,the57.1-keVtransitionlikelyexistswithinanisotopefardownthedecaychainsofoneoftheimplantedions.Thiswasincontrasttothe49-keVpeakintheRusetting,wheretherewasastrongcorrelationwithfourPIDgateswithA=118in2s,withaweakercorrelationtoallothergates.Here,the57.1-keVtransitionwascorrelatedtoallPIDspotsequally,atverylongtimesafterionimplantation.Thetimingdifferencebetweenthetheandsecond-pulseofthedouble-pulseisshowninFig.5.25,whereahalf-lifeof1.9(2)msisfound.Oneisomericstatethatcouldaccountforthe57.1-keVtransitionliesat3108keVin118Sn,withahalf-lifeof2.52(6)ms[85].However,giventhestatisticsoftheexperimentandtheefofthedetectors,therewouldlikelybeseveralcoincidentgrays(forexample,477and254keV)withenoughstatisticstobevisibleincoincidence(Fig.5.24),howevertheywerenotclearlypresent.Giventheslightmiss-matchbetweenthe118Snhalf-lifeandtheobservedhalf-lifeandthelackofcoincidenttransitions,thiswaslikelyanunknowntransitionthatisunabletobeinthecurrentwork.Thecoincidentcloverspectraforthepeaksotherthanthe57.1-keVpeakdidnotappeartohaveanycoincidenttransitions.Asecondpeakthatwascorrelatedinisotopegatesliesat71.2-keV.ThispeakwaspresentinPIDgatescontaining109Nband109Mo(Fig.5.26).Previouswork[31]120Figure5.25Decaycurvegatedonthe57.1-keVpeak.Ahalf-lifeof1.9(2)msisfoundfromthewith280(40)decays.establishedanisomericstatein109Moat69.7keVwithahalf-lifeof0.194+0:0760:049ms.Thehalf-lifecurvesinthisworkforeachofthetwoisotopegatesinFig.5.26areshowninFig.5.27.WhiletheredidappeartobeslightdifferencesbetweenthetwospectrainFig.5.27duetothedifferentwaysinwhichtheisomericstatewaspopulated(inpanel(a),agrowthanddecaycurvepopulatedfromahigherexcitedstatein109Moandinpanel(b),fromthebdecayof109Nbintotheisomericstate),thereisnotenoughstatisticsineithergatetosatisfactorilythecurves.Finallytherewasapeakat67.8keVcorrelatedwith107/110Nbimplantation.Thesecond-pulseenergyspectrumisdisplayedinFig.5.28foracorrelationtimeof1s.Previousworkfoundanisomericstateat65keVwithahalf-lifeof420nsin107Mo[86].Thehalf-lifecurveforthistransitionisillustratedinFig.5.29.Aswiththeotherlow-statisticshalf-lifecurves,theplotinFig.5.29wasdiftoThespectruminFig.5.22hasafewotherpeaks,thoughthe33-keV,95-keV,and115-keVpeaksdidnotappeartobeassociatedwithanyPIDgatewithinthebeamsetting,nordidthesepeaksappearinthedouble-pulsespectrumfromthedatatakenimmediatelyaftertheexperimentended.Thesepeaksdidnotappeartohaveanycoincidentgraysinthecloverspectraorinthe121Figure5.26Energyofthesecond-pulsefor(a)109/112Moimplantsand(b)106/109Nbimplants.Bothspectraareshownfora5scorrelationtime.122Figure5.27Timingdifferencebetweenthetwopulsesfor(a)109/112Moimplantsand(b)106/109Nbimplants.123Figure5.28Second-pulseenergycorrelatedto107/110Nbimplantswithin1s.Figure5.29Timingdifferencebetweentheandsecond-pulseforthepeakat67keVcorrelatedto109/112Moimplantswithin1s.124energypulsespectra.Thehalf-lifecurvesforthesethreepeaksareshowninFig.5.30.Inpanel(a),the33-keVpeakwassmall,soitwaslikelythatmanyofthecountswithinthehalf-lifecurvecorrespondtobackground.Withnocoincidenttransitionsandnoclearcorrelationtoparticularimplants,itwasdiftoidentifytheseremainingtransitions.Noclearcandidateswerefound.Figure5.30Timingdifferencebetweentheandsecond-pulsegatedforthe(a)33-keV(b)95-keV(c)115-keVpeaks.1255.4b-delayedgraysInthissection,b-delayedgrayswiththevariousPIDgatesarepresented.Wheremultipleb-delayedgrayswereobserved,relativeintensitiesarecalculated