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6/01 C'JCIRC/DateDuepGS-pts

CHARACTERISTICS AND MODELING OF MINIATURE MICROWAVE PLASMA
DISCHARGES CREATED WITH MICROSTRIPLINE TECHNOLOGY

By

Jeffri Julliarsa Narendra

A THESIS
Submitted to
Michigan State University
in partial fulﬁllment of the requirements
for the degree of
MASTER OF SCIENCE
Department of Electrical and Computer Engineering

2004

ABSTRACT

CHARACTERISTICS AND MODELING OF MINIATURE MICROWAVE PLASMA
DISCHARGES WITH MICROSTRIPLINE TECHNOLOGY

By

Jeffri Julliarsa Narendra

Recently, interests in the development of a system on a chip, MEMS and
their related micro system applications have suggested the possibility of
numerous applications for mini and micro plasma sources. The primary objective
of this thesis is to develop such a miniature plasma source and understand the
discharge behavior created by it. The plasma source designed in this research is
based on the microstrip transmission line structure. The stripline has a
characteristic impedance of 50 ohms and is connected to a 2.45 GHz microwave
power operating at 1 - 100 Watts. The plasma was created inside a tube, with an
inner diameter of 2 mm or less, that was orientated perpendicular to the stripline
conductor. This design allows the creation of an electrodeless plasma discharge.

Several diagnostic techniques were utilized to characterize the miniature
discharges. Gas temperature and electron density analysis was performed using
optical emission spectroscopy (OES). The electron temperature and electron
density measurements were performed using the double Langmuir probe (DLP).
The results from the DES and DLP experiments are compared to the global
analytical model. The power densities for argon discharges created by this
source vary from 10's to over 800 chm3 and the plasma densities as indicated

by the modeling work are in the range of 1012-1015 cm'3.

ACKNOWLEDGMENTS

I would like to take this opportunity to thank my major professor, Dr.
Timothy A. Grotjohn, for his constant encouragement and excellent guidance that
led me through the work presented here. Along with my advisor, I would like to
thank Dr. Jes Asmussen and Dr. Donnie K. Reinhard for being part of the
examining committee. Their valuable suggestions and advice are greatly
appreciated.

I would also like to thank Kadek W. Hemawan, Andy Wijaya, and Stanley
Zuo, who have helped me in the course of this study. A word of thanks is also
due to Dr. John T. Hinnant for proof reading the manuscript.

Finally I would like to thank my family for their love and their constant

support for my graduate studies.

iii

TABLE OF CONTENTS

LIST OF TABLES .................................................................................. vi

LIST OF FIGURES ............................................................................... vii

CHAPTER 1

Introduction

1.1 Motivation .................................................................................... 1

1.2 Objectives .................................................................................... 2

1.3 Thesis Outline ............................................................................... 2

CHAPTER 2

Literature on Miniature Plasma Sources and Diagnostic Technique

2.1 Miniature plasma sources ............................................................... 4
2.1.1 Microstripline structure ....................................................... 7
2.1.2. Microstripline plasma source ................................................. 9

2.2 Plasma diagnostic techniques ......................................................... 10
2.2.1 Optical emission spectroscopy ............................................. 10
2.2.2 Langmuir Probe technique ................................................... 11

CHAPTER 3

Equipment and Experimental Method

3.1 Introduction to equipment ............................................................... 13

3.2 Plasma reactor system ................................................................ . 13
3.2.1 Introduction. .................................................................... 13
3.2.2 Microwave system ............................................................. 13
3.2.3 Gas/vacuum system .......................................................... 16

3.3 Microstripline designs .................................................................... 17
3.3.1 Microstripline coupling structure #1. ...................................... 19
3.3.2 Microstripline coupling structure #2. ...................................... 22

3.4 Optical Emission Spectroscopy setup ............................................... 23
3.4.1 Spectrometer system ......................................................... 23
3.4.2 Optic collection ................................................................ 24
3.4.2 Data collection ................................................................. 25

3.5 Double Langmuir Probe setup ........................................................ 26
3.5.1 Probe ............................................................................. 26
3.5.2 Data collection ................................................................. 27

CHAPTER 4

Microstripline Plasma Source Performances

4.1 Introduction ................................................................................. 29

4.2 Ignition Process ........................................................................... 29

4.3 Tuning Behavior .......................................................................... 30

iv

4.4 Volume of Plasma ....................................................................... 32

4.5 Power Density Measurement ......................................................... 39
4.6 Discharge Branch and Loop ........................................................... 44
4.7 Conclusion ................................................................................. 48
CHAPTER 5
Investigation Using Optical Emission Spectroscopy
5.1 Introduction ................................................................................ 49
5.2 Gas Temperature ........................................................................ 49
5.2.1 Gas temperature measurement theory ................................... 49
5.2.2 Gas temperature of H2 .......................................................... 53
5.2.2.1 Experiment procedure ................................................. 53
5.2.2.2 Experimental results ................................................... 56
5.2.3 Gas temperature of N2 .......................................................... 57
5.2.3.1 Experiment procedure ................................................ 57
5.2.3.2 Experimental result .................................................... 61
5.3 Stark broadening ......................................................................... 63
5.4 Conclusion ................................................................................. 67
CHAPTER 6
Investigation Using Langmuir Probe
6.1 Introduction and brief review of Langmuir probe diagnostic ................... 68
6.2 Experimental setup ...................................................................... 71
6.3 Result and discussion ................................................................... 74
6.4 Conclusion ................................................................................. 75
CHAPTER 7
Global Model Calculations
7.1 Introduction ................................................................................ 76
7.2 Theoretical background ................................................................ 76
7.3 Results and discussions ............................................................... 82
CHAPTER 8
Summary and Recommendations
8.1 Summary ................................................................................... 90
8.2 Recommendations ....................................................................... 92
APPENDICES ................................................................................... 94
REFERENCES ................................................................................ 130

LIST OF TABLES

Table 3.1: Conversion of Opthos microwave power supply output power
reading to the actual output power ............................................. 15

Table 3.2: Dimension of the microstripline coupling structure ....................... 18

Table 4.1: Operating condition for igniting argon discharge in 2 mm
diameter tube ........................................................................ 30

Table 5.1: Rotational constants for the electronic states of hydrogen
and nitrogen ......................................................................... 50

Table 5.2: Energy Level for the R branch of the G‘z;——>e‘>:..* (0-0) band
of H2 molecule. .................................................................... 54

Table 5.3: Energy Level for the R branch of the (2,0) SPS system
of nitrogen discharge. ............................................................. 60

Table 5.4: Coefﬁcient a for electron density estimates and the ﬁne structure
splitting for H3 and H5 lines of hydrogen Balmer series. .................. 64

Table 5.5: Measured plasma density from Stark broadened H5 and H5 lines
of hydrogen. ........................................................................ 66

Table 7.1: Comparison of the charge density calculated using global model
and measured from the Stark effect. .......................................... 89

vi

LIST OF FIGURES

Figure 2.1: Microstripline with trace stmcture ............................................. 7
Figure 3.1: Schematic of the test circuit to calibrate the microwave power

supply ............................................................................... 14
Figure 3.2: Schematic of the Microwave system ........................................ 15
Figure 3.3: Schematic of the gas/vacuum system ...................................... 17
Figure 3.4: Microstripline coupling structure with discharge tube placed

underneath the copper line ..................................................... 18
Figure 3.5: Two dimensional view of the Microstripline coupling structure ....... 21

Figure 3.6: Microstripline coupling structure with discharge tube placed
across a gap in the copper line ............................................... 22

Figure 3.7: Schematic of the Optical Emission Spectroscopy measurement 24

Figure 3.8: Cross sectional view of the Double Langmuir probe tips .............. 27
Figure 3.9: Schematic of the Double Langmuir Probe measurement .............. 27
Figure 4.1: Tuning characteristic of the microstripline applicator ................... 31

Figure 4.2: Variation of argon discharge length and absorbed microwave
power at different stub positions. Discharge diameter: 1 mm,
Input power: 13 W, ﬂow rate: 50 sccm, pressure: 20 Torr,
Microstripline system #2 ........................................................ 32

Figure 4.3: Variation of discharge volumes at different Pm. Discharge tube
diameter: 1 mm, Pressure: 0.24 — 3 Torr, feed gas: pure argon,
flow rate: 20 sccm, microstripline system #2. ............................ 34

Figure 4.4: Variation of discharge volumes at different Pam. Discharge tube
diameter: 1 mm, pressure: 10 - 200 Torr, feed gas: pure argon,
ﬂow rate: 20 sccm, microstripline system #2. ............................ 34

Figure 4.5: Comparison of discharge volume vs. P2,. of different microstripline

applicators. Discharge tube diameter: 1 mm, pressure: 10 Torr,
feed gas: pure argon, flow rate: 20 sccm. ................................. 35

vii

Figure 4.6: Discharge volumes variations at different Pam for argon discharges
created using microstripline system #1. Flow rate: 20 sccm,
discharge tube size: 1 mm ..................................................... 35

Figure 4.7: Discharge volume variations for different Pm in argon discharges
created using microstripline system #1. Pressure: 10 Torr,
discharge tube size: 1 mm. .................................................... 36

Figure 4.8: Discharge volume variations for different Pam in argon discharges
created using microstripline system #1. Pressure: 10 Torr,
ﬂow rate: 20 sccm. ............................................................... 36

Figure 4.9: Discharge volume variations for different Fab. for Ar, Ar-H2
(95%-5%), H2, and N2 created using microstripline system #1.
Pressure: 5 Torr, discharge tube size: 2 mm. ............................. 37

Figure 4.10: Variation of discharge power density at different Pm.
Discharge tube diameter: 1 mm, Pressure: 0.24 - 3 Torr, feed gas:
pure argon, ﬂow rate: 20 sccm, microstripline system #2. ............. 40

Figure 4.11: Variation of discharge power density at different Pm.
Discharge tube diameter: 1 mm, Pressure: 10 - 200 Torr, feed gas:
pure argon, ﬂow rate: 20 sccm, microstripline system #2. ............. 40

Figure 4.12: Comparison of discharge power density vs. Pan. of different
microstripline applicators. Discharge tube diameter: 1 mm,
pressure: 10 Torr, feed gas: pure argon, ﬂow rate: 20 sccm. ......... 41

Figure 4.13: Discharge power density variations at different Pan. for argon
discharges created using microstripline system #1.
Flow rate: 20 sccm, discharge tube size: 1 mm. ......................... 41

Figure 4.14: Discharge power density variations for different Pan. in argon
discharges created using microstripline system #1. Pressure:
10 Torr, discharge tube size: 1mm. ........................................ 42

Figure 4.15: Discharge volume variations for different Pat, in argon
discharges created using microstripline system #1. Pressure:
10 Torr, ﬂow rate: 20 sccm. ................................................... 42

Figure 4.16: Discharge power density variations for different P.“ for At,
Ar-H2 (95%-5%), H2, and N2 created using microstripline
system #1. Pressure: 5 Torr, discharge tube size: 2 mm. ............. 43

Figure 4.17: Top view of argon discharge branching inside the 2 mm id.
quartz tube. ........................................................................ 45

viii

Figure 4.18: Top view of argon discharge inside a loop of 2 mm id.
quartz tube. ......................................................................... 46

Figure 4.19: Side view of argon discharge inside a loop of 2 mm id
quartz tube. At low Pm, discharge does not completely ﬁll up
the loop (a); at high Pat... argon discharge ﬁlls the loop completely
(b) with the exception of a small gap on the top of the oval. ........... 46

Figure 4.20: F ilament-like discharges observed for argon feed gas at
atmospheric pressure. ........................................................... 47

Figure 5.1: An example of vibrational and rotational energy levels with
a number of transitions in the P, Q, and R Branches. ................... 52

Figure 5.2: Emission spectra of the R Branch of the G‘Xg+ —> B122“+
(0—0) band of H2 molecule. ...................................................... 54

Figure 5.3: Boltzmann plot for the lines R0 and R5 - R10 of H2 plasma. ........... 55

Figure 5.4: Variation of rotational temperature of H2 with ﬂow rates for H2
plasma. Pressure: 0.5 Torr, Pine: 33 W. ..................................... 56

Figure 5.5: Variation of rotational temperature of H2 with different Ar ﬂow
rates in H2 - Ar plasma. Pressure 0.5 Torr, Pm: 33 W,
H2 ﬂow rate: 2 seem ............................................................... 57

Figure 5.6: Variation of rotational temperature of H2 with different pressure

for H2 plasma. Pine: 33 W, H2 ﬂow rate: 2 sccm ............................ 57
Figure 5.7: Spectrum of nitrogen discharge showing the band heads

of the SPS system ................................................................. 58
Figure 5.8: Fine structures of the (2,0) SPS system of nitrogen discharge

that were used for rotational temperature measurement ................ 59
Figure 5.9: Boltzmann plot for the lines R20 — R30 of N2 plasma ..................... 60

Figure 5.10: Variation of rotational temperature of N2 with different
pressure for N2 - Ar plasma. Pine: 33 W, ﬂow rate: N2-2 sccm,
Ar-18 sccm ........................................................................... 61

Figure 5.11: Variation of rotational temperature of N2 with different

Ar ﬂow rates in N2 — Ar plasma. Pressure 0.5 Torr,
Pine: 33 W, N2 ﬂow rate: 2 sccm ................................................ 62

ix

Figure 5.12: Variation of rotational temperature of N2 with different
pressure for pure N2, and mixtures of Ar - N2

(50% Ar, and 90% Ar) discharges ............................................ 62
Figure 5.13: The observed broadened H3 hydrogen Balmer line. ................. 65
Figure 5.14: The observed broadened H5 hydrogen Balmer line .................. 66
Figure 6.1: Typical current — voltage (l-V) characteristic. ............................ 69

Figure 6.2: Theoretical shape of the saturation current portion of the probe
characteristic for various probe shapes when the probe is
limited by orbital motions. ..................................................... 71

Figure 6.3: I-V curves obtained using DLP diagnostic. Pressure: 10 Torr,
Pm: 2.34 Watts, Gas: Argon, ﬂow rate: 10 sccm. ...................... 72

Figure 6.4: Log plot of the I-V characteristic from DLP diagnostic.
C=l+l1lI2-l, A=A1IA2. ............................................................. 73

Figure 6.5: Variations of electron temperature for different pressures.
Gas: Argon, flow rate: 10 sccm, Pm: 2.34 Watts, Discharge
tube size: 2 mm, Microstripline stmcture #1. ............................. 74

Figure 6.6: Variation of charge density for different pressures.
Gas: Argon, ﬂow rate: 10 sccm, Pm: 2.34 Watts, Discharge
tube size: 2mm, Microstripline structure #1. .............................. 75

Figure 7.1: T3 versus ng-deﬁ for Maxwellian electrons in argon [13]. ............... 77

Figure 7.2: Collisional energy loss per electron-ion pair created, 3:. versus
Te in argon discharge (compiled by Vahedi, 1993) [13]. ................ 79

Figure 7.3: Te versus n9*A for non-uniform argon discharge
(compiled by P.Mak, 1994) [ECE989A]. .................................... 80

Figure 7.4: Comparison of the electron temperatures of argon discharges
created in system #1 and system #2. ....................................... 83

Figure 7.5: Comparison of the electron temperatures between the global
model calculations and the results from DLP. ............................. 84

Figure 7.6: Peak charge density of argon discharge created using
microstripline structure #1. Discharge tube size: 2 mm id. 85

Figure 7.7: Peak charge density of argon discharge created using
microstripline structure #1. Discharge tube size: 1 mm id. ............ 86

Figure 7.8: Peak charge density of argon discharge created using
microstripline structure #2. Discharge tube size: 1 mm id. ............ 87

Figure 7.9: Comparison of calculated charge density from global model
and measured charge density from DLP diagnostic ..................... 88

xi

Chapter 1

Introduction

1.1 Motivation

This research project involves investigating and establishing the scientiﬁc
basis and engineering principles for the design and operation of small microwave
plasma sources with discharge dimensions ranging from 1.0 mm — 2.0 mm. Past
investigations on microwave discharges by researchers have primarily focused
on discharges that were a few centimeters to almost a meter in size. However,
careful investigations of microwave discharges with dimensions on the order of
few millimeters have not been done, especially in the GHz frequency range. The
emphasis in this project is on developing plasma sources that will operate without
the electrode erosion and contamination problems of small plasma electrode-
based systems that are used in arc systems and plasma displays. Small
microwave discharges operate with a low input power. This allows the sources to
operate with coherent and controllable power supplies currently available for
mobile communication system with power levels of one to a few watts.

The thesis intends to experimentally evaluate and subsequently model the
behavior of microwave discharges as the discharge size is decreased. The
microwave plasma system being used is a microstripline based plasma source.
Some of the experimental conditions/structures investigated include varied
discharge radii, a variety of discharge gas types (inert gas-argon, and molecular

gases-nitrogen and hydrogen), both low and high pressure regimes, a range of

ﬂow rates giving short to long gas residence times in the discharge chamber, and

range of plasma discharge geometric aspect ratios.

1.2 Objectives

The primary objective of this work is to design a new miniature plasma
source based on microstripline technology and to develop an understanding of
the fundamental characteristics of the discharge created by this source.