.Forisotopeswithsufcountswithintheirspectra,theTKEseparationtechniquediscussedinSection4.3.2wasapplied.Nonewb-delayedgrayswereineitherproductionsetting.Theobservedb-delayedgraysaresummarizedinTable5.4.Forisotopeswhererelativeintensitieswereabletobedetermined,thesearesummarizedinTable5.5.Table5.4Summaryoftheb-delayedgraysobservedinthiswork.ProducedDaughterLiteratureReferenceThisWorkIsotopeEnergy115Rh115Pd127.8,125.8[74]126.6118Rh118Pd378.6,434.0,574.6[73]378.4,434.0,574.6116Rh116Pd340.3,397.7[70]340.3,397.8115Pd115Ag125.5[69]125.7118Pd118Ag125.4,379.7[83]125.7,378.1118Pd118Ag256.6,326.1[87]256,326.9114Ru114Rh127,179.7[88]126.1,178.3113Tc113Ru98.5,164.3[4]98.4,164.8114Tc114Ru265.1,298.0,443.0,563.4[71]264.9,298.3,442.5,563.2112Tc112Ru236.8,511.5[89]236.0,5105.4.1RusettingTherewere11cleargatesinthePIDfortheRusetting,whichareshowninFig.5.31.Whiletheprevioussectiondiscussedthegraysassociatedwiththeimplantationof115/118RhandwasusedtothePIDanddemonstratetheTKEseparation,otherPIDgroupsalsocontainedpreviouslyknowngrays.Table5.6showthetotalnumberofimplantsforeachgroupinthePID,whereFdenotesafully-strippedion,HdenotesanH-likeion,andHedenotesaHe-likeion.Unlessotherwisenoted,thecorrelationtimeintheseimageswas500ms.126Table5.5Summaryofgrayrelativeintensitiesobservedinthiswork.ProducedDaughterEnergyLiteratureRelativeReferenceThisWorkIsotopeIntensity118Rh118Pd378.4100,100[73],[88]100434.010.0(4),15(2)23(13)574.621.4(12),42(5)49(21)116Rh116Pd340.3100[70]100397.832.6(41)32.7(16)113Tc113Ru98.4100[4]100164.35460(38)114Tc114Ru264.9100[71]100298.325(3)22(15)442.525(3)27(16)563.229(5)55(24)Table5.6NumberofimplantedionsanddecaysintheRubeamsettingusingacorrelationtimeof500ms.IsotopeChargestatesNumberofImplantsNumberofDecays118/121/124AgHe,H,F14212412115/118PdHe,H55048992116/119PdHe,H38906719117/120PdHe,H14272700115/118RhH,F618311075116/119RhH,F75065997117/120RhH,F32666270112/115RuH,F13212402113/116RuH,F35846856114/117RuH,F23154391115/118RuH,F302668127Figure5.31PIDwithsomeofthegroupslabeledwiththechargestatecontaminants.Labelsinblackarefully-strippedions,bluecorrespondstoH-likeions,andredisforHe-likeions.5.4.1.1115/118RhTherelativeintensitiesoftheisotopesusedtodeveloptheTKEseparationtechniquemaybecal-culatedforthe118Rhb-delayedgrays(Fig.4.9).Twopreviousresultsgavedifferingrelativeintensities,whichwerecomparedtothepresentworkinTable5.7.Therelativeintensitiesinthisworkagreedwiththevaluesfromthepreviousworks.Table5.7Tabulatedrelativeintensitiesforthegraysobservedinthedecayof118Rh.Energy(keV)ThisworkRef[88]Ref[73]378.4100100100434.023(13)15(2)10.0(4)574.649(21)42(5)21.4(12)1285.4.1.2116/119RhThemostintensegroupinthePIDcontainedthe116/119Rhions.Thereweretwopreviouslyknown116Rh[70]b-delayedgraysclearlyobservedinthedataat340and398keV.Therelativeintensitiesofthe340-keVand398-keVtransitions,aftercorrectingfortheefy,were100and32.7(16),respectively.Thiscomparedveryfavorablywithpreviousliteratureresultsof100and32.6(41)[70].Figure5.32b-delayedg-rayspectrumcorrelatedto116/119Rhwithin500ms.Previously116Rh[70]graysaremarked.TheTKEseparationtechniquesfortheedgestripsinthedetectordiscussedinSection4.3.2canbeusedwiththisPIDgatetoseparateoutthe116Rhgrays.ThesubsetofeventsfrominFig.5.32wheretheionwaslocatedintheedgestripsoftheGeDSSDisdisplayedinFig.5.33.TwogateswereappliedtotheImage2positionvsenergyspectrumshowninFig.5.34.Theleftgatewasexpectedtohaveanenhancedcontributionfrom116Rhwhereastherightgateswasexpectedtohaveanenhancedcontributionfrom119Rh.ThegrayspectragatingontheleftandrightTKEgatesaregiveninFig.5.35and5.36respectively.The340-keVtransitionwas,again,veryclearlyseeninFig.5.35(116Rh),whileitwasnon-apparentinFig.5.36(119Rh),indicatingareasonableseparationbetweenchargestates.Unfortunately,nob-delayedgraysbecameapparentinthe129119Rhb-delayedspectrum.Ofthetotalnumberofeventsobservedintheedgesofthedetector,45.5%liewithinthe(left)116Rhgateand23.9%liewithinthe(right)119Rhgate.Theobservednumberofcountsat340and398keVwerecomparedtotheexpectednumberofcountsiftherewasnoTKEseparationdeterminedbytakingthepeakintensitiesinFig.5.33andscalingbythepercentageofionsintheTKEgate.ThisissummarizedinTable5.8,whichfurtherdemonstratestheTKEchargestateseparationtechnique.Figure5.33b-delayedg-rayspectrumcorrelatedwith116/119RhforeventstotheedgestripsoftheGeDSSD.Previouslymeasured116Rhgrays[70]arelabeledwiththeirenergiesinkeV.Table5.8Observedcountsfortransitionsin116Rhand119RhdecayscomparedtotheexpectednumberofcountsiftherewerenoTKEseparation.Theexpectednumberofcountsweredeter-minedbyscalingthetotalnumberofimplantsforthenumberwithineachgate.NumberofScaledNumberofScaledGateTotalinObserved340340keVObserved398398keVTKEGatekeVCountsCountskeVCountsCountsAllEdgeEvents57444223-167-116Rh(left)2614311019613873119Rh(right)1345001020042130Figure5.34Image2positionvs.thesumofthePINandGeDSSDenergiesgatesonthe116/119Rhimplants.Ontheleftis116Rhandontherightis119Rh.Figure5.35b-delayedg-rayspectrumcorrelatedwith116/119Rhandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof116RhwasappliedtotheSeetextfordetails.131Figure5.36b-delayedg-rayspectrumcorrelatedwith116/119Rhandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof119RhwasappliedtotheSeetextfordetails.5.4.1.3115/118PdFig.5.37showstheb-delayedgrayscorrelatedwith118/115Pdwithin500ms,where118PdwastheH-likechargestateand115PdwastheHe-likechargestate.Both118Pdand115Pdhaveapreviouslyreported[69,83,84]graytransitionat125keV.The118Pdbdecayalsoleadstoa379-keVtransition,thoughthepeakinFig.5.37wasataslightlylowerenergy.However,baseduponpreviousresults[69]anon-coincident255-keVtransitionshouldbemoreintensethanthe125-keVtransitionfromthe115Pddecay.Atransitionat255keVwasnotapparentinthePID-gatedb-delayedg-rayspectruminFig.5.37.TheTKEgatingtechniquecanbeappliedtotheedgesofthedetectorinthiscaseaswell.ForthesubsetofeventstotheedgesoftheGeDSSDfromFig.5.37,Fig.5.38showstheb-gatedcloverspectrum.TwogateswereappliedtotheImage2positionvs.energyplotinFig.5.39.Theleftgatewasexpectedtoenhancethecontributionfrom115Pdwhereastherightgatewasexpectedtohaveanenhancementfrom118Pd.Fig.5.40showsthehistogramgatedfor115Pd(left).The125-keVgrayremained,buttherewasnoappearanceofa255-keVgray.Based132Figure5.37b-decayg-rayspectrumcorrelatedto115/118Pdwithin500ms.Refs.[83,84]pre-viouslyreported125-keVand379-keVtransitionsinthedecayof118Pd.Ref.[69]reportedat125-keVtransitioninthedecayof115Rh.uponpreviousrelativeintensities,17countsat255keVwouldbeexpected.InFig.5.41(therightgate),theb-delayedg-rayspectrumgatedon118Pdisshown.Whilethe378-keVtransitionwasclear,the125-keVgraywaslessobvious,despitepreviousresults[83,84]indicatingthe125-keVtransitionasthemostintensegray.Baseduponthenumberofcountswithinthe378-keVpeakinFig.5.41,38countsofthe125-keVpealin118Pdgateontheedgestripswouldbeexpected.5.4.1.4116/119PdTheb-delayedg-rayspectrumcorrelatedto116/119PdispresentedinFig.5.42.TherewereafewpreviouslygrayspresentintheH-andHe-like116/119Pdgate.Previous116Pdbdecayresults[83]reportedatransitionat114keV,whichwasdiftoidentifyinthePreviousresultsfor119Pd[87]indicatedtransitionsat256and326keV,thelattermaybeseeninFig.5.42,andtheformerappearstohaveafewcountsabovethebackground.Themostintensetransitionintheliteraturepreviouslyoccurredat130keVandwasnotobservedinthespectrum.TherewerenotenoughcountswhentheeventstotheedgesoftheGeDSSDtoapplythe133Figure5.38b-delayedg-rayspectrumcorrelatedwith115/118PdforeventstotheedgestripsoftheGeDSSD.Previouslymeasuredgraysaremarked.Figure5.39Image2positionvs.thesumofthePINandGeDSSDenergiesgatesonthe115/118Pdimplants.Ontheleftis115Pdandontherightis118Pd.134Figure5.40b-delayedg-rayspectrumcorrelatedwith115/118Pdandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof115PdwasappliedtotheSeetextfordetails.Figure5.41b-delayedg-rayspectrumcorrelatedwith115/118Pdandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof118PdwasappliedtotheSeetextfordetails.135TKEtechnique.Figure5.42b-decayg-rayspectrumcorrelatedto116/119Pdwithin500ms.Ref.[83]reportsa91.0keVtransitioninthedecayof116Pd.Afewgraysknownfromthedecayof119Pdareseenhere:256.6,and326.1keVasreportedin[87].Thereisalsowhatmaybeapeakat340keV.5.4.1.5114/117RuTheb-decayg-rayspectrumcorrelatedto114Ruand117RuimplantsisdisplayedinFig.5.43.Afewgrayswerepreviouslyinthedecayof114Ru[88].Thethreemostintensegrayswereatenergiesof127,128and180keV,ofwhichpeaksappearinFig.5.43.TherewerenotenoughcountswhentheeventstotheedgesoftheGeDSSDtoapplytheTKEtechnique.5.4.1.6AllotherPIDgatesAlloftheotherPIDgatesdidnothaveanyobviousb-delayedgrays.ArepresentativespectrumisshowninFig.5.44.136Figure5.43b-decayg-rayspectrumcorrelatedto114/117Ruwithin500ms.Peaksnear125and179keVlikelyarisefromthedecayof114Ru[88].Figure5.44b-delayedg-rayspectrumcorrespondingtothe117/120RhPIDgateillustratingthelackofclearlyvisiblegrays.1375.4.2NbsettingIntheNbsetting,thereare15cleargroupsinthePIDTable5.9summarizesthenumberofeventsforeachisotopegate.ThelabeledPIDforthissettingisdisplayedinFig.5.45.Allentriesinthetablehavetheheaviermassioninthefully-strippedchargestateandthelighterionintheH-likechargestate.Forthegatescontaining115Ru,thenumberofimplantationanddecaysareshownfortwocorrelationtimes,asthelongercorrelationtimewasusedforhalf-lifedeterminationandtheshortercorrelationtimewasusedtogeneratetheenergyspectradiscussedinSection5.2.Thenumberofdecaysrelativetothenumberofimplantsinthe250mscorrelationtimewassmallduetotheb-decayhalf-lifeofthegroundstateof115Rubeing318ms[12].Table5.9NumberofimplantsanddecayswiththeNbbeamsetting.IsotopeCorrelationTimeNumberofImplantsNumberofDecays112/115Ru250ms664613500ms6641033113/116Ru500ms17162640114/117Ru500ms12461936115/118Ru250ms510559500ms510931109/112Tc500ms549825110/113Tc500ms44647670111/114Tc250ms40873973112/115Tc500ms17183026113/116Tc500ms5881110107/110Mo500ms657968108/111Mo500ms23713687109/112Mo500ms16102860110/113Mo500ms6281134106/109Nb500ms641938107/110Nb500ms525886138Figure5.45PIDplotfortheNbsettingwiththeisotopegateslabeled.Blacklabeledisotopesarefully-strippedandbluelabeledisotopesareH-like.5.4.2.1110/113TcThe110/113TcPIDgroupwasoneofthemoststronglypopulatedgroupsinthissetting.Forthisiso-tope,acorrelationtimeof500mswasused.Theb-delayedg-rayspectrumisshowninFig.5.46.Twopreviously[4]b-delayedgraysfromthedecayof113Tcwerevisibleat98and164keV.Additionally,themostintensetransitionfromthedecayofthe113Rudaughterwasalsovisibleat263keV[90].Withalongercorrelationtime,thepeakat263keVwasmoreapparent,strengtheningtheargumentthatthiswasatransitionresultingfromthedecayofthedaughter.Pre-viousworkindicatedarelativeintensitiesof100and54%forthe99-keVand164-keVtransitions,respectively[4].Aftercorrectingforefy,therelativeintensitiesofthetwotransitionsinthecurrentworkare100and60(38)%.Veryfewcountswereobservedforthelighterchargestate;thereforetheeffectsoftheTKEseparationtechniquearenotdiscussedhere.139Figure5.46b-decayg-rayspectrumcorrelatedto110/113Tcwithin500ms.The98.5-keVand164.3-keVgrayspopulatedinthedecayof113Tcarereadilyapparent[4].Additionally,the263.2-keVtransitioninthedaughterdecayisalsovisible[90].5.4.2.2111/114TcForthe111/114Tcgroup,a250mscorrelationtimewasutilized.Thehalf-livesfoundinpreviousstudiesof114Tcforthetwob-decayingstateswere88and100ms[71].Thepreviouslyobservedhalf-lifefor111Tcwas290ms[33].Severalpreviously-id[71]114Tcgrayswereapparentat265,298,443,and563keV.Therelativeintensitiesofthe265-keV,298-keV,443-keV,and563-keVtransitionswere100,25(3),25(3),and29(5)respectivelyintheliterature[71].Inthepresentdata,theintensitieswerefoundtobeconsistent,being100,22(15),27(16),and55(24),respectively.Again,theTKEgatesmaybeappliedtotheGeDSSDtoseparatethetwochargestates.Theb-decayg-rayspectrumdisplayedinFig.5.47isconstrainedtoeventsattheedgesoftheGeDSSDinFig.5.48.TheImage2positionvs.TKEisgiveninFig.5.49,wherethegateontheleftwasexpectedtoenhanceeventsassociatewith111Tc,whiletherightgatewasexpectedtoenhance114Tcevents.Fig.5.50showsthecloverspectrumforthe111Tc(left)gate.Theremaybeasmallnumberof563keVtransitionsfromthedecayof114Tcinthisgate.Fig.5.51illustratestheTKE140Figure5.47b-decayg-rayspectrumcorrelatedto111/114Tcwithin250ms.Severalofthe114Tcgraysareapparent.AsreportedinRef.[71],thegrayenergiesareat265.1,298.0,443.0,563.4keV.fortheheavier114Tc(right)ion.Severaloftheb-delayedgrayswereapparentinthespectrum,includingthepreviouslyknown265-keV,298-keV,and443-keVtransitions[71].The563-keVgraywashardertoclearlypickoutfromthebackground.Table5.10summarizesthenumberofexpectedcountsintheabsenceofTKEseparatecomparedtothenumberofobservedcountswithintheobservedtransitions.5.4.2.3112/115TcAthirdPIDgatetoproduceb-delayedgraysassociatedwiththedecayof112/115Tcwasappliedtothedata.Theb-delayedg-rayspectrumwithacorrelationtimeof500msisshowninFig.5.52.Agrayat236keVinFig.5.52matchedaknowngrayintheH-like112Tcdecay[89],aswellasperhapsagrayat511keV.However,thehigherenergytransitionwasnotthesecondmostintensetransitionpreviouslyreported.ThereweretoofewstatisticstoperformtheTKEseparationanalysis.141Figure5.48b-delayedg-rayspectrumcorrelatedwith111/114TcforeventstotheedgestripsoftheGeDSSD.PreviouslymeasuredgraysarelabeledbyenergyinkeV.Figure5.49Image2positionvs.thesumofthePINandGeDSSDenergiesgatesonthe111/114Tcimplants.Ontheleftis111Tcandontherightis114Tc.142Figure5.50b-delayedg-rayspectrumcorrelatedwith111/114Tcandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof111TcwasappliedtotheSeetextfordetails.Figure5.51b-delayedg-rayspectrumcorrelatedwith111/114Tcandtotheedgestrips.AnadditionalrequirementontheTKEoftheionsexpectedtoenhancethedecaysof114TcwasappliedtotheSeetextfordetails.143Table5.10Observedcountsfortransitionsin111Tcand114TcdecayscomparedtotheexpectednumberofcountsiftherewerenoTKEseparation.Theexpectednumberofcountsweredeter-minedbyscalingthetotalnumberofimplantsforthenumberwithineachgate.NumberofScaledNumberofScaledGateTotalinObserved265265keVObserved298298keVTKEGatekeVCountsCountskeVCountsCountsAllEdgeEvents20164318-1510-110Tc(left)668001460053113Tc(right)880342019810464NumberofScaledNumberofScaledGateTotalinObserved443443keVObserved563563keVTKEGatekeVCountsCountskeVCountsCountsAllEdgeEvents201696-1612-110Tc(left)66800324254113Tc(right)88074436375Figure5.52b-decayg-rayspectrumcorrelatedto112/115Tcwithin500ms.The236.8-keV,andpossiblyasmallamountofthe511.5-keVtransitioninthedecayof112Tcisvisible[89].1445.4.2.4109/112MoContinuingtothe109/112Mo,PIDgroup,the236-keVtransitionfromthedecayofthe112Tcdaughter,112Ru,wasapparentinFig.5.53.Theb-delayedg-rayspectruminFig.5.53wasgener-atedwithacorrelationtimeof500ms.ThereweretoofewcountstoperformtheTKEseparationtechnique.Figure5.53b-decayg-rayspectrumcorrelatedto109/112Mowithin500ms.The236.8-keVtran-sitioninthedecayofthedaughter112Tcisvisible[89].5.4.2.5AllotherPIDgatesUtilizingthegrayspresentedthusfar,thegatesinthePIDplotmaybeunambiguouslylabeled.WiththeexceptionofPIDgroupscontaining115Ru(seeSection5.2),therewerenoapparentb-delayedgraysintheothergates.ArepresentativespectrumisshowninFig.5.54.145Figure5.54b-decayg-rayspectrumcorrelatedto108/111Mowithin500ms.Nob-delayedgraysareapparent.146CHAPTER6CONCLUSIONSANDOUTLOOK6.1ConclusionsAvarietyofdifferentnuclearstructureexperimentshavebeensuccessfullycarriedoututilizingtheGeDSSD.ThepresentstudyfocusedontheA˘110neutronrichregionofthenuclearchart,inparticularonTcandRuisotopes.NucleiwithA˘110havebeenlongthoughttoexhibitlargeprolatedeformations,withtheopenquestionofwhetherthenuclearshapeshiftstoamoresphericaloranoblateshapeathigherA.Inadditiontogroundstatespinsandparities,isomericstatesareanimportanttestofthenuclearstructureintheregion.Inparticular,g-rayandconversionelectronspectroscopyaretoolsthatmaybeusedinthediscoveryandofisomericstates.TheGeDSSDdiscussedwithinthisdocumentisparticularlywellsuitedforthesestudies,asitshighdetectionefyforlow-energygraysandconversionelectronsprovideamethodtoquantifyinternaltransitionsdeexcitingisomericstates.Severalisomerictransitionswereinvestigated.Inparticular,anisomericstateof115Ruwasplacedinthe115Rulevelsschemeviaconversionelectronandg-rayspectroscopyat123.8keVwithahalf-lifeof85(13)ms.Thisisomericstatedecayedvizacascadeoftwograyslessthan1keVapartinenergy.Previousresultsestablishedthepresenceofadecayingisomer,butdidnotplacethestateatanenergy.Thepresentworksuggeststhatthemultipolarityofthe61.7keVtransitionisM1.Thetransitionoutoftheisomericstateistherefore62.1kevinenergy,andthepreviouslyM2multipolaritywaskeptinthiswork.WiththepresenceofnegativeparityisomericstatesintheheaviestRuisotopes,theh11=2orbitallikelyplaysaroleintheirnuclearstructure.Itisdiftoexplainthetentativespinsandparitiesoftheground-states,withprolatesuggestingperhapsatransitiontomoresphericalorevenoblatenuclei.Inotherisotopicchains,previouslymeasuredisomericstatesin118Agat49and155keVweremeasuredbythedouble-pulseprocessingtechnique,aswerepreviously-measuredisomericstatesin107Moand109Moat14767.8and71.2keVrespectively.Severaltechnicalandanalyticaldevelopmentswerediscussed.TheGeDSSDwasveryefcientforbothb-decayelectronsandb-delayedgrays.ThisworkcharacterizedtheGeDSSD,establishingtheexpectedcorrelationefy,aswellasthedetectorsresponsetotheimplanta-tionofheavyions.Whileadvantageousfordetectingavarietyofdecaymodesandlow-intensitytransitions,thehighefyforelectronsandgraysledtoanincreasedcomplexityofanalysisduetothepossibilityofb-gsumming.Thus,thedevelopmentofanalgorithmtore-createtheenergydepositedonapixel-by-pixelbasisfromthestripreadoutwasinvestigated,andresultswerepromising.Anothertechnicalissuethataroseinexperimentswastheproductionofmultiplechargestatesoftheionsimplantedinthedetectorthatcreatedambiguitieswithintheparticleiden-OnewidespreadtechniquetoseparatechargestatesisthroughaTotalKineticEnergymeasurement.Aftercorrectingfortheeffectsofchargesharingandcross-talkwithintheGeDSSD,thetotalenergyoftheimplantedionswasmeasured,andusedforaTKEmeasurement.b-delayedgrayspectraindicatethetechniquewasabletogiveseparationfortheouteredgesoftheGeDSSD.6.2OutlookForfutureworkintheregionofA˘110,thenextinvestigationshouldbetheisomericstatesofodd-ARuisotopes.Anisomericstatewaspreviouslyin113Ru,thoughthisstatehasnotbeenplacedataveenergy.Theexcitedstatesknownin117Rudonothaveevententativespinandparityassignments,anditisofinteresttoinvestigatewhetherthepatternofnegativeparityisomericstatescontinuesintoheaviernuclei.ConversionelectronspectroscopyperformedbydetectorsliketheGeDSSDcanhelptoinfermultipolaritiesandthereforetheofisomericstates.Finally,datafromodd-Anucleiinthisregionisneededtohelpintheunderstandingoftheevolutionofnuclearstructureintheregion,andtoinvestigatewherethepredictedtransitionsinshapebetweenprolateandeitheroblateorsphericalnucleioccursintheisotopicchainsintheregion.148ThesuccessfulcommissioningoftheGeDSSDpavesthewayforthedevelopmentoffuturede-tectorsofthistype.TheexperimentaladvantagesofGeovermoretraditionalSihavebeendemon-strated,manifestinginincreasedefyandsensitiveisomerspectroscopy.ThereareseveralchangesthatwouldimprovetheTKEmeasurementtechnique.Minimizingnon-activematerialinfrontoftheGeDSSDcrystalwouldresultinfewerenergylosses,andlessenergystraggling,makingtheTKEmeasurementeasier.Theamountofmaterialcouldbereducedbythecreationofasimilardetectorthatisconnecteddirectlytothevacuumofthebeampipe,eliminatingtheKaptonwindow,cryostat,Alradiationshield,andairthebeammustpassthrough.Additionally,theonthebacklow-gainstripswerehoundtosaturate,preventinganaccurateenergydetermination.Restoringthecapabilitytousetwosetsofstripsforindependentenergydetermi-nationwouldaidanalysis.Anotherpossibilitytoimproveanalysiswouldbetoreadoutenergiesinpixelsratherthaninstrips,removingtheneedtoreconstructeventsfromthestripenergies.Thiswould,ofcourse,comeatthecostofrequiringmanymoreDDASmodulesandcabling.Itwasalsomorediftodeterminetheefyofthedetectorsviastandardizedsourcesthananticipated.Onealternatepossibilitywouldbetodevelopabeamwithwell-knowng-rayactivityandcalibratetheefythatway,reducingoreliminatingtheneedtorelyonsimulation.Finally,greaterstripsegmentationwouldimprovetheanalysis.Greatersegmentationmeansamorepreciseloca-tiondetermination,whichinturnwouldallowforhigherimplantationrates.Greatersegmentationwouldalsoreducetheeffectsofb-gsumming,assmallerpixelsgivetheparticlesgreatersolidangleinwhichtoseparate.TheGeDSSDisapowerfulspectroscopictool,butitismoreexpensiveandislesshardytoradiationdamagecomparedtoitsSicounterparts.However,theSidetectorsdonothavethesamelow-energyg-rayefy.Anotheroptionsometimesusedinb-decaystudiesisasegmentedplasticscintillator.However,thiscomesatacostoftheenergyresolution.Inorganicscintillators,suchasYAP,aresometimesused,thoughtheirresolutioniscomparabletoNsIdetectors,whichislessthanthatofGe.OnecouldimplantintoaLaBr3detector,butLaBr3hasalargeinternalactivity,whichwouldmakecorrelationmoredifandnomanufacturersaresegmentingdetectorsof149thistype.OnealternativewouldbetomovetoCeBr3,astheCeBr3detectorshavelessinternalactivitycomparedtoLaBr3,althoughthecostmaybeprohibitive.InordertoreplacetheGeDSSDforthisapplication,adetectorwouldhavetohavegoodenergyresolutionforbothelectronsandgrays,mustbeabletodeterminethepositionofeventsforcorrelation,andtheremustbealowincidenceofinternalactivity.150BIBLIOGRAPHY151BIBLIOGRAPHY[1]W.Loveland,D.J.Morrissey,andG.T.Seaborg.ModernNuclearChemistry.JohnWiley&Sons,Inc.,NewJersey,2006.[2]P.WalkerandG.Dracoulis.Energytrapsinatomicnuclei.Nature,399:35Œ40,1999.[3]W.Urban,A.GSimpson,J.A.Pinston,J.Kurpeta,T.Rza¸ca-Urban,J.L.Durell,A.G.Smith,B.J.Varley,N.Schulz,andI.Ahmad.Newspinsforgroundstatesandisomersin115pdand117pd.TheEuropeanPhysicalJournalA,22:157Œ161,2004.[4]J.Kurpeta,G.Lhersonneau,J.C.Wang,P.Dendooven,A.Honkanen,M.Huhta,M.Oinonen,H.Penttilä,K.Peräjäarvi,J.R.Persson,A.andÄystöJ.Firstdecayschemeof113tcandof113rum.TheEuropeanPhysicalJournalA,2:241Œ243,1998.[5]J.Kurpeta,J.Rissanen,A.W.Urban,V.V.Elomaa,T.Eronen,J.Hakala,A.Joki-nen,A.Kankainen,P.Karvonen,T.wicz,I.D.Moore,H.Penttilä,A.Saastamoinen,G.S.Simpson,C.Weber,andÄystöJ.Newisomeranddecayhalf-lifeof115ru.PhysicalReviewC,82:064318,2010.[6]N.Larson,S.N.Liddick,M.Bennett,A.Bowe,A.Chemey,C.Prokop,A.Simon,A.Spyrou,S.Suchyta,S.J.Quinn,S.L.Tabor,VandanaTai,P.L.Tripathi,andJ.M.VonMoss.Highefybeta-decayspectroscopyusingaplanargermaniumdouble-sidedstripdetector.NuclearInstrumentaandMethodsinPhysicsResearchA,727:59Œ64,2013.[7]S.HeydeandJ.L.Wood.Shapecoexistenceinatomicnuclei.ReviewsofModernPhysics,83:1467Œ1521,2011.[8]V.R.Pandharipande,R.M.Singru,andR.P.Sharma.Decayofpd111andpd111m.PhysicalReview,140:1488Œ1496,1965.[9]H.Penttilä,T.Enqvist,P.P.Jauho,A.Jokinen,M.Leino,J.A.Parmonen,andJ.Äystö.b-decayof113rhandtheobservationof113mpd:Isomersystematicsinodd-apalladiumisotopes.NuclearPhysicsA,561:416Œ430,1993.[10]W.John,F.W.Guy,andJ.J.Wesolowski.Four-parametermeasurementsofisomerictransi-tionsin252cffragments.PhysicalReviewC,2:1451Œ1469,1970.[11]W.Urban,T.Rza¸ca-Urban,Ch.Droste,S.G.Rohozi´nski,J.L.Durell,W.R.Phillips,A.G.Smith,B.J.Varley,N.Schulz,I.Ahmad,andJ.A.Pinston.Newbandsandspin-parityassignmentsin111ru.TheEuropeanPhysicalJournalA,22:231Œ239,2004.[12]J.Rissanen,J.Kurpeta,A.V.V.Elomaa,T.Eronen,J.Hakala,A.Jokinen,A.Kankainen,P.Karvonen,I.D.Moore,H.Penttilä,S.Rahaman,ASaastamoinen,W.Ur-ban,C.Weber,andJ.Äystö.Penning-trap-assistedstudyof115rubetadecay.TheEuropeanPhysicalJournalA,47:97Œ105,2011.152[13]J.Kurpeta,W.Urban,A.J.Rissanen,V.V.Elomaa,T.Eronen,J.Hakala,A.Joki-nen,A.Kankainen,P.Karvonen,I.D.Moore,H.Penttilä,A.Saastamoinen,C.Weber,andJ.Äystö.Signaturesofoblatedeformationinthe111tcnucleus.PhysicalReviewC,84:044304,2011.[14]P.Möller,J.R.Nix,W.D..Myers,andW.J.Swiatecki.Nuclearground-statemassesanddeformations.AtomicDataandNuclearDataTables,59:185Œ381,1995.[15]S.HilareandM.Girod.Large-scalecalculationsfromprotontoneutrondriplinesusingd1sgognyforce.TheEuropeanPhysicalJ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