To achieve this objective, two microstrip transmission line coupling
structures were designed and tested. The performance of those structures was
compared in terms of the coupling efﬁciency needed to generate the discharge.
The fundamental characteristics studied were the electron temperature, gas
temperature, and electron density. The studies were performed on A., H2, N2, and
mixtures of Ar - H2 and A, - N2 discharges at various pressures ranging from 0.5

Torr to 760 Torr.

1.3 Thesis outline

This thesis will focus on observing the characteristics of a discharge that is
generated using two microstripline coupling structures. Chapter 2 discusses the
literature on miniature microwave plasma sources and diagnostic techniques
used in the research. The discussion includes a description of the microstripline
transmission line. Chapter 3 explains the experimental systems. These include
the testbed system and diagnostic equipment used in the experiments. Chapter
4 details the performance of the microstripline plasma source. The observations

for various modiﬁcations on the system along with the interpretations are

discussed. In chapter 5, the rotational temperature measurements of hydrogen
and nitrogen plasmas using optical emission spectroscopy (OES) are presented.
The study of the Stark broadening effect in a hydrogen plasma, which can
determine the electron density, is discussed as well. The relevant details needed
to understand the optical emission spectroscopy methods are provided. In
chapter 6, the electron temperature and density measurements, using double
Langmuir probe (DLP), in low pressure argon discharge are presented. Chapter
7 discusses the numerical modeling of argon discharges’ characteristics. The
results are compared with the DES and DLP results. Finally, chapter 8 concludes

the research and provides recommendations for future research.

Chapter 2

Literature on Miniature Plasma Sources and Diagnostic
Techniques

2.1 Miniature microwave plasma sources

The deﬁnition of plasma according to Chen [1] is a quasineutral gas of
charged and neutral particles which exhibits collective behavior. There is always
some small degree of ionization in any gas; however, any ionized gas cannot be
called a plasma. The plasma is quasineutral; that is, neutral enough so that the
density of electrons and ions are equivalent (ne 5 in), but not so neutral that all
the interesting electromagnetic forces vanish.

A fundamental characteristic of the behavior of a plasma is its ability to
shield out electric potentials that are applied to it. This shielding is called the
Debye shielding. The quantity zip, called the Debye length, is a measure of the

shielding distance or thickness of the sheath.

8 K T
ADE I‘D—iii (2.1)
nee

where so is the permittivity of free space, K3 is the Boltzmann’s constant, T, is the

electron temperature, n.9 is the charged density far away from the shield, and e is

the electron charge. Often, the Debye length can be approximated as:

AD z 743 [Ze— (cm) (2.2)
"e

where T, is in eV and n9 is in cm‘3.

The criterion for an ionized gas to be a plasma is that it be dense enough that 1.0
is much smaller than the dimension of the system (L). In addition, the number of
particle (ND) should be large enough inside the shielding so that the concept is
statistically valid. Lastly, the frequency of typical plasma oscillations (mp9) times
the mean time between collisions with neutral atoms (1) should be greater than 1
for the gas to behave like a plasma rather than a neutral gas. Those three
criterions can be represented as:

1.3.0 <<L
2. ND = ne gel?) »1 (2.3)

3.0)per>l

The ﬁrst criterion of a plasma indicates that the small-scale plasma source
will create a high density discharge. Different small-scale plasma sources have
been developed by several research groups. Yin et al. [2] has investigated a
miniaturization of inductively coupled plasma (ICP) sources. The discharge in this
ICP source is conﬁned within the 4 mm id. of a discharge tube. The electron
temperature of the argon plasma created using this ICP source is found to vary
between 3 eV and 9 eV and the charge density is in the range of 109-1010 cm'3.

A plasma gun, developed by Hartog et al. [3], is capable of producing a

clean, high density (1013 — 10“ cm"), low temperature (T,- zTe zS—lSeV)

plasma for pulse length of at least 40 ms. The gun operates using molybdenum
electrodes and it produces a plasma about 5 cm length and 3 cm diameter. A

stack of washers is used to deﬁne the arc channel between the anode and

cathode. The major impurities reported in this gun plasma are boron, carbon, and
nitrogen from the boron nitride washers and molybdenum from the metal
electrodes.

Stoffels et al. [4] designed a plasma needle for ﬁne surface treatment of
bio materials. This radio-frequency (RF) excited plasma source operates under
atmospheric pressure. Plasma appears as a small glow at the tip of a metal pin
with a dimension of 5 cm long and 1 mm diameter. The characteristic dimension
of a helium plasma generated using this source does not exceed 0.1 - 0.2 mm
and the electron density is on the order of 1013 - 10“ cm'3.

At Michigan State University, small microwave discharges’ characteristics
have been studied since the early 1980’s by Asmussen et al. [5 — 7]. Rogers [5]
investigated the discharge properties of argon plasma columns with diameters of
1 — 3 mm and length up to 16 cm. The discharge was excited using a 2.45 GHz
magnetron inside a microwave cavity. Quartz tubes of varying diameter were
used to conﬁne the gas. The tubes ran coaxially inside the cavity. Typical
electron densities for argon discharges at 1 atrn were 3x1013 cm‘3 to 3x1 0“ cm'3.

Brake [6] studied the Stark broadening effect of a mixture of hydrogen -
argon discharge generated using a surface wave launcher. The plasma was
contained in a 4 mm id. quartz tube, situated vertically, with pressure ranging
from 50 - 1000 Torr. The electron density measurements of this work agreed
with Rogers’ data.

The electron density of microwave—generated surface wave discharges in

argon have been measured using Stark broadening and calculated from the

measured wavelengths of the standing surface wave by Brake et al. [7]. Results
obtained from these two techniques compare well. The electron density varies

from 1013 cm'3 to 10“ cm‘3 for pressures ranging from 50 to 800 Torr.

2.1.1 Microstripline structure

Microstripline is one of the most popular transmission line structures. The
structure of a microstrip transmission line is shown in ﬁgure 2.1. The structure

consists of a ground plane, a dielectric layer, and a stripline trace.

I w
Stripline tra ____________ i ..

 

    

A‘u‘AA‘AL‘A-AAAAL- AAA-Al-‘l lA-AA‘MAIA

Ground Plane

 

 

 

‘—"—T—’

 

Figure 2.1 Microstripline with trace structure
There are various calculation techniques used to determine the
characteristic impedance for this structure. Wadell [8] summarized Bogatin’s

experimental comparison of these calculations and recommended using the

Wheeler equation with Schneider’s 8917.

 

I P 2 ﬂ
4h 14+% 4h 14+ +% 4h 2 1+%
710 1m ———ejZ———+ eﬂ {—J +——ei’:7r2 )

1+—
w 2

Ozzﬁnigeﬂu w 11 3 11

 

 

 

 

 

(2.1)

where 770 is the characteristic impedance of free space (in O), 39” is the effective

relative dielectric constant, h is the dielectric height, w is the conductor strip width.

For %.<_1:

—0. 5 2
821;» = 3’2” + 8’2’1[(1 1:53] +0.04(1—1;—) ] (2.2)

 

 

a, +1 .9, _1( my“

a: + l+—-——
eﬂZ 2 w

(2.3)

where a, is the relative dielectric constant. The equations for a,” are accurate to
within 1% for:

a, 516 (< 2% error 3, >16)

0.05 _<_ % s 20.0 (< 2% error V11 <0.05)

The thickness of the trace t can be corrected for by relating it to an equivalent

change in the width (Aw) using the following equation:

M = im 4 e (2.4)

W Mu]-

The error in 20 is less than 2% for any a, and w.

 

 

 

 

 

The minimum width of the ground plane and the dielectric layer (T) should
be more than the width of the trace (w) to minimize the effect on Z0 and £9”. The

effect is a function of frequency. At DC, the ground current will be spread equally

through the ground cross-section; however, as frequency increases, it will

concentrate into a strip directly below the microstripline. The ideal ratio 3% 2 2.

2.1.2 Microstripline plasma source

Bilgic et al. [9-10] have designed a miniature plasma source using
microstrip technology. The microstrip plasma source (MSP) basically consists of
a planar microstripline on fused silica used as the dielectric substrate and a
massive copper ground plate which also serves as a heat sink. The microstrip
transmission lines are designed for about 50 Ohms wave impedance without the
plasma. The plasma-gas channel(s) are inside the dielectric substrate below the
microstripline with a cross section of 1 mm2. The plasma is encapsulated within
the dielectric, and is not affected and contaminated by the surrounding
atmosphere. A stable argon plasma can be achieved for a gas ﬂow range of 50 -

1600 ml min'1 at a microwave forward power of 10 - 40 W. When the plasma gas

is very low, no homogeneous plasma is formed in the MSP device but some
small stable discharges between the two edges of the gas channel close to the
electrodes can be observed. When increasing the Ar gas ﬂow, these discharges
start to overlap in the direction of the gas ﬂow and to form one plasma, which

homogeneously ﬁlls the whole discharge channel cross section.

2.2 Plasma diagnostic techniques

There are many different methods for measuring the plasma parameters.
The diagnostic techniques which are presented here deal with the measurement
of the microwave energy density, gas temperature, electron temperature, and
charge density. Those discharge characteristics are considered to be the
important features that can describe the nature of a discharge. The most
commonly used diagnostic techniques are Optical Emission Spectroscopy and

Langmuir probe diagnostics.

2.2.1 Optical emission spectroscopy

Optical Emission Spectroscopy (OES) analyzes the spectrum of light
(photons) emitted by the species in the plasma. One of the simpler applications
of OES is species identiﬁcation, because different atoms or molecules emit
different wavelengths in the spectrum. The OES can also provide semi-
quantitative information on the concentration of the species. In this research,
however, species and its concentration are provided as the input parameters.

The OES is also able to measure the translational temperature from a

Doppler-broadened discharge. Broadening arises from the Doppler shift caused

10

by thermal particle motion giving rise to the line proﬁle. However, the perturbation
of rotational energy levels by molecular collisions (pressure broadening)
becomes the limiting factor for the line resolution.

For a molecule which has quantum states of rotation, rotational
temperature can be measured for the emission spectrum. A number of
experiments investigating the rotational temperature of hydrogen [11, 12] and
nitrogen [4, 13, 14] discharges have been found in the literature. This technique
is used in this research to obtain the gas temperature of the discharge. The
detailed description of this diagnostic is presented in section 5.2

The electron density in a discharge can be measured by observing the
Stark effect using an OES system [3, 15]. The Stark effect phenomenon occurs
when an emitting species is in an electric ﬁeld. An experiment to obtain the

electron density from the Stark effect is explained in section 5.3.

2.2.2 Langmuir probe diagnostics

A Langmuir probe is a metal probe inserted into a discharge. The probe is
usually small; therefore, the perturbation to the discharge is minimal. The
concept of probe diagnostics is that a bias voltage is applied to the probe to
collect the electron or ion current. Common conﬁgurations for the probe
diagnostic includes: a single Langmuir probe, a double Langmuir probe, and an
emissive probe. The electron temperature, electron density, discharge ﬂoating
potential, discharge potential, and electron energy distribution function of a
discharge can be identiﬁed using the single Langmuir probe conﬁguration.

However, this conﬁguration needs a ground electrode in the discharge.

1]

If there is no well-deﬁned ground electrode in the discharge, as in the
microstripline plasma source developed in this research, the double probes or
emissive probe conﬁgurations are used to do the diagnostics. The double
Langmuir probes can identify the electron temperature and electron density.
Thus, the double probe conﬁguration is used in this research. A detailed
discussion of the double Langmuir probe diagnostics for the discharge generated

using microstripline coupling structure can be found in chapter 6.

12

Chapter 3

Equipment and Experimental Methods

3.1 Introduction to equipment

This chapter describes the features of the miniature plasma source
apparatus. In the ﬁrst section, the testbed system is explained, including the
microwave system and gas/vacuum system. The microstripline coupling
structures’ design are explained in detail in section 3.3.

The equipment setup for measurements and characterizations of the
discharges are also described in this chapter. There are two techniques used in
these experiments, Optical Emission Spectroscopy (OES) and Double Langmuir

Probes (DLP) Diagnostics.

3.2 Plasma reactor system

3.2.1 Introduction

The system used for the experiment can be divided into three main parts;
they are the microwave system, the gas/vacuum system, and the microstripline

coupling structure.

3.2.2 Microwave system

Microwave energy is supplied by a 2.45 GHz Opthos Instrument, Inc.
microwave power supply which has an operating power range from 1 Watt to 120

Watts. The actual output power from the power supply was calibrated using a

13

simple test circuit, as shown in ﬁgure 3.1. The reading from the Opthos power
supply was compared to the reading from the power meter. The power meter
was connected to the -10 dB directional coupler. A directional coupler has an
input port, an output port, and a sampling port. 10 dB of the signal from the input
port goes to the sampling port, whereas the rest of the signal goes to the output
port. The reverse transmission from the output port to the input port of the
directional coupler is lossless. The signal from the directional coupler was further
attenuated by a proper attenuator to maintain the signal at the power meter
range. A calibrated directional coupler and attenuator were used in this setup.
The forward line of the directional coupler was connected to a dummy load.
Microwave power coming from the attenuator was detected by a HP 432 power
meter. The conversion of the power meter reading by the microwave power

supply and the actual output power is given in table 3.1.

 

Directional
Microwave Coupler

Supply Load

ttenuator

 

 

 

 

 

 

 

 

Power
Meter

 

 

 

Figure 3.1 Schematic of the test circuit to calibrate the microwave power supply

14

Table 3.1: Conversion of Opthos microwave power supply output power
reading

 

The microwave circuit is designed to have a characteristic impedance of
50 ohms. The circuit includes a CT-3695-N UTE Microwave three port circulator,
a 50 ohms Thermaline Coaxial resistor model 8085 as the dummy load, two
Narda model 3003-10 coaxial directional couplers, three feet and six feet coaxial
cables with N-type connectors, a HP 432A power meter, a General Radio Type-

874 20 cm adjustable stub, and attenuators.

    
   
 

 
  

   
  
 

 

 
 
 
 

 

 
 

- Directional Microstripline

Microwave Crrculator A Couplers

power —

Supply Adjustable

stub
N-type \
Connectors Quartz
tube

 

Load Power Power
Meter Meter

( Incident) (Reﬂected)

 

 

 

 

 

 

Figure 3.2 Schematic of the Microwave system

The conﬁguration of the microwave circuit is shown in ﬁgure 3.2. The
circulator transfers the microwave energy from the microwave power source into
the system. A dummy load connected to the circulator is used to protect the
power supply by absorbing the reﬂected microwave signal from the system.

Two directional couplers were used in this system to measure the incident
power and the reﬂected power. The input port of the directional coupler (A) was
connected to the circulator via a 3-feet coaxial cable. The directional coupler (B)
was connected in reverse to the directional coupler (A) in order to measure the
reﬂected power from the microstripiline. The power meters were connected to the
sampling ports of each directional coupler. The signals coming from the sampling
ports were reduced by 40 dB attenuators to meet the operating range of the
meter. The total attenuation of the reﬂected power is measured to be -47.5 dB.

The other end of the microstripline is connected to an adjustable stub
which is used to tune the microwave energy so that the maximum amplitude of
the standing wave in the microstripline is in the vicinity of the quartz tube. The

details of microstripline structure will be discussed in section 3.3.

3.2.3 Gas/vacuum system

Gas ﬂow into the discharge tube is controlled through an MKS mass ﬂow
controller. Plastic hose with a diameter of ‘/4 inch is used to carry the gas ﬂow
between gas/vacuum system apparatus. Various discharge tube sizes are used
in this experiment. Discharge pressure is monitored by a HEISE pressure
monitor. The pressure monitor is connected to the plastic hose line between the

quartz tube and the vacuum chamber using a T-branch Swagelok connector. The

16

vacuum chamber/pump apparatus used for lowering the discharge pressure has

been described elsewhere [12].

Pressure

   

 

 

 

Dischar e
Gas Tank Tube 9 Manual Valve
Mass Flow \ \C/icuugn /
Controller \szdgigE-c am er

 

 

 

 

 

 

 

 

 

Pump
5.; \ T System
0.25” plastic Microstripline Swagelok
hose Connectors

 

 

Figure 3.3 Schematic of the gas/vacuum system

There are two ways to control the gas/discharge pressure: ﬁrst by using
the MKS Pressure controller which is embedded into the vacuum chamber/pump
and, second, by adjusting the manual valve opening. The MKS pressure
controller is used for low pressure (1 — 100 Torr) experiments due to the ease of
controllability. For pressure higher than 100 Torr, the manual valve opening is

adjusted to obtain a desired pressure in the discharge tube.

3.3 Microstripline design

Plasmas were generated by applying a high electric ﬁeld via the
microstripline into the feed gases which ﬂow inside the discharge tube. The
discharge tube is orientated perpendicular to the stripline conductor. Two
discharge tube placement designs were investigated. In the ﬁrst design, the tube
was placed between the microstripline and the ground plane (Figure 3.4) and in

the second design, the tube was placed across a gap in the microstripline (Figure

3.6). The inner conductors of two N-type connectors were soldered to the copper

line and outer conductors were screwed onto the aluminum ground plane. A

Teﬂon plane was placed on top of the ground plane as the dielectric medium.

The structure’s dimensions have been calculated so they meet the 50 ohms

impedance matching requirement as discussed in chapter 2. The material

characteristics and dimension are listed in table 3.2.

Table 3.2 Dimension of the microstripline couplin structure

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Materials Length (mm) Width (mm) Thickness (mm) 8,
Copper 102 12 1
Teﬂon 102 50 3.3 2.1
Aluminum 102 50 10
Teﬂon dielectric
/- Discharge Copper line
\ 0
O 0 0
° VVrdth
\
W
N-type Connector W
Thickness ‘—— Length \’
f 4

Aluminum Ground plane

18

I

Quartz tube

Figure 3.4 Microstripline coupling structure with discharge tube placed
underneath the copper line

 

3.3.1 Microstripline coupling structure #1

Microstripline coupling structure #1 as shown on ﬁgure 3.4 and 3.5 was
the ﬁrst system that was used in the experiment. In this applicator, discharge
tube was placed in between the copper and the aluminum ground plane. The
tube was orientated perpendicular to the microstripline.

Transmission efﬁciency was measured by calculating the energy loss
along the transmission line. A low power 2.45 GHz frequency generator was
used to supply 1 Watt of microwave energy into the transmission lines without
the discharge (empty load). The microwave circuit conﬁguration in ﬁgure 3.2 was
modiﬁed to measure the transmission efﬁciency. The microstripline structure
together with the adjustable stub was replaced with a power meter. The
efﬁciency of the transmission line using this conﬁguration was 74%. However,
when the microstripline structure was added to the circuit, the transmission
efﬁciency was dropped to 45%. This indicated that the microstripline coupling
structure is a lossy media or a microwave reﬂecting structure. Nevertheless,
since a plasma is a power absorbing medium, it changes the matching conditions.
The transmission efﬁciency was assumed to be higher than the empty load
measurement. The approximation of power transmitted into the discharge is 59%
of the input power.

Microwave power absorbed by the discharge can be calculated using the
following formula:

Pabs = (Pinc- x 59%) — (Pref x 56,300) (Watts) (3.1)

19

Where Pm is the actual power coming from the Opthos microwave power supply,
59% comes from the approximation of the transmission efﬁciency, Pm, is the
reﬂected power reading from the power meter and 56,300 comes from the -47.5
dB attenuators.

Microstripline structure #1 was used in a number of experiments to
determine the discharge characteristics. A variety of discharge tube sizes can be
used as long as the dimension of the outer diameter of the tube does not exceed
the thickness of the Teﬂon dielectric layer, which is 3.3 mm. Thus a quartz tube
with an inner diameter (id) of 2 mm and an outer diameter of 3 mm can be used
in the experiments. Optical emission spectroscopy and double Langmuir probes
diagnostic were performed using microstripline structure #1 with a 2 mm id.
discharge tube. In addition to the 2 mm id. tube, a 1 mm id. discharge tube was

also utilized in discharge volume and power density measurements.

20

    

122m

 

  

 

 

 

 

 

 

 

 

    
 
 

 

     

 

 

 

 

 

E
E 3 mm -J
N
5:3 groove
A A
Inner
screws to conductor
tTIngitent soldered _
e 0" ° to co er 2
aluminu strip pp 1 mm —TE
69
N-type
AA view connector
Ground plane Stripline Dielectric E
(Aluminum) (Copper) (Teﬂon) E
(0
co'
1

 

 

 

10 mm

 

 

Side View

N-type
Connector
screws to
ground
plane

Figure 3.5 Two dimensional view of the Microstripline coupling structure

21

3.3.2 Microstripline coupling structure #2

Microstripline coupling structure #2 is a modiﬁcation of the applicator
mentioned in the previous section. In this applicator, the discharge tube was
placed across a gap on the copper stripline as shown on ﬁgure 3.6. The other
parts of the structure remain the same as the microstipline structure #1. The
advantage of the structure #2 is that the dielectric layer is uniform across the
plane. Thus, the characteristic impedance of the microstripline is not far off from
the calculated value. However, the gap on the copper stripline promotes a big
radiation leak and a lot of the microwave power reﬂected back into the circuit
before the plasma is ignited. Once the plasma is generated, the radiation leak
and the reﬂected power are greatly reduced. This is because a plasma acts as a
conductor therefore the gap on the conducting microstripline acts as a microwave

energy absorbing load.

 

 

 

 

 

 

 

 

 

 

 

 

m Discharge
[ Copper line
N o
0 0
O Teﬂon dielectric
o
\
N-type Connector \

 

 

 

Aluminum Ground plane

Quartz tube

Figure 3.6 Microstripline coupling structure with discharge tube placed across a
gap in the copper line

22

3.4 Optical Emission Spectroscopy setup

Some of the discharge characteristics were obtained using the Optical
Emission Spectroscopy technique. In this subsection, the setup and equipment

descriptions for OES measurements are explained.

3.4.1 Spectrometer system

The spectrometer used for all of the OES measurements was a
McPherson Model 216.5, 0.5 meter, f/8.7, plane grating monochromator. The
grating has 2400 grooves/mm designed to operate in the wavelength range of

1050 A - 5000 A. The entrance slit and the output slit were set at 20 m wide.

The principle of operation of the monochromator is diffraction. The grating
inside the monochromator diffracts the incoming light and the angle of diffraction
varies with the wavelength. Hence, at any given time, only diffracted light at
particular wavelength comes out to the exit slit. Choosing a speciﬁc wavelength

can be done by rotating the diffraction grating about the axis at a speciﬁc angle.

23

I I Focusing Lens
J - Monochromator

 

   

 

:33; D' h 3:
*1 _______ rscarge ...... :i' Entrance
............................ slit

 

  
  

 

 

 

 

 

 

 

I} G rating

Exit _
_____________ sﬁt

 

 

 

 

 

 

 

multiplier

   

Collimating
mirror

Computer

Figure 3.7 Schematic of the Optical Emission Spectroscopy measurement

3.4.2 Optic collection

The optic signal was collected at the end of the cylindrical discharge, thus
data taken were the average over the whole length of the discharge. In order to
see the discharge at the end of the tube, one of the ports in a T-shape Swagelok
tube connector was modiﬁed to become a viewing window by attaching a 1 mm
thick glass using epoxy. The other two ports in the connector served as a regular
connection for gas ﬂow. Distance between the discharge and the viewing window
was kept as close as possible to minimize the signal loss. A biconvex lens with
the focal length of 5 cm was used to focus the optic signal into the entrance slit of
the monochromator. A black cloth was used to cover the path between the
viewing window and the monochromator in order to block the ambient light, thus

enhancing the signal-to-noise ratio.

24

3.4.3 Data collection

The McPherson spectrometer has a scanning motor which can rotate the
grating to scan the wavelength. The scanning motor has ﬁxed speeds ranging
from 0.5 Almin to 2000 Almin. However, since the spectrometer and the software
for data collection are run independently and are not synchronized, scanning a
wide spectrum using a low scanning speed tends to give an inaccurate result.
This happens because the time it takes for the spectrometer to scan the
spectrum and the time needed for the software to perform data collection differ
by a few milliseconds. Thus, a ﬁx scanning speed of 5 Almin to scan 50 A of
spectrum was chosen to get a maximum result in the spectrum quality factor
without noticeable offset.

The McPherson spectrometer houses an EGI-GENCOM RPI QLIZO
photomultiplier tube (PMT). The PMT converts light signals into electrical signals.
A bias voltage of -900 V is applied to the PMT from the ORIEL 70705 High
Voltage Supply. The output current from the PMT is detected by a Keithley 6485
picoammeter. The picoammeter is connected to a computer by an lEEE-488
(GPIB) interface. The GPIB bus is connected to a National Instrument GPIB card
installed in the computer. A Quick BASIC program is used to record the signals
at the desired interval. The software code is included in appendix B. The

recorded data is then analyzed in Microsoft Excel.

25

3.5 Double Langmuir Probe setup
3.5.1 Probe

A double Langmuir probe was used to measure the electron
characteristics such as the electron density and electron temperature. It is
convenient to use the DLP setup over a single Langmuir probe because there is
no well-deﬁne ground in the plasma created in the glass tube.

Two identical probes are inserted in the discharge with a separation
distance of 0.18 mm. The distance between two probes needs to be longer than
the discharge sheath (3), which is approximately four times the Debye length

(1.0), as described by [16]:

sz4xlD z4x743 FE (cm) (3.2)
"e

where T9 is the electron temperature in eV, and n9 is the electron density in cm'3.
Using approximation values of T, around 2 eV and no is in the order of 1012 cm’3,
the sheath is on the order of a few microns.

The probes were made of tungsten wires with a diameter of 0.1 mm. The
length of the wires exposed to the discharge was 1 mm. Silica tubing with outer
diameter of 0.33 mm and inner diameter of 0.15 mm was used as an insulator to

cover the tungsten wires, with the exception of the tip area.

26

WWW

 

Silica Tubing

 

 

 

 

 

 

 

Figure 3.8 Cross sectional view of the Double Langmuir probe tips

3.5.2 Data Collection

Discharge Gas ﬂow Thick Alligator

quartz Atub/clips

T-conne or DC Power
swagelok SUPPIY

  
    

 

 

 

   

Probe tips _
1/4 Inch

plastic hose

Multi-meter
[:i DLP Box j
V GPIB DC Power
E L—______i Supply
2%. (HP 6634A)

Figure 3.9 Schematic of the Double Langmuir Probe measurement

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

27

Shown in ﬁgure 3.9 is the system setup for DLP data collection. A DC
Power Supply (HP 6634A) delivers potential to the probe via DLP box. The
potential is set by a software consisted of a Quick BASIC program to increase
from 1 Volt to 100 Volts. Since the l-V characteristic desired is in the range of -50
— 50 Volts, a bias voltage of -50 Volts is supplied by another DC power supply to
get the desired voltage range. The current from the probes is recorded by a
multi-meter and collected by the computer. The software code is included in

appendix C. The recorded data is then analyzed in Microsoft Excel.

28

Chapter 4

Microstripline Plasma Source Performance

4.1 Introduction

This chapter describes the discharge behavior and its basic
characteristics. In section 4.2, the ignition procedure is explained for various
gases, pressure, ﬂow rates, and incident powers. Section 4.3 explains the tuning
behavior used to attain maximum power coupling into the plasma. Next, the
volume of the plasma and the power density measurements are presented.
Finally, the behavior of plasma in modiﬁed discharge tubes and the behavior of

the discharge at atmospheric pressure are presented.

4.2 Ignition Process

The procedure for igniting a discharge in this miniature microwave plasma
source is straightforward. First, the mechanical pump was turned on to lower the
pressure in the discharge tube. Second, feed gas was delivered into the
discharge tube by adjusting its ﬂow rate from the mass ﬂow controller. The third
step entailed applying the microwave energy. Prior to conducting the experiment,
a low power test was performed on the microwave circuit. The test was
performed to check the circuit for radiation leaks that may occur and to calibrate
the length of the adjustable stub to achieve a minimum reﬂected power.
Appropriate stub tuning minimizes the reﬂected power, thus enhancing the

performance of the discharge. Plasma acts as a load to the microwave circuit.

29

The plasma existence changes the impedance of the microwave circuit. Hence,
the adjustable stub needs to be re-tuned after the plasma is ignited.

The incident power needed to ignite an argon discharge is around 5 Watts.
However, for hydrogen and nitrogen feed gases, around 20 - 30 Watts of
microwave power is needed to ignite the plasmas. The suitable pressure to ignite
those discharges is around 1 - 3 Torr. An aluminum mesh was used as a
microwave screen to enclose the microstripline coupling structure to prevent
microwave radiation. Once the microwave system and gas/vacuum system were
set, a high voltage spark from a tesla coil was applied to the discharge tube to
ignite the plasma.

For argon feed gas, the discharge can be ignited in the pressure range
from 1 Torr up to 300 Torr. Higher incident power are needed to ignite the
plasma as the pressure increases.

Table 4.1 Operating condition for igniting argon discharge in 2 mm diameter tube.

 

 

 

 

 

 

Incident Flow Rate Maximum
Power (Watts) (sccm) Pressure (Torr)
6.4 25 50

10 25 80

10 35 100

12.8 25 200

19 25 300

 

 

 

 

 

4.3 Tuning behavior

Transmission line impedance matching for this system was done by using
a 20 cm single stub tuner. The operating frequency of the microwave system

was 2.45 GHz. The microwave energy creates a standing wave in the

30

microstripline and the adjustable stub. The stub was used to tune the standing
wave so that the maximum electric ﬁeld was at the discharge tube as shown in

ﬁgure 4.1.

The medium inside the stub is air. The wavelength of the microwave

propagation in air can be found using the following:

2,, = 7f 4.1
where c is the speed of light and f is the microwave frequency. As seen in ﬁgure

’1
4.2, the distance between the maximum power transfers to the load is at 4% or

 

 

 

 

 

 

 

 

 

 

 

 

6.12 cm.
Standing wave ﬁelds Plasma Discharge
in the applicator
k— m —.r
lm /’ WV ----- <———1
1 Ground plane

Adjustable short E\lectnc ﬁeld lines stripline connected

(or open circuit) to the microwave

tuning stub power supply

Figure 4.1 Tuning characteristic of the microstripline applicator

Plasma length in ﬁgure 4.2 is the length of the plasma expansion in the
axial direction (along the tube). The value was obtained by measuring the
distance between both ends of the plasma. As seen in ﬁgure 4.2, the maximum

length is achieved when the absorbed power is at the maximum.

31

 

.3
N

 

 

 

ﬂawsmabmmil
E 10 T !-absorbed power]
0 _ .M#”##*__
g, -_
c 8
2 _ _
g 6 " ’ _ '. ‘i
g - ’o- _ o _-
a .. -______ ____-_--_ .__-_-__
— o
s 4 . °
.3.
Q' 21 o ’
6990 090090900 000000000 009000906
0

 

0 2 4 6 8 10 12 14 16 18 20

Stub length (cm)

Figure 4.2 Variation of argon discharge length and absorbed microwave power at
different stub positions. Discharge diameter: 1 mm, Input power: 13 W, ﬂow rate:
50 sccm, pressure: 20 Torr, Microstripline system #2.

4.4 Volume of plasma

Plasma generated using the miniature microwave plasma source is
conﬁned in the radial direction by the tube. The quartz tube prevents the
expansion of the plasma other than along the tube length. The plasma length can
be adjusted by varying the input power or tuning the adjustable short. Maximum
length of a discharge can be achieved when the adjustable short is tuned
properly as explained in the previous subsection. Thus, the volume of the plasma
is the cylindrical volume that depends on the cross sectional area of the
discharge tube used in the system and maximum length of the discharge. The

plasma sheath was on the order of a few microns as stated in section 3.5. Thus,

32

the sheath was not incorporated in the calculation and the radius of the plasma
was assumed equal to the radius of the tube.

An interesting phenomenon occurred for argon discharge when the power
delivered into the discharge was increased. At very low powers the length of the
discharge matches the width of the Microstripline. In this condition, the
microstripline delivered the power into the discharge in a similar fashion as in the
parallel plate system. However, as the absorbed power increases, the discharge
expanded along the tube. In this case, in addition to the power transferred into
the discharge by a parallel plate, the discharge was maintained by a plasma
surface wave that traveled inside the quartz tube along the discharge.

The analysis of the plasma volume was done for the following gases:
argon, hydrogen, nitrogen, and a mixture of argon-hydrogen. Parameters that
were varied include the microstripline structures, the discharge tube size, the
absorbed power, the pressure, and the gas ﬂow rates. All of the experiments that
use microstripline structure #2 and use discharge tubes that were 1 mm or less in
inner diameter were performed for pure argon gas only.

Some of the experimental results are shown in ﬁgures 4.3 - 4.9. A
complete data listing for different discharge sizes for power density

measurements can be found in appendix D.

33

 

 

 

 

 

 

0.08
0.07 — xg
A ci
”E 0.06 - m
3 o
g 0.05 ~ ’§
3 0.04 g
a, __.________._,
g 0.03 4 500.24 TorrI,
é ‘ D 0.5 Torr I
5 0'02 E :A1Torr ‘
0.01 - I iXZTorr I
135.3 7°"..r
0 . r T r
0 5 10 15
lDabs (watts)

Figure 4.3 Variation of discharge volumes at different Pm. Discharge tube
diameter: 1 mm, Pressure: 0.24 — 3 Torr, feed gas: pure argon, ﬂow rate: 20
sccm, microstripline system #2.

 

 

 

 

 

 

 

0.08
I
0.07 - . ‘
":59 0.06 ~ : A x
E 005 « I x
.3. i A x x
O X
> 0.04 x
8, I x
E 0.03 ~ - _-..
5 I 10 Torr
g 0'02 i ‘ : )1: A50 Torr
0.01 ~ 2 X x 100 Torr
35309191
0 . T
0 5 10 15
Pabs (VVBtlS)

Figure 4.4 Variation of discharge volumes at different Pam. Discharge tube
diameter: 1 mm, pressure: 10 - 200 Torr, feed gas: pure argon, ﬂow rate: 20
sccm, microstripline system #2.

34

 

0.08
0.07 - x

.0

8

x
v

0.05 2 A
0.04 i X A
0.03 -

0.02 - ‘

0.01 - A X System #1 i
@6199 #21

Discharge Volume (on?)

 

 

 

 

0 . T
0 5 10 15 20 25

IDabs (Watts)
Figure 4.5 Comparison of discharge volume vs. P2,, of different microstripline
applicators. Discharge tube diameter: 1 mm, pressure: 10 Torr, feed gas: pure
argon, ﬂow rate: 20 sccm.

 

 

 

 

 

 

0.08
a O
“E 0.07 . . .
3 0.06 9 I - ,,__._________,
CD I I i
E 0.05 - O - ‘ . ‘ O 10 Torr
2 A A X I 100 TO”
0 0 04 y I A x X X
it . o ‘ x X X X .X A 150 Torr
2’ 0.03 ' X X o g x 200 Torr
.2 . X o . +
(3 0.02 - ‘ X + + + x 300 Torr
o 001 ﬁ c400Torr
+ 500 Torr
O a I T “T— m__.___.
0.0 5.0 10.0 15.0 20.0 25.0 30.0
Pabs (Watts)

Figure 4.6 Discharge volumes variations at different Pm for argon discharges
created using microstripline system #1. Flow rate: 20 sccm, discharge tube size:
1 mm.

35

olume (on?)

>

Discharge

 

 

 

 

 

0.08
0.07 - X x E x g
0.06 ~ A '3 D '3
U
K
0.05 . D
0.04 ~ 0
E,“ o o
- x .---_ __ ,_ _
0.03 A r02sccm i
I
0.02 - U n10$ccm
0 01 ° 1 A 20 sccm i
' 1x40 scc_rr_rj
0 . ,
0.0 5.0 10.0 15.0 20.0 25.0
Pabs (Watts)

Figure 4.7 Discharge volume variations for different Pm in argon discharges
created using microstripline system #1. Pressure: 10 Torr, discharge tube size: 1
mm.

Discharge Volume (chi)

 

 

 

 

0.6
- I
0.5 l
I
0.4
0 3 ] 713$]
' l2mmJ
0.2
I
0.1 .
I O O
o ’ . .
O r ‘r T
0 5 10 15 20 25
Pabs (Watts)

Figure 4.8 Discharge volume variations for different Pm in argon discharges
created using microstripline system #1. Pressure: 10 Torr, ﬂow rate: 20 sccm.

36

 

 

 

 

 

0.6
. o

A 0.5 o
”E o
3

0.4 -_-__ —
g ’ oArcon
3 _ . lAr-H2 I
i 0'3 . AHydrogeni
(E; LXJ'E'BQE’U
.‘c"a 0.2
e— . .
o 01 f I I

' o . I

* IX ‘ x A X A X A X A X
0 r . . -
0 5 10 15 20 25

Pabs (Watts)
Figure 4.9 Discharge volume variations for different P». for Ar, Ar-H2 (95%-5%),
H2, and N2 created using microstripline system #1. Pressure: 5 Torr, discharge
tube size: 2 mm.

From ﬁgure 4.3 and 4.4 it is seen that the volume of argon plasma
increases as the absorbed power increases. In the low pressure range (0.24 — 3
Torr) the discharge volume shows little variation versus pressure. However, for
higher pressure range (10 — 200 Torr), the volume of argon plasma decreases as
the pressure increases. The maximum volume for argon discharge, created using
microstripline system #2, inside a 1 mm tube, was 0.07 cm3. A maximum
discharge volume can be reached when the pressure is set to 10 Torr or lower
and the absorbed power is around 16 Watts.

Figure 4.5 shows a comparison for different microstripline coupling

structure designs. It can be seen that, with similar input parameters, system #1

gave a better performance for Pain less than 10 Watts. However, the volume

37

expansion tends to saturate for P2,. higher than 10 Watts. On the other hand,
discharge volume and Pam have a linear relationship for system #2. The
observed argon plasma volume never exceeds 0.08 cm3 for both systems using
1 mm discharge tube.

Argon discharges created using microstripline system #1 show little
variation in their volume for pressures higher than 300 Torr, as can be seen in
figure 4.6.

When the ﬂow rate of the gas through the system was varied with the
other parameters held constant, a slight decrease in discharge volume was
observed with decreasing ﬂow rate in the range 10 — 40 sccm as seen in ﬁgure
4.7. However, at 2 seem, the discharge volume was noticeably smaller compared
to the higher ﬂow rate. Wrth higher ﬂow rate, supply of the argon species to the
system was higher. Consequently, the volume of the discharge increased as the
ﬂow rate increased.

From ﬁgure 4.8, it can be observed that argon plasma created inside the 2
mm tube had a bigger volume than those created inside the 1 mm tube. Plasma
length can be derived from the discharge volume since the cross sectional areas
of both tubes differed by a factor of 4. By investigating the plasma length, it can
be concluded that the surface wave maintained discharge is slightly larger for the
2 mm tube.

Figure 4.9 shows that the surface wave excitation was dominant in
maintaining the argon discharge, whereas hydrogen and nitrogen discharges

showed only a little variation in volume as the absorbed power increases.

38

4.5 Power density measurement

Power density in Watts per cubic centimeter (chm3) was determined by
taking the ratio of the absorbed microwave power and the plasma volume. The
total absorbed power calculation has been described in section 3.4, whereas the
volume of the plasma is given in section 4.4. All of the absorbed power was
assumed to go into creating the plasma.

The analysis of the power density was done for the following gases: argon,
hydrogen, nitrogen, and a mixture of argon-hydrogen. Parameters that were
varied include the microstripline structures, the discharge tube size, the absorbed
power, the pressure, and the gas ﬂow ratcs. All of the experiments that use
microstripline structure #2 and use discharge tubes that were 1 mm or less in
diameter were performed for pure argon gas only.

Some of the experimental results are shown in ﬁgures 4.10 —- 4.16. A
complete data listing for different discharge sizes for power density

measurements can be found in appendix D.

39

300

 

 

 

 

 

 

x
250 <2 '
mg 8 x2
3 200 o E!
4:: RE
:5 xi )1)
‘2 1 1{$0.24 Torr-
g 100 U 0.5 Torr
o
0. IA 1 Torr
50 » ix 2 Torr
I} 1119:;
0 T ’ r
0 5 10 15
Pabs (Watts)

Figure 4.10 Variation of discharge power density at different Pat... Discharge tube
diameter: 1 mm, Pressure: 0.24 — 3 Torr, feed gas: pure argon, ﬂow rate: 20
sccm, microstripline system #2.

 

 

 

 

500
450 — x
A 400 . x
"E -
i 350 ‘ x x x
300 ~
.é‘ X X
g 250 . ' x x
a) ‘ X A I‘
9 200 . x‘ . u
0 A I _____-,
§ 150 I [:10 Torr I
100 . ,A50 Torr r
50 4 ‘X 100 Torr
(520010";
0 . T" F T
0 5 10 15
Pabs (W395)

Figure 4.11 Variation of discharge power density at different Pam. Discharge tube

diameter: 1 mm, Pressure: 10 — 200 Torr, feed gas: pure argon, ﬂow rate: 20
sccm, microstripline system #2.

40

 

350

 

 

 

 

 

 

300 ' X
A X
”‘E’ 250 ‘
S A x A
.a ‘
C A x
8 150 ‘
d; X
8 100 x
50 x IiSystemi’]
X A System #21
0 _ T
0 5 10 15 20 25
Pabs (Watts)

Figure 4.12 Comparison of discharge power density vs. P2,. of different
microstripline applicators. Discharge tube diameter: 1 mm, pressure: 10 Torr,
feed gas: pure argon, ﬂow rate: 20 sccm.

 

 

 

 

 

900.0 -2” , :
[e 10 Torr
800-0 "- 100 Torr + +
«75‘ 700.0 i‘ 150 Torr
o . o
§ 600.0 2 ‘X200 TOI’I’ + .
[x300Torr X
93‘ 500.0 a. X
2 r o 400 Torr + 0 x
3 400-0 j+500Torr . x E g
._ - “T—* x x .
2;: 300.0 .x x z .
0. 200.0 - x >; t o
x )L o .
100.0 . .. e
l O
0.0 -
0.0 5.0 10.0 15.0 20.0 25.0
Pabs (Watts)

Figure 4.13 Discharge power density variations at different P2,. for argon

discharges created using microstripline system #1. Flow rate: 20 sccm, discharge
tube size: 1 mm.

41

600.0

 

 

 

 

 

 

500.0 -— ’
”E 4000
S o
.é‘
2 300.0 ~ ,3 3‘
0 . K
e at
6 2000 R o 2 sccm I
0. ° ‘
Cl 10 sccm
100.0 - . [it A 20 sccm .
UK ‘3‘ x 40 sccm I
0.0 a T 0 0
0.0 5.0 10.0 15.0 20.0 25.0
Pane (Watts)

Figure 4.14 Discharge power density variations for different P2,. in argon

discharges created using microstripline system #1. Pressure: 10 Torr, discharge
tube size: 1mm.

 

 

 

 

 

 

350
300 . 9
"£2004
0
£200
g 0 o1mmi
O 150 I2mm‘
a3
5 100 ‘ Q
0..
E I I ' '
O r . r r
0 5 10 15 20 25
Pabs (Watts)

Figure 4.15 Discharge volume variations for different Pam in argon discharges

created using microstripline system #1. Pressure: 10 Torr, ﬂow rate: 20 sccm.

42

350

 

 

 

 

 

 

,. 70030"

300 x IAr-H2 l
A A AHydmgen
g: 250 V ‘X ilﬂrogen l
E 200 ‘ X
2 AX
3 150 . .
a; x I ' I
g 100 ~ .
[L I

50 -

o 9 ’
. . O O O
o ’ 0 r T
0 5 10 15 20 25
Pabs (WaﬁS)

Figure 4.16 Discharge power density variations for different P». for Ar, Af—Hz
(95%-5%), H2, and N2 created using microstripline system #1. Pressure: 5 Torr,
discharge tube size: 2 mm.

From ﬁgure 4.10 and 4.11 it is seen that the power density of argon
plasma, created using system #2, decreases as the absorbed power increases
up to 6 Watts. Power density decreases because the discharge length expands
rapidly. However, as the power becomes greater than 6 Watts, the power density
increases with Pm. Power density at higher pressure is higher than the lower
pressure discharges but the proﬁle is similar.

A linear proﬁle of power density versus Pm can be obtained from system
#1, as shown in ﬁgure 4.12. Figure 4.13 also shows, for system #1, that the
power density increases as both the absorbed power and pressure increase. Low

Pam data for high pressure discharges are not available due to the ignition

constraint explained in section 4.2.

43

Figure 4.14 shows that when the ﬂow rate of the gas through the system
was varied with the other parameters held constant, a slight increase in
discharge power density was observed with decreasing ﬂow rate in the range 10
— 4O sccm. However, at 2 sccm, the discharge power density was noticeably
bigger compared to the higher ﬂow rates.

Figure 4.15 shows a comparison of power density for system #1 between
1 mm tube and 2 mm tube. Power density increases faster versus P3,. in 1 mm
discharges.

Figure 4.16 shows that increase in the absorbed power for hydrogen,
nitrogen, and a mixture of hydrogen - argon plasmas generates higher power
density discharges. However, for argon plasma, the absorbed power is used to

expand its volume rather than increase the power density.

4.6 Discharge branch and loop

The discharge tubes were modiﬁed in two ways in order to study the
behavior of argon discharges as they expand. The ﬁrst modiﬁcation involved
creating a branch on the 2 mm quartz tube as shown in ﬁgure 4.17. The main line
of the discharge tube was connected to the argon gas flow meter and the
vacuum chamber using a setup similar to that mentioned in chapter 3. The end of
the branch line was terminated using epoxy. The branching point should be kept
as close as possible to the copper stripline so that the discharge expansion can
reach over it. With enough absorbed power, branching of the argon discharge
can be made. The distance between the branching node and the end of the

discharge in the branching line (B in ﬁgure 4.3) was shorter than the main line

44

discharge (A in ﬁgure 4.3). This may have happened because the pressure in the

branching line is relatively higher than in the main line.

 

 
 
  
   
  
  

 

 

 

Microwave
Energy Input
Branch line
69 . . . 255:3}:553: EB
Mrcrostnplrne 333333;
3353535353333 T-shape 2 mm

Dielectric "”3'3jE'E’E i.d. hollow
Layer 5353535353535 discharge tube

 

 

 

 

 

 

 

   

 

 

Plasma Egg-3:33; Main line Gas FIOM
Drscha rge :3;3;3;3;3;3;
GB Terminated with {351153. EB

 

a variable length E0

stub tuner ———>
Figure 4.17 Top view of argon discharge branching inside the 2 mm id. quartz
tube.

The other modiﬁcation involved creating an oval loop circling the
microstripline as shown in ﬁgure 4.18 and 4.19. At low microwave power, the
argon plasma was generated underneath the microstripline and partially ﬁlled the
oval shape of the discharge tube. Two independent discharges existed in each
section of the tube that passed under the stripline. As the power increased, the
discharge ﬁlled up the volume inside the oval. The oval tube could not be ﬁlled up
completely as there was a gap at the top of the oval discharge that could not be

eliminated with a high microwave power. This gap is believed to be caused by

two surface waves meeting and reﬂecting at the gap. All of these experiments

45

were performed at 1 Torr pressure because the volume of argon plasma is larger

at low pressure.

Microwave '
Energy Input

      
  
  
 
   
 
    

 

 

EB

Spiral shape 2
mm id. hollow

/ discharge tube

Gas Flow

Microstripline

 

Dielectric
Layer

 

 

 

 

> .

 

 

 

 

~1 cm

 

 

(a) I r‘

 

Figure 4.19 Side view of argon discharge inside a loop of 2 mm id quartz tube.
At low Pm, discharge does not completely ﬁll up the loop (a); at high Pm, argon
discharge ﬁlls the loop completely (b) with the exception of a small gap on the top
of the oval.

46

In conclusion, argon discharges created using a microstripline coupling
structure will, with enough microwave power, have the behavior of expand their
volume. The expansion follows the behavior of a fluid. An anomaly from a ﬂuid
behavior occurred when two discharges are placed closed to one another as
shown in ﬁgure 4.19.

Another interesting phenomenon was observed for argon discharges in
the microstripline system #2 at atmospheric pressure. With a proper adjustment
of the variable stub tuning, ﬁlament-like discharges can be created using argon
feed gas at atmospheric pressure. Different input powers, ranging from 5 - 20

Watts, generated different numbers of ﬁlaments, ranging from 1 - 14 ﬁlaments.

 

 

 

 

 

 

 

 

 

 

 

 

 
 
   

 

Microwave v
Energy Input
69 — EB
35325332523253
Dielectric 35353535353533 2 mm id. hollow
Layer 5333333335353E§\ discharge tube
<— ii'iiijii'fi \: «—
Filaments inside Microstripline Gas Flow
discharge tube
G9 Terminated with 353.3"33 EB

 

 

 

 

a variable length
stub tuner ——>

Figure 4.20 Filament-like discharges observed for argon feed gas at atmospheric
pressure.

47

4.7 Conclusion

A series of experiments to determine the discharge volume and power
density have been demonstrated. Both microstripline coupling structure designs
were capable of generating Ar, H2, N2, and a mixture of Af-Nz plasmas. However,
for molecular gases, there are some limiting factors in generating stable
discharges. Pure molecular gas discharges were difﬁcult to generate at
pressures higher than 20 Torr. Moreover, the plasma length (volume) for these
gases was very small compared to argon discharge.

The surface wave excited plasma behaviors were examined by modifying

the discharge tube. Branching and looping of the discharge tube are possible.

48

Chapter 5
Investigation Using Optical Emission Spectroscopy

5.1 Introduction

This chapter describes the plasma discharge diagnostics using Optical
Emission Spectroscopy (OES). The advantage of using OES diagnostic is that
the measurement is done without perturbing the discharge. Gas temperature and
electron density of the discharge can be obtained using this diagnostic method.
Discharges used in this study are the homonuclear diatomic molecules hydrogen
and nitrogen. The gas temperature measurements are explained in section 5.2
whereas the electron density measurements made by investigating the Stark

broadening of hydrogen are explained in section 5.3.

5.2 Gas temperature

5.2.1 Gas temperature measurement theory

The total energy of a given state of a diatomic molecule is given by the
formula (in wave number units)

T=Telc+Ttr+G+F (5.1)
where Talc is the electronic energy, Tr, is the translational energy, G is vibrational
energy, and F is rotational energy. In general, F is a small number since the
energy separation between rotational levels in a given vibrational and electronic
state are typically small compared with the thermal translational energy. Nearly

all gas kinetic collisions produce a change in the rotational quantum number,

49

whereas collisions producing a change in the vibrational or electronic quantum
numbers usually occur much less frequently. Consequently, the relative rotational
population distribution in a sufﬁciently long-lived vibrational state has a
Boltzmann distribution and the rotational temperature reﬂects the gas kinetic
temperature [15].

Further, breaking down these different forms of energy in equation 5.1, the

rotational energy F in a given vibrational level is given by [14]

F = BvJ(J + 1)— DvJ2(J+ 1)2 +... (5.4)
where J is the rotational quantum number, 8., is the rigid rotator rotational
spacing, and 0., is the ﬁrst anhannonic correction to the rotational spacing. In

addition, there are nonrigid rotator corrections to both Bv and DV. These

corrections are given by

RV = Be —ae(v+%)+m (5.5)
and
Dv = De +ﬂe(v+%)+'” . (5'6)

where v is the vibrational state, B, and D1, are constants that corresponds to the
equilibrium separation, a, and ,6,9 are the ﬁrst anhannonic corrections. Values for

those constants that correspond to the experiments are listed in table 5.1.

Table 5.1 Rotational constants for the electronic states of hydrogen and nitrogen

State Be (19 De (ch) Be
H2 (612;) 28.4
N2 (c311,) 1.8259 0.0197 1.0955

 

 

 

 

 

 

 

 

 

 

50

Based on the selection rule, the upper and lower state may have different
electronic angular momentum A. Thus, two or three series of lines (branches)
may appear which are the P, Q, and R branches. lf A=0 in both upper and lower
electronic states, the transition with AJ=0 is forbidden, hence only AJ= _+_1 are
allowed. The AJ=+1 transition gives rise to the R branch and AJ= -1 transition
gives rise to the P branch. The electronic transitions involved in the experiments
for both hydrogen and nitrogen rotational temperature measurements have AA=O,
thus the Q branch is not present. However, it is possible to pick an electronic
transition which has a different angular momentum to observe all the branches; P,
R, and Q. A simple representation of vibrational and rotational energy levels
including the transitions which give rise to the P, Q, and R branches are shown in

ﬁgure 5.1.

51

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0 E
a: .
.C I
O
C
E
AAAA m
A \
D‘s/3&0 O @365; J‘
MMMMM mini“ 8
7
6
5 v“
1
)0. z

 

Figure 5.1 An example of vibrational and rotational energy levels with a number
of transitions in the P, Q, and R Branches.

The relative rotational line intensities I of a Boltzmann distribution are

described by [8]

 

vaJ'(J'+1)hc (5 7)
101', '

I = KV4SJ'J" 0000(—
where K is a constant for all lines originating from the same electronic and
vibrational level, v is the frequency of the radiation, 8);,» is the appropriate Honl-
London factor, 8.,» is the molecular rotational constant for the upper vibrational

level, J is the rotational quantum number, h is the Planck’s constant, c is the

speed of light, k is the Boltzmann’s constant and T, is the rotational temperature.

52

Quantum numbers associated with the upper energy level are denoted with a
prime, and those corresponding to the lower level with a double prime.

Honl-London factor describes the line strength of rotational spectra that
depends on J. The Honl-London formulae for emission of the AA=0, R-branch is
described by [Herzberg]:

__ (J '+A' )(J '—A')
_ J'

S (5-3)

 

where J’ is the rotational quantum number of the upper level state and A” is the
electronic angular momentum of the upper level state. In most emission cases

this factor can be simpliﬁed to S=J+1 from the approximation of equation 5.8.

5.2.2 Gas temperature of H2

5.2.2.1 Experiment procedure

Several OES experiments, using the spectrometer apparatus setup
described in chapter 3, were performed to obtain the rotational temperature of
hydrogen discharges. The feed gases used in the experiments were pure H2 and
a mixture of H2 and Ar. The parameters that were varied include the input power,
pressure, and the ratio of the feed gasses ﬂow rates.

The rotational temperature for hydrogen discharge was determined using
the R branch of the G‘z;—> 5‘2; (04)) band of H2 molecule, where 6‘2; is
the upper electronic level and B12“+ is the lower electronic level of the 0
vibrational quantum number. Eleven emission lines (R0 — R10) in the spectrum

range of 4530 A — 4650 A were identiﬁed as shown in ﬁgure 5.2.

53

 

 

 

 

 

 

 

 

 

l
9 l
5
3 R233 I
g: 7'
§ R° '
E .
.5 Re Rs
.3 R10
5 R7
_ -_- vlJ
4530 4550 3 4570 4590 4610 4630 4650
Wavelength (A)

Figure 5.2 Emission spectra of the R Branch of the G122," —> 3120* (0-0) band

of H2 molecule.

It is found that the plot of In(I/S) for this band is a linear function of the

upper rotational energy under a variety of conditions, except for the R5 and R9

components [8]. Those lines usually are perturbed by nearby upper energy levels

that have different lifetimes. In the Boltzmann plot, I is the intensity of the line and

S is the corresponding HonI-London factor. The R1, R2, R3, R4 lines were not

included in calculation since they were not resolved.

Table 5.2 Energy Level for the R branch of the G12;—> B123“+ (0—0) band of H2

 

 

 

 

 

 

 

 

 

 

 

 

molecule.
. . Relative upper
Eggtlonal XX)avelength level1 energy S
(crH' )

R0 4627.5 292.86 60.01
R5 4624.7 895.24 86.17
R6 4618.4 1150 315.83
R7 4598.1 1490.48 1 13.09
R8 4581.3 1835.71 356.69
R9 4557.4 2238.1 199.34
R10 4537.9 2666.67 642.39

 

 

54

Table 5.2 shows the upper energy level of the R—branch rotational lines
and the corresponding value of S, the Honl-London factor. The intensity (I) was
obtained from the peak intensity of the line subtracted by the average noise. The
value of In(I/S) was calculated and plotted against the upper level energy, as

shown in ﬁgure 5.3. The line of best ﬁt was obtained for the plot. The slope of this

line corresponds to-—hy—f-, where c is the speed of light. From the value of the
r

slope, the rotational temperature of H2 is obtained.

 

ln(|IS)
do

 

 

 

 

5 r 0 0
0 500 1000 1500 2000 2500 3000

Relatlve upper level energy (cm")
Figure 5.3 Boltzmann plot for the lines R0 and R5 - R10 of H2 plasma.

The data shown in ﬁgure 5.3 was for a H2 plasma operated at 0.5 Torr

pressure, 3 sccm ﬂow rate, and 33 W microwave incident power.

55

5.2.2.2 Experimental results

The experiment results for the hydrogen rotational temperature are
presented below. The accuracy of rotational temperature, determined using this
method, is found to be within 1 100 K. This is estimated from the reproducibility
of the data obtained.

When the ﬂow rate of the gas was varied with the other parameters held
constant, a slight increase in the rotational temperature of pure hydrogen
discharge was observed with increasing ﬂow rate.

The presence of argon cools down the discharge as can be seen in ﬁgure
5.5. The higher percentage of argon gas fed into the discharge, the lower
rotational temperature of H2 measured.

Figure 5.6 shows that the rotational temperature of hydrogen has little

variation for different pressures from 0.5 to 5 Torr.

 

 

 

 

 

 

 

0 0.5 1 1.5 2 2.5 3 3.5

Flow rates (sccm)

Figure 5.4 Variation of rotational temperature of H2 with ﬂow rates for pure H2
plasma. Pressure: 0.5 Torr, Pine: 33 W.

56

 

1350
1300 4
1250 3
1200 3
1150 3
1100 -
1050 ~

Temperature (K)

55

 

 

to
8

 

0 1 2 3 4 5 6 7
Flow rate (eccm)

Figure 5.5 Variation of rotational temperature of H2 with different Ar ﬂow rates in
H2 - Ar plasma. Pressure 0.5 Torr, Pine: 33 W, H2 ﬂow rate: 2 sccm.

1400
1350 4
1300 J
1250 .
1200 +
1150 ~
1100 «
1050 ~
1000 ~
950 «
900

 

Temperature (K)

 

 

 

0 1 2 3 4 5 6
Pressure (Torr)

Figure 5.6 Variation of rotational temperature of H2 with different pressure for H2
plasma. Pine: 33 W, H2 ﬂow rate: 2 sccm.

5.2.3 Gas temperature of N2
5.2.3.1 Experiment procedure

Several OES experiments, using the spectrometer apparatus setup
described in chapter 3, were performed to get the rotational temperature of
nitrogen discharges. The feed gases used in the experiments were pure N2 and a
mixture of N2 and Ar. The parameters that were varied include the input power,

pressure, and the ratio of the feed gasses ﬂow rates.

57

The nitrogen discharges created in the microstripline plasma source were
assumed to be weakly ionized. Thus, the rotational temperature measurements
were performed by analyzing the spectrum of the neutral species. The emission
band system for nitrogen commonly known as the Second Positive System
(SPS) in nitrogen spectra was used to determine the rotational temperature. The
SPS describes the energy level transition from C‘°’1’Iu to Bang. A wide spectral
scan from 3730 A — 4000 A as seen in ﬁgure 5.3 conﬁrmed that the SPS

emission from the nitrogen discharge was detected.

 

(3,1) (2.0)

(5,2) (4'1)

 

 

 

(6.3)

2.4) -..l .. J J

3730 3750 3770 3790 3810 3830 3850 3870 3890 3910 3930 3950 3970 3990
Wavelength (A)

Figure 5.7 Spectrum of nitrogen discharge showing the band heads of the SPS
system.

Intensity (arb. units)

        

 

During the wide spectrum scanning experiment, the strongest signal
intensity detected by the spectrometer was the (2,0) band-head vibrational
transition. Moreover, the ﬁne structures of the rotational lines in that particular

band-head were visibly shown. Hence, those rotational lines were used in

58

determining the gas temperature. Figure 5.4 shows the detail of the R and P
branches of the (2, 0) transition in the SPS system. Eleven emission lines (R20 -
R30) in the spectrum range of 3758 A - 3783 A were identiﬁed. Conversely, the
lower J values of the R branch emissions were not resolved since they coincided

with the P branch emissions.

 

 

 

 

 

 

 

.33

c

:l

“E

3

E"

a

c

8

.E l

8 l

'5 R21 l

E R23 R20 l 3

u" l . R25 R221 ' A: i l
R29 7 R26 R24 ' ' { i ll!

 

800le0 , . ..

 

 

 

T r

3753 3758 3763 3768 3773 3778 3783 3788 3793 3798 3803
Wavelength (A)

Figure 5.8 Fine structures of the (2,0) SPS system of nitrogen discharge that
were used for rotational temperature measurement.

59

 

Table 5.3 Energy Level for the R branch of the (2,0) SPS system of nitrogen

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

discharge.
. Relative upper
Rotatlonal Wavelength
Line (A) level1 energy
(cm )
R20 3780.44 837.76 19.8
R21 3778.58 917.42 20.80952
R22 3776.66 1000.67 21.81818
R23 3774.68 1087.51 22.82609
R24 3772.64 1 177.95 23.83333
R25 3770.53 1271.97 24.84
R26 3768.37 1369.57 25.84615
R27 3766.14 1470.76 26.85185
R28 3763.86 1575.51 27.85714
R29 3761.51 1683.84 28.86207
R30 3759.1 1 1795.74 29.86667
0
-0.5
-1 .3
<1?
25'
-1 .5 5
-2
-2.5 .3 . , L
700 900 1 100 1 300 1 500 1700 1900

Relative upper level energy (cm")
Figure 5.9 Boltzmann plot for the lines R20 - R30 of N2 plasma.

The data shown in ﬁgure 5.9 was for a mixture of Ar - N2 plasma operated
at 5 Torr pressure, 2 sccm ﬂow rate for both feed gases, and 33 W microwave

incident power.

60

5.2.3.2 Experimental results

The experimental results for the nitrogen rotational temperature are
presented below. The accuracy of rotational temperature, determined using this
method, is found to be within 1 100 K. This is estimated from the reproducibility
of the data obtained.

From ﬁgure 5.10, it can be seen that the rotational temperature of Ar - N2
plasma slightly increases versus pressure from 0.5 - 10 Torr. The temperature
ranges from 1025 - 1150 K. From ﬁgures 5.11 and 5.12, it can be observed that
the rotational temperature of N2 increases with the increase of Ar flow rate. Thus,
the Ar - N2 mixture has a higher rotational temperature than that of pure N2
plasma discharges. The rotational temperature of pure N2 discharges in the

pressure ranges from 0.5 -— 5 Torr are less than 750 K.

 

1300
1250
1200
11500 .3
1100 5
1050 - e 9

0... l
9503 .-

 

 

Temperature (K)

 

 

850
800

 

 

 

0 2 4 6 8 10 12
Pressure (Torr)

Figure 5.10 Variation of rotational temperature of N2 with different pressure for N2
- Ar (10% - 90%) plasma. Pine: 33 W, ﬂow rate: N2-2 sccm, Ar-18 sccm.

61

 

1200

 

1100

5

800 4

Temperature (K)

7001

 

 

 

-5 o 5 10 15 , 20
Flow rate (sccm)

Figure 5.11 Variation of rotational temperature of N2 with different Ar flow rates in
N2 — Ar plasma. Pressure 0.5 Torr, Pine: 33 W, N2 ﬂow rate: 2 sccm.

 

 

 

 

 

 

 

 

1300
12005
A1100~ {{ 3
391003
2
B 900
It?
a. 8005
E 700 .
'- 6000 'e90%Argon
I50%Argon
500” k‘PureN2
0 2 4 6 8 10 12

Pressure (Torr)

Figure 5.12 Variation of rotational temperature of N2 with different pressure for
pure N2, and mixtures of Ar - N2 (50% Ar, and 90% Ar) discharges.

62

 

5.3 Stark Broadening

There are many line broadening mechanisms in the optical light emission
from a plasma. The two dominant mechanisms are the Doppler broadening and
the pressure broadening. Pressure broadening exists in dense plasmas where
line shapes are strongly inﬂuenced by interactions of the radiating atoms or ions
with the surrounding particles. From the physical point of view, pressure
broadening can be further subdivided into resonance, Van der Waals, and Stark
broadening. In a plasma with ions and electrons present with sufﬁciently high
concentrations (>1013 cm‘3), the dominant pressure broadening mechanism is the
Stark broadening. Stark broadening of spectral lines can be used to determine
the electron density of a discharge. This leaves Doppler broadening as the most
likely competing mechanism, which must be considered along with the apparatus
broadening.

The electron density of the discharge, created using microstripline
coupling structure #1, was determined by examining the Stark effect using OES.
The emissions of the hydrogen Balmer l3 and 8 transitions (H5, H5) from a mixture
of Ar — H2 plasma were analyzed. Those lines were chosen because they have
sufﬁciently well known Stark proﬁles and are favorable to measure electron
density in the range 1013 -— 1017 cm’3.

Purely Stark broadened lines of the hydrogen Balmer series have been

computed by Griem [18]. Griem has determined the width of the Stark broadened

63

 

Balmer lines as a function of plasma electron density at various electron

temperatures. For an electron temperature of 5000 K the plasma density is given

by:

n = [(3.99x108)(M%):IA cm'3 (5.9)

where A703 is the Full Width Half—Maximum (FWHM) of the purely Stark
broadened line in Angstroms and or is a coefﬁcient for the various Balmer lines.
King [15] summarized the a coefﬁcients along with the useful density range as
given in table 5.4.

Table 5.4 Coefﬁcient a for. electron density estimates and the ﬁne structure
splitting for H3 and H5 lines ofﬂdrggen Balmer series.

 

 

 

 

 

 

 

 

(1 Density A203
H2486.1 nm 0.0762 ~10“ cm’3 0.077 A
Hg 410.1 nm 0.149 ~1013 cm’3 0.057 A

 

FWHM of the purely Stark broadened line can be deduced from the

experimentally observed line by using the following:

 

Ms 45100.02 -Mf02 All-0002 (5.10)
where A192,, is the FWHM of the observed line, A2143 is the ﬁne structure splitting,
and MM is the apparatus and Doppler broadening.

Apparatus broadening along with Doppler broadening was estimated by
measuring an argon line at 411.9 nm in a low pressure discharge. Since the only

signiﬁcant broadening at this low pressure is expected to be Doppler broadening

which is small for Argon. The observed width in the argon emission was

 

assumed to be purely instrumental in origin. Almfor this experiment has FWHM

of 0.3 A.

The lines presented in ﬁgure 5.13 and 5.14 are the H5 and H5 emission

lines from a mixture of Ar - H2 plasma operated at 1 Torr pressure, 27.5 sccm

ﬂow rate for argon gas, 1.5 sccm ﬂow rate for hydrogen gas, and 26.7 W

microwave absorbed power.

 

 

 

 

- o
e
.13 o
= e
8
3
a?
3 . e
8 7 e
5 e
. e
e
0
WW... 0 .°!M9W
4859 4859.5 4860 4860.5 4861 4861.5 4862 4862.5 4863
Wavelengths(A)

Figure 5.13 The observed broadened H3 hydrogen Balmer line.

65

 

 

 

 

e
e
E o 0
c 1
=5 e
e
3 O
E
5 . ’
o
5 e
o. o .0 0 e
3 e. O 9 O O
O 00 90
e co 0
. .9000 ’ ”” ”00‘
4099 4099.5 4100 4100.5 4101 4101.5 4102 4102.5 4103
Wavelengths (A)

Figure 5.14 The observed broadened H2, hydrogen Balmer line

The plasma density was determined to be 6.6x1013 cm'3 and 3.5x1013 cm‘3

from Stark broadened H0 and H5 measurements respectively. A similar procedure

for plasma density measurements was performed on discharge at 100 Torr

pressure. The results are listed in table 5.5.

Table 5.5 Measured plasma density from Stark broadened H3 and H5Iines of

 

 

 

 

 

hydrogen.
Pressure (Torr) Plasma density (cm'3)
H3 1 8.8x1o13
H3 100 1.4x10W
H0 1 3.5x10“r
H8 100 7.1x1o13

 

 

 

 

 

66

5.4 Conclusion

The rotational temperature of H2, Ar — H2, N2, and Ar - N2 microwave
plasma discharges were measured. The results showed that increase in pressure
slightly increases the temperature. The variation in the gas temperature with
argon concentration was of the particular interest, since the global analytical
model, discussed in chapter 7, is based on argon discharge. The rotational
temperature of Ar — H2 and Ar — N2 discharges, with argon as the dominant
species, are around 1000 K. This value will be applied in the global analytical
model.

The observation of the Stark broadened H3 and H5 lines of 1 Torr Ar — H2
discharge shows that the discharge’s electron density was on the order of 1013

cm'3. This result will be compared to the result from the global model in chapter 7.

67

Chapter 6
Investigation Using Langmuir Probe

6.1 Introduction and brief review of the Langmuir probe diagnostic

Langmuir Probe diagnostics measures the current — voltage (l-V)
characteristics of a discharge. From the I-V characteristics, the electron
temperature and the charge density can be determined. In the double Langmuir
probes (DLP) diagnostic, two metal probes are inserted into the discharge and a
bias voltage is applied across the probes to draw electron and ion current. The
bias voltage will draw positive ion current to the negative probe and electron
current to the positive probe. As the bias voltage becomes very large, the more
negative probe essentially draws the ion saturation current, which is balanced by
the net electron current to the other probe. For DLP diagnostics, a Maxwellian
electron energy distribution is assumed. Further, the double probe method
collects information on the high-energy tail of the electron energy distribution.

In this research, DLP were chosen over single Langmuir probe diagnostic
since there was no well-deﬁned ground electrode in the discharge. A typical l-V
characteristic obtained from a DLP measurement is shown in ﬁgure 6.1. The l-V

characteristic is governed by the following equation [16]:

1+]
l=ﬁl—ex 1, V=V1-V2 (6.1)
12 —1 A2 Te

 

where I1 and I2 are the ion currents to probe 1 and 2 respectively, A, and A2 are

the collection areas, V1 and V2 are the probe potentials with respect to the

68

plasma potential, and T, is the electron temperature. If A1 = A2, then I, = I2 = I,-,

then equation can be simpliﬁed to:

V
1 = 1,- tanhE—Tg] (5-2)

--------- [2

 

<W

I1 ........ 1---l uuuuuuuu

Figure 6.1 Typical current — voltage (l-V) characteristic.

 

The electron and ion density can be found using [Lieberman]:
1; =ens uBA (6-3)
where e is the elementary charge, ns 5 0.61 no is the sheath edge density, us is

the Bohm velocity, and A is the collection area of the probe. The Bohm velocity

us is given by:

(6.4)

02, V2
"Fl—J

M

where M is the mass of the ion.

69

 

The discharge in the DLP diagnostic is assumed to be collisionless. Thus,
the simple case of the probe theory, that in which the collisions and magnetic
ﬁelds are negligible, is used. Collisionless discharge can be achieved when the
mean free path of the ion (21,) is longer than the discharge sheath thickness (3).
The mean free path of ion in argon discharge is deﬁned as [13]:

1
,i- =—-—— cm 6.5
1 mp ( )

where p is the pressure in Torr, and the ion is assumed to have a low-energy (T 3
~ 0.05 eV). The sheath thickness as explained in section 3.5.1 is on the order of
a few microns.

When the sheath is thick compared with the probe radius, the current is
limited by the orbital motion [19]. Thus, the probe characteristic appears as
shown in Figure 6.2 follows for different probe shapes. However, in this
experiment, the probe radius is much bigger than the sheath thickness; therefore,

the saturation region follows that of the planar probe.

70

Sphere
J0

Cylinder

 

Plane

 

 

V

Figure 6.2 Theoretical shape of the saturation current portion of the probe
characteristic for various probe shapes when the probe is limited by orbital
motions.

6.2 Experimental setup

DLP diagnostics were done for pure argon discharges at pressure ranges
from 3 to 10 Torr. The ﬂow rate of the argon feed gas was set to 10 sccm. The
microwave power absorbed by the discharges measured was 2 Watts. For the
equipment setup detail for this diagnostic, please refer to section 3.5.

The DLP diagnostics at each pressure point were conducted three times
in order to check the consistency of the probes performance. As can be seen in
ﬁgure 6.3, the l-V characteristics have an excellent repeatability, with the
exception of a few minor discrepancies in the saturation regions. Also, the
average values of the saturation current in the saturation region 1 and in the
saturation region 2 were slightly different. This shows that Probe 1 tends to draw

a bigger ion current. This may happen due to fact that the collection area of

71

 

probe 1 was a few tenths of a micron longer than the collection area of probe 2.
To verify this, the probes’ connections to the multi-meter were switched. The
result, as seen in ﬁgure 6.3, was that after the probe was switched, the average 3
of the saturation current in region 2 was larger than in region 1. Hence, this

proves that the probes used in the diagnostics were not exactly identical.

0.6

 

0.4

 

.0
N

 

 

Currents (mA)
0

 

 

 

 

 

 

'02 Sid—al.?" * l
a Trial 2
‘0-4 ATrial 3 .
xProbes Switchedj
-0.6
-60 4o -20 o 20 40 60

Volts (V)

Figure 6.3 l-V curves obtained using DLP diagnostic. Pressure: 10 Torr, Pm:
2.34 Watts, Gas: Argon, ﬂow rate: 10 sccm.

The l-V curves obtained from the DLP measurement have a similar shape
to the hyperbolic tangent function described in equation 6.2. Since the saturation
ion current was different for each probe, equation 6.1 was used. Re—arranging

equation 6.1 into the following form:

72

[+11

2 ’1 = 1 (8.6)

I
A1 T
A2 8

the I, and I2 values were obtained by averaging the saturation current for each

 

probe with assumption that the saturation regions were ﬂat line. A1/A2 is
proportional with the ratio of I, and I2 according to the equation 6.3.

A log plot from equation 6.5 can determine the electron temperature,
which is the inverse of the slope. The data points used to generate the log plot

were the ones between the two saturation regions.

 

-2 l- _ ___

 

GANG-F
_L__

y = 0.4653x + 0.495

— 7 _ l

   

 

 

'___—”l

[ e 7P=5 Torr“

l5- Linear (P35 Torr)i

 

 

 

 

-5
-10 -5 0 5 10
Volt (V)

Figure 6.4 Log plot of the l-V characteristic from DLP diagnostic. C=l+l1ll2-l,
A=A1IA2.

73

6.3 Results and discussions

The results of DLP diagnostic for argon discharge are presented below.
As can be seen in ﬁgure 6.5, the electron temperature decreases as the pressure

increases. The electron temperature ranges from 2.3 eV — 1.9 eV.

 

2.7

O

 

 

 

1.7 - i . r
0 2 4 6 8 10 12

Pressure (Torr)
Figure 6.5 Variations of electron temperature for different pressures. Gas: Argon,

ﬂow rate: 10 sccm, Pm: 2.34 Watts, Discharge tube size: 2 mm, Microstripline
structure #1.

The charge densities of argon discharges as shown in ﬁgure 6.6 were
measured to be 3 — 6x1012 cm'3. As the pressure increases, the charge density
increases. The results from electron temperature and charge density

measurements conﬁrmed that the assumed sheath thickness, explained in

section 3.5, is valid.

74

 

1.0E+13
9.0E+12 5
8.0E+12 ~
7.0E+12 .
6.0E+12 5
5.0E+12 5
4.0E+12 -
3.0E+12 ~
2.0E+12 .
1.0E+12 5
0.0E+00 l , ,

0 2 4 6 8 10 12

Pressure (Torr)

Figure 6.6 Variation of charge density for different pressures. Gas: Argon, ﬂow
rate: 10 sccm, Pm: 2.34 Watts, Discharge tube size: 2mm, Microstripline
structure #1.

no (cm'3)

 

 

 

6.4 Conclusion

Experiments to determine the electron temperature and the charge density
of argon discharges using DLP diagnostic were done. The l-V characteristics
obtained from this DLP measurements shows that the geometry of the probe is
large enough compared to the sheath thickness so that the saturation regions is
ﬂat. This means that the Debye length of these discharges is very small, thus, the
density is high.

The results of the electron temperature and charge density measurements
from this DLP diagnostic will be compared to the ones from the global analytical

model of argon discharges in chapter 7.

75

 

Chapter 7

Global Model Calculations

7.1 Introduction

The electron temperature and charge density in a discharge can be
predicted using a Global Model. This chapter describes how the model was built
and compares the results with the experimental results from the previous
chapters. The global model calculations were done for pure argon discharges,

since argon has been use extensively in the experiments.

7.2 Theoretical background

Based on the relation between the pressure and the discharge dimension,
the discharge can be categorized into three regimes. They are:

(a) Low pressure: 41’ 2 (12,!)

(b) lntennediate pressure: (R,l) 2 ,1,- 2 (7% )(RJ)
e

(c) High pressure: 21,- s(% )(RJ)
e

where ,1,- is the mean free path of ion-neutral collisions as explained in chapter 6,
equation 6.5, R is the radius of the discharge tube, 1 is the length of the plasma
obtained from the discharge volume experiments from chapter 4, T,- is the ion
temperature, and To is the electron temperature.

In the experiments, the discharge volume was small. However, the mean

free path of argon ion never exceeds the discharge dimension because the

76

pressures used were higher than 0.5 Torr. Hence, the discharges fall into the
intermediate and high pressure regimes. In addition to that, the discharge has a
cylindrical geometry. Thus, all of the calculations presented here are for cylinder
geometry.

In the intermediate pressure regime, the electron temperature an be
determined from the gas density (n,,) and the effective plasma size (dog) as can
be seen in ﬁgure 7.1. Gas density information was obtained from the pressure

using the Ideal Gas Law:

P
7.1
kB Tg ( l

 

"g:

where p is the discharge pressure, k3 is the Boltzmann constant, and T9 is the
gas temperature. Gas temperature for argon discharge was found to be around
1000 K from the DES experiments.

6 .

 

Te (eV)

 

 

 

1.E+18 1.E+19 1.E+20 1.E+21

"9*deit (m4)
Figure 7.1 T9 versus ng-deﬁ for Maxwellian electrons in argon [13].

77

The effective plasma size as described by Lieberman is

d .1 RI
eﬂ 2Rh1+lhR

(7.2)
where
_ l
, /2
h] z 0.8 3 + — (7.3)
2 4i
and
_l
R A
h R e 0.80[4 + -——] (7-4)
4:
h, and hi; are the density proﬁles for the axial sheath edge and the radial sheath
edge, respectively. They are derived from the diffusion equation.

The estimation of the plasma density (no) can be found using

 

n0 = P000 (7.5)
e u B Aeﬂ 87‘
where
Aeﬂ = 270m h, +1702) (7.6)

P000 is the absorbed power obtained from the discharge volume and power
density experiments, A,” is the effective area, m; is the Bohm velocity, and 87 is
the total energy dissipated per ion lost from the system.

The total energy dissipated per ion lost from the system 81 is the sum of

the collisional energy losses ac, the mean kinetic energy lost, which for

78

Maxwellian electrons is equal to 2 T9, and the mean kinetic energy lost 6). For
argon discharges s,- z 5 .2 Te .

The value for 82 is approximated using ﬁgure 7.2.

 

 

 

 

 

1.E+03 3
’>‘
3% 1.5+02 0
o a
00 .
x
1.E+01 3 44M... , ,.
1 10 100

Te (9V)

Figure 7.2 Collisional energy loss per electron-ion pair created, 6‘0. versus T6 in
argon discharge (compiled by Vahedi, 1993) [16].

In the high pressure regime, the discharge density becomes non-uniform.
The transport is diffusive and the density proﬁle is well described by a Jo Bessel
function variation along the radial axis and a cosine variation along the length of
the discharge. In this regime, the electron temperature can be estimated from the

gas density (rig) and the diffusion length (A) as can be seen in ﬁgure 7.3. Gas

density is obtained using equation 7.1.

79

 

10-

Te (eV)

 

‘—

 

 

T77TTTT T 7 T TTTTY—‘f

 

o ..... 5 -4.--” 32-.-..- ..
1.E+17 1.E+18 1.E+19 1.E+20 1.E+21 1.E+22 1.E+23 1.E+24

ng*A (m'2)
Figure 7.3 T9 versus ng*A for non-uniform argon discharge (compiled by P.Mak,
1994) [ECE989A].

The diffusion length A can be derived from the Helmholtz equation for
diffusion:

v20 + (2)0 = o (7.8)
D

a

where w, is the ionization frequency and D8 is the ambipolar diffusion coefﬁcient.

In cylindrical coordinates and assuming that the discharge is 4) symmetric,
equation 7.8 becomes:

2 2 .
31 15" a”+[K¥-)n=0 (7.9)

+-——+—
6r2 '6' 622 a

80

Using the separation of variables technique n(r,z)= R(r)Z(z) and assuming that

the density is zero at the wall and at the ends of the plasma along its length, the

solution for the differential equation are:
Z (2) = Acos[:lr-z) (7.10)

for the axial solution, and

R(r)=AJO[%r-) (7.11)
and
. 2
__L=[!£Q_l_) {35)2 =22. (7.12)

for the radial solution, where 201 = 2.405 is the ﬁrst zero of the Bessel function,

1
and Da z(T%)/21i “B-
I
The peak charge density for the high pressure regime can be estimated

from the power balance calculation.

ﬂoss =95T c1ri_.‘24"11:i=Pabs (7-13)
A

The total ﬂux in the axial direction is

27rR R ..
Ifends =2 I Fl _1 02 rdrd0=4era£n0 IJ0(!—9—1-r]rdr
0 0 z_/2 I 0 R

~ Jr R2 .
Irends =4”Da ‘1‘"0 —J1(ZOI) (7-14)
101

The total ﬂux in the radial direction is

81

I I
~ /2 2” for /2
Irrad = I Jrlr=er9d2=‘27’—R—Da no J1(201) I
_I 0 ’V
/0 2
~ __ 2301 1 0
[r000 44700 n0 #10001? (7.15)
An equality for Pens and the total ﬂux can be achieved by combining equation
7.14 and equation 7.15 and putting them in the equation 7.13. The peak charge

density can be calculated by re-arranging the power balance equation into the

following form:

 

 

no z P0020 (7.16)
47rDa J1(jm{§07; +1231 ]e£T

where J1 (201% 0.519

7.3 Results and discussions

Using the global model derived above, the electron temperature and
electron density of argon discharge were calculated. From chapter 5, the
hydrogen and nitrogen rotational temperatures of argon dominated discharges
were around 1000K. Thus the gas temperature (T g) for these calculations was
set to 1000 K. However, the rotational temperature slighty increases as the
pressure increases. Hence, the error in calculated value may increase as the
pressure increases. Global model calculations were performed for pressures

lower than 100 Torr.

82

As shown in ﬁgure 7.4, the electron temperature decreases as the
pressure increases, and the trends for both microstripline coupling structures are
similar. As pressure increases, the number of collisions increases. This makes
the electron temperature decrease; because when the electron collides with

heavy species, it losses its energy.

 

 

 

 

10%
91 3.333%li
8 Isystem#2i
71
A 6
>
3 53.
0
l- 43
3,.
2 .7 3
1
o 1 l l'
0 20 40 60 80 100

Pressures (Torr)
Figure 7.4 Comparison of the global model electron temperatures of argon
discharges created in system #1 and system #2.

The measured electron temperatures from DLP diagnostics have slightly
lower values as compared to the global model calculations. However, they both
shows similar trend as seen in ﬁgure 7.5. Aliev [20] remarks for probe diagnostics
is that for surface wave (SW) sustained discharges, the perturbation caused by
probes inside the plasma and the resultant potential inaccuracies are aggravated
by the fact that wave pattern, the basis of plasma maintenance, can be quite
noticeably perturbed even outside the plasma, thus enlarging possible deviations

of the measured plasma parameters from their unperturbed values.

83

 

 

 

 

 

5 _2- 2 __
. reGlobal Model;
4.5— IDLP ,
4 a
9 3.5
3 e
l3 3«
2.5 ’
I I Q
2 ' I I
" e
1.5 l l l 0
0 2 4 6 8 10 12

Pressure (Torr)

Figure 7.5 Comparison of the electron temperatures between the global model
calculations and the results from DLP.

Figures 7.6 — 7.8 show the variation of peak charge densities for different
Pam, pressures, discharge tube sizes, and microstripline coupling structures.
Overall, the charge density increases as the P». increases. However, there are
cut regions at low Pam where the density abruptly increases. Using the global
model, charge density of argon discharges is calculated to be on the order of
1012 —10‘5 cm’3.

In terms of discharge tube sizes, higher peak charge density can be
obtained using a 1 mm discharge tube rather than a 2 mm one. This follows the
ﬁrst criterion of plasma, discussed in chapter 2, that the smaller the dimension of

the system, the higher the density.

84

 

 

 

 

 

1.8E+15
+
1.6E+15 +
+
1.4E+15
+
1.2E+15 +
+
1E+15 0
<3" +
E o
3 o
8
8E+14 - ,—-——-~~«~»--—-1
o - 1 Torr
o x 2 Torr ‘
6E+14 O A 3 TON i
o 5 Torr l
x 10 Torr ]
4E3“ o 50 Torr I
1199.19!)
x
2E+14 + x x x
x
x Ck <> 0 ° 0
o 0
0 5 10 15 20 25
Pabs (watts)

Figure 7.6 Peak charge density of argon discharge created using microstripline
structure #1. Discharge tube size: 2 mm id.

85

 

 

 

 

 

 

 

4.0E+15
Rig—Tar" x
3.5315 1 I 10 Torr
A 25 Torr
x 50 Torr x
3-OE+15 J x 100 Torr
2.5E+15 -- X
«3A
5 2.0E+15 X
8
1.5E+15 a x x
X
X A
1.0E+15 x A
x A
X A
5.0E+14 X A -
x ‘ '
A X I ' O
'3 9 ° ’
0.0E+OO L‘J , I ,
0 5 1O 15 20
Pabs (Watts)

Figure 7.7 Peak charge density of argon discharge created using microstripline
structure #1. Discharge tube size: 1 mm id.

86

 

 

 

 

3.5E+15
if“; X
354-15 ~ {moron I x
1‘25 Torr ‘
ix50 Torr i
2.5E+15 i '35 191?!
x
”A 2E+15
5, x
8 1.5E+15
x x
x
A
1E+15 x X A
x
x x A
5E+14 r A . .
I o
I O
E ' ‘ . O
o 1 ' r V
0 5 10 15 20 25
Pabs (Watts)

Figure 7.8 Peak charge density of argon discharge created using microstripline
structure #2. Discharge tube size: 1 mm id.

87

The performance of both microstripline coupling structures in terms of

power density is very similar, as shown in ﬁgure 7.7 and 7.8.

 

 

 

 

 

 

9E+13

8E+13 - ’

7E+13 ~
A 6E+13 +
'E 5E+13 “ oGlobal Model?
0 o i
E 4E+13 - t-_D_L_Pm_fwj

35+13 ~

0
2E+13 ~ .
1E+13 w 0 I. I I - _ _ _
0 . 1 l l l
0 2 4 6 8 10 12

Pressure (Torr)

Figure 7.9 Comparison of calculated charge density from global model and
measured charge density from DLP diagnostic.

From ﬁgure 7.9 it is seen that the measured charge density is lower than
the calculated value. DLP diagnostic, discussed in chapter 6, measured the
charge density at one end of the discharge. Aliev [20] explains that the axial
density proﬁle for surface wave sustained plasmas in cylindrical geometry has a
linear function versus the axial coordinate z. The charge density is lower at the
extreme 2 compared to the density near the source. The linear axial decrease of
the charge density also depends on frequency, pressure, and discharge radius.
The gradient becomes larger as the frequency increases and/or pressure

increases and/or discharge radius decreases.

88

 

Table 7.1 Comparison of the charge density calculated using global model and
measured from the Stark effect
I Global model H5 H5

Charge density I 1.4x1013 cm‘3 6.6x10"3 cm'3 3.5x1013 cm'3

 

 

 

 

 

 

 

Table 7.1 shows a comparison between calculated charge density from
global model and the measured charge density from the Stark effect using OES.
The densities are around 1013 cm‘3. Minor differences between the calculated
and the measured value arise because the charge Stark effect phenomenon was
observed from a mixture of Ar - H2 discharge. Meanwhile, the global model

calculations were based on pure argon discharges.

89

Chapter 8

Summary and Recommendations

8.1 Summary of Results

Two designs of a miniature microwave plasma source using microstripline
technology have been developed. The plasma sources were able to create
cylindrical discharges inside quartz tubes with 1 - 2 mm radii. The volume of the
discharge increases as the power is increased. Discharge absorbed power
densities varied from a few 10’s W/cm3 to over 700 chm3 as pressure was
increased and discharge tube size was decreased. The plasma sources can
create pure argon discharges at atmospheric pressure with as low as 5 W of
absorbed power. At atmospheric pressure, ﬁlament-like argon discharge can be
generated.

At very low power, microstripline applicators generate the discharge in a
similar fashion as the parallel plate reactors. However, with increasing power, a
plasma surface wave (SW) discharge exists along a tube that extends
perpendicular to the stripline. The behaviors of this SW sustained plasma were
examined. Discharges can be divided by creating a branched tube.

Characteristics of the discharge were measured using optical emission
spectroscopy and the double Langmuir probe. Using OES, the gas temperature
of argon discharges was approximated to be around 1000 K for the pressure
range from 1 - 10 Torr. As the pressure increased, gas temperature of the

discharge slightly increased. The addition of more Ar in a mixture of Ar -— H2

90

discharge decreased the gas temperature. However, the addition of Ar in a
mixture of Ar - N2 discharge increased the temperature. The charge density was
measured by observing the Stark broadened H, and H3 lines of hydrogen in a
mixture of Ar — H2 discharge at 1 and 100 Torr. The charge density was on the
order of 1013 cm'3 - 1014 cm'3.

The charge density was also measured using the DLP diagnostic. The
probes were inserted at the end of the discharge. From this measurement, the
charge densities of argon plasmas for a pressure range form 3 - 10 Torr were
1012 — 1013 cm'3. Discrepancies in the charge density measurement using DES
and DLP occurred because of the linear decrease of the axial density proﬁle for
SW sustained plasmas. Speciﬁcally, OES measures the average density and
DLP measures the density at the edge of the cylindrical discharge. Using DLP,
the ebctron temperature of a pure argon discharge was observed to decrease as
the discharge pressure increased. The electron temperature for argon plasmas in
that pressure range were 1.8 - 2.3 eV.

The global analytical model was used to calculate the density and electron
temperature for pure argon plasmas, which were created using microstripline
coupling structures. The model was calculated based on the measured discharge
volume, absorbed power, pressure, and gas temperature. From the global model,
the electron temperature and peak charge density of the discharge were
obtained. The calculated values of these fundamental plasma parameters
roughly matched with the measured values from DES and the DLP diagnostic

with only minor differences.

91

With the knowledge of the fundamental characteristics of the discharge,
plasma validity can be checked from the plasma criteria explained in chapter 2.
For a pure argon discharge inside a 2 mm tube with 5 Torr pressure, the electron
temperature (T e) is 2.3 eV, gas temperature (T 9) is 1000 K, and electron density
(n3) is 6x1013 cm'3. Using equation 2.2, the Debye length (Ad) is found to be
1.45x10“ cm. This proves that the discharge fulﬁlls the ﬁrst criterion of a plasma.
Following the ﬁnding of M, the second plasma criterion can also be fulﬁlled. N, in
this case is around 773.

The third criterion deals with the plasma oscillation frequency (rope) and
mean time between collisions with neutral atom (r). The approximate formula for

plasma oscillation is:
(ope z27tx9 ”e (8.1)

and 1: is:

_ 1
Kng

 

2'

(8.2)

where K is the collision rate constant. For argon gas, K is approximately 10'13

m3/s [13], and n9 can be derived using equation 7.1. The calculated value for n,,

is 4.83x1022 m‘3. Thus, 1 is 2x10‘1° s and rope is 4.4x1o11 s". This proves that the

third plasma criterion also fulﬁlled.

8.2 Recommendations

This study created a miniature microwave plasma source. Future work on

the development of microstripline plasma sources should focus on an improved

92

design to minimize power loss due to radiation leakage or characteristic
impedance mismatch. Also, reducing the overall size of the coupling structure is
of the interest.

Another study of interest would be using this miniature plasma source
design for small scale surface treatments or other applications. The microstripline

technology has the potential for being scaled to produce plasmas on a chip.

93

APPENDICES

94

Appendix A

Color Pictures of the Miniature Microstripline Plasma
Source

Images In this Thesis are presented in color.

 

Figure A.1 Argon discharge inside 1 mm i.d. quartz tube generated using
microstripline structure #1.

  

Figure A.2 Argon disharge inside 1 mm i.d. quartz tube generated using
microstripline structure #2.

95

    

Q

a.
Figure A.3 Argon discharge inside a branching 2 mm i.d. quartz tube.

 

Figure A.5 Atmospheric pressure argon discharge showing five filament-like
discharges.

96

Appendix B

QBasic Program for the Optical Emission Spectroscopy

'.L

'|Author: Jayakumaran Sivagnaname; Date: July 1998

'|Monochromator Spec: 2400 lines/mm

'|grating: offset=43x2 Angstrom (updated:08/10/2002)

'|Mcpherson Monochromator must be scanned with increasing wavelength ONL
'|Re-written by Jefrri Narendra; July 2002

'|Modiﬁed by Stanley Zuo and Kadek Hemawan: August 2002

Ill- —— <——— II.-

 

'$INCLUDE: 'c:\gpib—dos\qbasic\qbdecl.bas‘

DECLARE SUB ReportError (fd%, errmsg$)

DECLARE SUB F ILEWRT (prev, pico%, cyc%, i%, RSTALN#, resol#, tottim%,
sec%, TEMP$, BUFF$, count%)

DECLARE SUB RESTART ()

CONST black = 0
CONST blue = 1
CONST green = 2
CONST cyan = 3
CONST red = 4

CONST magenta = 5
CONST brown = 6
CONST white = 7
CONST grey = 8
CONST lightblue = 9
CONST lightgreen = 10
CONST Iightcyan = 11
CONST lightred = 12
CONST lightmagenta = 13
CONST yellow = 14
CONST brightwh'rte = 15

COMMON resol#, cyc%, count%, pico%, i%, RSTALN#, ENDLNl, RENDLNl,
speedl, tottim%, sec%, BUFF$, TEMP$, prev

st1$ = "waveln=["

st2$ = "value=["

EN$ = 00]"

path$ = "C:\QB45\Data"

97

DO WHILE conﬁrm$ <> "y" AND conﬁrm$ <> "Y"
CLS
SCREEN O
LOCATE 1, 3
PRINT "Enter a file name [mmddTrialNumber]: ";
INPUT ﬁlenm$
PRINT "Is the ﬁlename correctIy/n]";
INPUT conﬁrrn$
LOOP

'------ Initialize the device
CALL IBDEV(0, 14, O, T103, 1, O, pico%)
IF (pico% < 0) THEN

CALL ReportError(pico%, "Could not open picoAmpmeter.")
END IF

 

'--- Clear the picoampmeter and set it to default --—
'CALL lBWRT(pico%, "DCL")
'lF (IBSTA% AND EERR) THEN
'CALL ReportError(pico%, "Can't clear the picoAmpmeter")
'END IF

CLS 'Clear the screen

OPEN path$ + "\W' + ﬁlenm$ + ".m" FOR OUTPUT AS #1'store wavelength

value
PRINT #1 , st1$

OPEN path$ + "\D" + ﬁlenm$ + ".m" FOR OUTPUT AS #2'store current value

PRINT #2, st2$
LOCATE 2, 3

PRINT "Values of wavelength stored in ﬁle "; path$ + "\W' + ﬁlenm$ + ".m";

LOCATE 3, 3

PRINT "Values of current stored in file "; path$ + "\D" + filenm$ + ".m";

' Declare temporary variables and constants
BUFF$ = SPACE$(20)

TEMP$ = SPACE$(20)

cycle% = 2

count% = 1

prev = 1E-11

 

 

'---—-- Taking input parameters—mm-
COLOR green, black

98

LOCATE 4, 3

PRINT "Program used for the spectrometer with 2400 lines/mm grating"
COLOR white, black

LOCATE 5, 3

PRINT "Enter the initial scan wavelength [A]";

INPUT STALN!

RSTALN! = 2 * STALN!

RSTALN# = RSTALN!

COLOR yellow, blue

LOCATE 7, 3

PRINT "Set the counter to"; STALN! + (86 I 2)
COLOR white, black

LOCATE 9, 3

PRINT "Enter the ﬁnal scan wavelength [A]";
INPUT ENDLNI

RENDLN! = 2 * ENDLNI

LOCATE 10, 3

PRINT "End point as observed from the counter [A]"; ENDLNI + (86 I 2);
LOCATE 11, 3

PRINT "Enter the speed scanning drive [Almin]";

INPUT speed!

speed! = speed! * 2 'Scan speed is only half of the reading of at spectro meter

'IF speed! <= 0 THEN
'speed! = 100
'LOCATE 11, 3
'PRINT "Default speed (100) is used. Continue?";
'lNPUT ans$

'IF ans$ = "Y" THEN
'END IF
'END IF

LOCATE 13, 3

resol# = speed! I (cycle% * 60)

PRINT 'Waming: The minimum number for resolution : "; resol#; " [Angstrom]"
LOCATE 15, 3

PRINT "Enter a resolution multiplication of above (in integer) ";

INPUT multiple! 'The reason of above is to make sure we a precised round
up (see sec%=sec#)

multiple% = multiple!

resol# = resol# * multiple%

99

 

IF resol# = 0 THEN
resol# = speed! I (cycle% * 60)
END IF

COLOR white, red
LOCATE 16, 3
PRINT "Actual resolution you used is: "; resol#; " [Angstrom]"

sect!t = resol# * (cycle% * 60) I speed!
sec% = secff

 

 

' Accuracy check of old code, NO need any more
'IF (sec% - secilf) > .000001 THEN

'COLOR white, red

'LOCATE 16, 3

'PRINT "Error in calculation is more likely to occur”;
'END IF

 

COLOR white, black

LOCATE 17, 3

PRINT "Data acquisition interval [seconds]"; sec%
TEMP! = ENDLNI - STALN!

IF TEMP! < 0 THEN
LOCATE 19, 3
PRINT "Please scan the spectrometer with increasing value of wavelength"
CALL RESTART
ELSE
numofsamples# = (RENDLN! - RSTALN!) l resol#
numofsamples% = numofsamples#
LOCATE 19, 3
PRINT "No. of samples will be: "; numofsamples%

tottim! = numofsamplesff I cycle%

tottim% = tottim!

LOCATE 20, 3

PRINT "Total time to be taken [in seconds]: "; tottim%

endtim# = tottim! I secs!
endtim% = endtim#

LOCATE 22, 3

COLOR white, red
PRINT "Set Scan drive scanning switch to H";

100

LOCATE 23, 3
COLOR white, red
PRINT "Please check the PicoAmpMeter is at RMT mode";

LOCATE 24, 3

PRINT "Start the Program and the Scan drive simultaneously";
COLOR white, black

LOCATE 25, 3

PRINT "Hit any key to start";

' Set GPIB bus on continuous talk ------
CALL lBWRT(pico%, "TOX")

 

' Set pico% to RMT mode

CALL lBWRT(pico%, "REN")

IF (IBSTA% AND EERR) THEN
CALL ReportError(pico%, "Can't set picoAmpmeter to the remote mode")

END IF

 

 

 

' Set pico$ to AUTO range -----
CALL lBWRT(pico%, "TOX")
CALL lBWRT(pico%, "ROX")
IF (IBSTA% AND EERR) THEN
CALL ReportError(pico%, "You may have to manually set to AUTO range")
END IF

WHILE INKEY$ = ""
WEND

COLOR green, black
i% = 1

CLS

LOCATE 1, 1

PRINT "Program reads data from picoammeter in "; sec% l cycle%; "- second
interval";

LOCATE 2, 1
PRINT "No. of samples to be taken"; numofsamples%;

LOCATE 3, 1
PRINT "Total time will be: "; tottim%; "seconds";

101

LOCATE 5, 1
PRINT 'Wavelength[A] Current[amps] Sample No. Cycle/Sec. Time
remaininglsecl"

TIMER ON
ON TIMER(sec%) GOSUB disp
start! = TIMER

DO
LOOP WHILE (i% - 1) * sec% < tottim% 'keep timer on if remaining time is
greater than 0

ﬁnish! = TIMER
TIMER OFF

PRINT " "

PRINT "Total execution time = "; ﬁnish! - start!; "Seconds"
PRINT #1, EN$

PRINT #2, EN$

' Store data to ﬁles
OPEN path$ + "\X" + ﬁlenm$ + " .m" FOR OUTPUT AS #3'store matlab EXE ﬁle

PRINT #3, "clear all; cIc"

PRINT #3, 'W" + ﬁlenm$

PRINT #3, "D" + ﬁlenm$

PRINT #3, "plot(waveln,abs(value),'g');pause(3);sm5;xlabel(Wavelength

A');ylabel('Current amps');"

PRINT #3, "title('Emission Spectrum');grid;"

PRINT "Execute "; path$ + "\X" + ﬁlenm$ + ".m"; " in matlab to view plot"
CLOSE

 

 

CALL RESTART 'Finish or restart the program
END

 

A sub program based on the timer ----—

disp:

FOR cyc%= 1 TO cycle%

CALL FlLEWRT(prev pico%, cyc%, i%, RSTALN#, resol#, tottim%, sec%,
TEMP$, BUFF$, count%)

count% = count% + 1

NEXT cyc%

i% = i% + 1

RETURN

END IF 'Following the last else statement

102

END Whole program ends

SUB FILEWRT (prev, pico%, cyc%, i%, RSTALN#, resol#, tottim%, sec%,
TEMP$, BUFF$, count%)

Trigger pico% for reading ---—--
CALL lBWRT(pico%, "GET")

 

 

 

' Read the picoAmeter
CALL lBRD(pico%, BUFF$)
'IF (IBSTA% AND EERR) THEN

'CALL ReportError(pico%, "Could not read picoAmpmeter setting")
'END IF

'To enforce read function, don‘t use error checking function to
'avoid read failure

' Store the value last read in TEMP
TEMP$ = MID$(BUFF$, 5, 20)
y = VAL(RTRIM$(TEMP$))

 

 

IF (y > .00001) THEN
y = prev
END IF

‘——--—-—- Calculate and display parameters onto screen ----—-
prev = y

RSTALN# = RSTALN# + resol#

RSTALN! = RSTALN#

WRITE #1, RSTALN!
WRITE #2, -1 * y
LOCATE 7, 1
PRINT RSTALN!, y, count%, cyc%, tottim% - (sec% * i%)
END SUB
SUB ReportError (fd%, errmsg$) STATIC
PRINT "Error =", IBERR%; errmsg$
IF (fd% <> -1) THEN
PRINT ("Cleanup: taking board off-line")

CALL I BONL(fd%, 0)
END IF

103

STOP 'Abort program
END SUB
SUB RESTART

 

Place the Device Ofﬂine -----—
CALL IBONL(pico%, 0)

 

Instruct the User Terminating the Program -—-—--
PRINT " "

COLOR white, red

PRINT "Switch off the Spectrometer dn've"

COLOR white, black

PRINT "Press any key to restart or end the program";

WHILE INKEY$ = ""

HTONE = 2000: LTONE = 550: DELAY = 500
FOR count = HTONE TO LTONE STEP -10
SOUND count, DELAY I count

NEXT count

HTONE = 780: RANGE = 650

FOR count = RANGE TO -RANGE STEP -4
SOUND HTONE - ABS(count), .3

count = count - 2 l RANGE

NEXT count

WEND

END SUB

104

Appendix C

QBasic Program for the Double Langmuir Probe

'.L

'| Double Langmuir Probe l-V curve measurement I
'| Programed by Meng-hua Tsai, customized by Mark Perrin 9I97 |
'| Modiﬁed by Stanley Zuo 02/02 |
0+ .1.

 

'$INCLUDE: 'c:\gpib-dos\qbasic\qbdecl.bas'
DECLARE SUB ReportError (fd%, errmsg$) ' Error subroutine
' Bring the Power suppply/ PicoAmp meter on-Iine

CALL IBDEV(0, 1, 0, T1s, 1, 0, dm1%)
IF (dm1% < 0) THEN

CALL ReportError(dmm%, "Could not open Ampmeter.")
END IF

CALL IBDEV(0, 2, 0, T1s, 1, 0, dmm%)
IF (dmm% < 0) THEN

CALL ReportError(dmm%, "Could not open Power Supply")
END IF

CLS

PRINT " Double Langmuir probe l-V curve Measurement"
PRINT ""

INPUT "Input ﬁlename for storing data 2"; name$

name$ = "c:\zuo\dlp\" + name$

PRINT "Data stored in ﬁle z"; name$

OPEN name$ FOR OUTPUT AS #2

INPUT "Input voltage increment (volt) = "; dv!
totl% = 100Idv! + 1

PRINT #2, totl%

ini! = 0

num% = 0

DO WHILE ini! < 100

num% = num% + 1
ini! = (num% - 1) * dv!

105

Vi$ = STR$(ini!)

LOCATE 8, 1
PRINT "vi="; VI$

'Set voltage to volmeter

devbuf$ = "VSET " + Vi$
CALL IBWRT(dmm%, devbuf$)
' CALL IBWRT(dmm%, "VOUT?")

'Request data readings from device

LOCATE 20, 1
INPUT "Ready to take data (yln)?", idx$
IF idx$ = "n" THEN
CALL IBONL(dmm%, 0)
CALL lBONL(dm1%, 0)
END
ELSE

' ctime$ = TIME$

' TIME$ = "00:00:00"

' WHILE TIME$ < "00:00:03"
' LOCATE 21, 1

' PRINT TIME$

' WEND

'Take the average of 20 readings for each vol/cur point
Vol = 0
lo! = 0
Reading$ = SPACE$(20)

FOR i% = 1 TO 20

CALL IBWRT(dmm%, "VOUT?")

' IF (IBSTA% AND EERR) THEN

' CALL ReportError(dmm%, "Could not trigger multimeter")
' END IF

' Read data from dmm
CALL IBRD(dmm%, Reading$)
IF (IBSTA% AND EERR) THEN

CALL ReportError(dmm%, "Could not read data from power supply")
END IF

106

'Remove blank spaces in READING$ and store the result in R03.
R03 = LEFT$(Reading$. IBCNT%)
'Request current reading from dm1

'CALL lBWRT(dm1%, "Amp; Auto")

‘IF (IBSTA% AND EERR) THEN

' CALL ReportError(dm1%, "Can't trigger Ampmeter")
‘END IF

CALL IBRD(dm1°/o, Reading$)
IF (IBSTA% AND EERR) THEN

CALL ReportError(dm1%, "Can't read data from Amp meter")
END IF

' rd1$ = LEFT$(Reading$, IBCNT%)
rd1$ = Reading$

' LOCATE 9. 1
' PRINT LEN(RD$); LEN(rd1$)
' PRINT "Voltage/Current read: "; RD$; rd1$

vol! = VAL(RD$) - 50
cur! = VAL(rd1$)

cur! = cur! * 1000

LOCATE 12, 1
PRINT "Voltage(V)/current(mA) : "
LOCATE 12, 1
PRINT "VoItage(\I)Icurrent(mA) 2"; vol!; cur!
lo! = lo! + cur!

NEXT i%

' END IF

lo! = lo! I20

PRINT "Average currenr = "

LOCATE 13, 1

PRINT "Average current ="; Io!
PRINT #2, vol!; Io!
LOOP

‘Take dmm off-line

107

CLOSE #2

CALL IBONL(dmm%, 0)

CALL IBONL(dm1%, 0)

END

SUB ReportError (fd%, errmsg$) STATIC

PRINT "Error = ", IBERR%; errmsg$

IF (fd% <> -1) THEN
PRINT ("Cleanup: taking board off-line")
CALL IBONL(fd%, 0)

END IF

STOP 'Abort program

END SUB

108

Appendix D

Discharge Volume and Power Density Measurements
Results

D.1 Argon Discharges

D.1.1. Microstripline Structure #1

0.1.1.1. 1 mm i.d. discharge tube
0.1.1.1.1. Flow rate: 2 sccm

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure: 0.08 Torr
AbsorbedQN) Left Right Length (cm) Vol(cm3) Density(Wcm‘3)
0.7 8.7 8.1 1.4 1.10502 61.8
1.2 8.4 8.1 1.7 1.34502 91.8
4.0 5.9 8.9 3.0 2.38502 170.9
8.8 5.7 9.0 3.3 2.59502 255.8
9.7 5.4 9.2 3.8 2.98E-02 324.8
13.1 5.3 9.3 4.0 3.14502 417.4
18.5 5.7 9.0 3.3 2.59502 837.8
20.5 4.9 9.8 4.7 3.69E-02 555.7
Pressure: 5.0 Torr
Absorbed(W) Left Right Lemth (cm) Vol(cm°) Density(Wcm°)
1.5 8.2 8.5 2.3 1.81E-02 80.3
4.0 5.8 8.9 3.1 2.43502 185.4
6.9 5.5 9.1 3.8 2.83502 242.3
9.9 5.1 9.5 4.4 3.46E-02 288.9
13.3 5.0 9.6 4.8 3.61E-02 389.2
18.8 5.1 9.4 4.3 3.38502 498.1
20.7 4.8 9.8 5.0 3.93502 528.1
Pressure: 10 Torr
Absorbed(W) Left Right Length (cm) Vol(cm3) Density(Wcm‘3)
1.4 8.2 8.2 2.0 1.57502 88.8
4.0 5.8 8.9 3.1 2.43502 185.4
7.0 5.3 9.3 4.0 3.14502 221.7
10.0 5.0 9.6 4.8 3.81502 277.5
13.5 5.0 9.6 4.8 3.81502 372.3
18.9 5.0 9.6 4.6 3.61E—02 488.4
20.8 4.8 9.9 5.1 4.01502 519.1

 

 

 

 

 

 

109

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure: 25 Torr
AbsorbedM) Left Right lﬂgth (cm) Vol(cm3) Density(Wcm4)
1.5 8.2 8.1 1.9 1.49502 97.2
4.2 5.8 8.9 3.1 2.43502 172.4
7.1 5.4 9.2 3.8 2.98502 237.1
10.1 5.1 9.4 4.3 3.38502 300.2
13.8 5.0 9.6 4.6 3.61E-02 375.5
17.0 5.2 9.5 4.3 3.38E-02 502.8
20.9 4.9 9.7 4.8 3.77502 554.8
Pressure: 50 Torr
Absorbed(W) Left Rim Lengtmcm) Vol(cm3) Density(wcm“)
4.3 5.7 8.1 2.4 1.88502 225.8
7.3 5.5 9.1 3.6 2.83502 258.2
10.3 5.3 9.3 4.0 3.14502 328.1
13.8 5.2 9.4 4.2 3.30502 418.0
17.2 5.2 9.4 4.2 3.30502 521.8
21.1 5.0 9.7 4.7 3.89502 571.0
D.1.1.1.2. Flow rate: 10 sccm
Pressure: 0.08 Torr
Absorbed(W) Left Right lingth (cm) Vol(cm3) Density(Wcm")
0.8 8.1 8.8 2.5 2.0502 29.8
1.9 5.5 9.3 3.8 3.0502 83.7
4.8 4.7 10.1 5.4 4.2502 113.5
7.8 4.2 10.8 8.4 5.0502 152.0
10.8 4.0 10.8 8.8 5.3502 199.3
14.1 4.0 10.8 8.8 5.3502 283.5
17.5 3.6 11.2 7.6 8.0502 293.9
21.4 3.5 11.2 7.7 6.0E-02 353.2
Pressure: 5.0 Torr
Absorbed(W) Left Right Length an) Vol(cm3) Density(Wcm’3)
0.7 5.9 8.8 2.9 2.28502 30.4
2.0 5.2 9.6 4.4 3.48502 58.3
5.0 4.4 10.4 8.0 4.71502 105.8
7.8 3.8 10.9 7.1 5.58502 1400
10.8 3.5 11.3 7.8 8.13502 178.5
14.2 3.4 11.4 8.0 8.28502 225.7
17.6 3.4 11.4 8.0 8.28502 280.1
21.5 3.2 11.8 8.4 8.80502 325.4

 

 

 

 

 

 

 

110

 

 

 

Pressure: 10 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbed(W) Left Right Length (cm) VolQm’) Density(Wcm’3)

0.7 5.9 8.8 2.9 2.28502 30.4

2.0 5.2 9.6 4.4 3.46E-02 58.3

4.9 4.3 10.4 8.1 4.79502 102.9

7.8 3.8 10.9 7.1 5.58E-02 139.0

10.8 3.5 11.3 7.8 8.13502 176.5

14.2 3.4 11.4 8.0 6.28E-02 225.7

17.7 3.5 11.3 7.8 8.13502 288.2

21.5 3.2 11.6 8.4 8.80502 325.4
Pressure: 25 Torr

Absorbed(W) Left Right Length (cm) Vol(cm3) DensityMcm")

0.7 5.9 8.8 2.9 2.28E-02 30.4

2.0 5.1 9.6 4.5 3.53502 57.0

4.9 4.3 10.4 8.1 4.79502 102.9

7.9 3.8 11.0 7.2 5.85502 139.1

10.9 3.5 11.3 7.8 8.13502 177.4

14.2 3.4 11.3 7.9 8.20502 229.5

17.7 3.4 11.3 7.9 8.20502 284.8

21.5 3.3 11.5 8.2 8.44502 334.2
Pressure:50Torr

Absorbed(W) Left Rigm igngth (cm) Vol(cm3) Density(Wcm‘3)

0.7 5.8 8.1 2.3 1.81502 38.4

2.2 5.3 9.5 4.2 3.30502 88.2

5.1 4.8 10.3 5.7 4.48502 113.9

7.9 4.1 10.7 8.8 5.18502 152.8

10.9 3.7 11.0 7.3 5.73502 190.6

14.3 3.8 11.2 7.8 5.97502 239.5

17.8 3.7 11.1 7.4 5.81502 305.7

21.8 3.3 11.5 8.2 8.44502 335.1
Pressure: 100 Torr

Absorbed(W) Left Right Lngth (cm) Vol(cm3) Density(Wcm°)

3.8 5.4 9.3 3.9 3.08502 122.9

5.0 5.1 9.8 4.5 3.53502 142.8

7.9 4.7 10.1 5.4 4.24502 185.4

10.9 4.5 10.3 5.8 4.58502 238.8

14.2 4.4 10.5 8.1 4.79502 297.2

17.7 4.4 10.5 8.1 4.79502 388.5

21.5 4.3 10.7 8.4 5.03502 428.3

 

 

 

 

 

 

111

 

 

 

 

 

Pressure: 150 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbed(W) Left RiLht Le_ngth (cm) Vo|(cm3) Density(Wcm'3)

3.5 5.8 8.9 3.3 2.59502 134.4

4.8 5.4 9.1 3.7 2.91502 185.7

7.8 5.0 9.6 4.8 3.81502 214.8

10.8 4.8 9.9 5.1 4.01502 288.8

14.1 4.7 10.0 5.3 4.18502 339.4

17.5 4.8 10.0 5.2 4.08502 429.5

21.3 4.5 10.3 5.8 4.58502 487.8
Pressure: 200Ton

Absorbed(W) Left Right Length (cm) Vochm’) DensiMWcm")

4.5 5.7 8.8 3.1 2.43502 183.9

7.5 5.3 9.3 4.0 3.14502 239.8

10.8 5.0 9.6 4.6 3.61E—02 294.6

14.0 5.0 9.7 4.7 3.89502 379.7

17.4 5.1 9.5 4.4 3.46E—02 504.4

21.2 4.8 9.9 5.1 4.01502 530.4
Pressure: 300Torr

Absorbed(W) Left Right Length (cm) Vol(cm3) Density(Wcm’3)

4.1 5.8 8.8 2.8 2.20502 188.3

7.0 5.8 8.8 3.0 2.38502 295.5

10.1 5.6 8.9 3.3 2.59502 389.0

13.5 5.5 9.0 3.5 2.75502 491.4

18.8 5.6 8.8 3.2 2.51502 888.8

21.0 5.1 9.9 4.8 3.77502 558.1
Pressurez400Torr

Absorbed(W) Left Ri ht Length (cm) Vol(cm3) Densityorvcmi

9.8 5.5 9.0 3.5 2.75502 358.5

13.2 5.4 9.0 3.8 2.83502 485.8

18.5 5.5 8.9 3.4 2.87502 819.0

20.5 5.4 9.0 3.6 2.83502 725.5
Pressure: 500Torr

Absorbedom Left Right Length (cm) Vol(cm3) Density(Wcm‘3)

12.7 5.6 8.8 3.2 2.51502 503.9

 

 

 

 

 

 

112

 

 

 

 

 

0.1.1.1.3. Flow rate: 20 sccm

 

Pressure: 0.15 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbed(W) Left Right Length (cm) Vol(cm3) Density(Wcm"’)
0.6 5.9 8.9 3.0 2.36E-02 27.0
2.0 5.2 9.7 4.5 3.53E-02 57.0
4.9 4.4 10.5 6.1 4.79E-02 102.9
7.8 4.0 10.9 6.9 5.42E—02 143.0
10.8 3.7 11.3 7.6 5.97E-02 180.2
14.1 3.6 11.3 7.7 6.05E-02 233.6
17.5 3.3 11.7 8.4 6.60E-02 265.9
21.4 3.2 11.7 8.5 6685-02 320.8
Pressure: 5.0 Torr
Absorbed(W) Left Right Length (cm) Vol(cm3) Density(Wcm“’)
0.8 5.6 9.2 3.6 2.83E—02 28.5
2.1 5.0 9.9 4.9 3.85E—02 55.3
5.1 4.2 10.7 6.5 5.11E-02 99.8
7.9 3.7 11.2 7.5 5.89E-02 134.5
10.9 3.4 11.5 8.1 6.36E—02 170.9
14.3 3.2 11.6 8.4 6.60E-02 216.7
17.7 3.4 11.5 8.1 6365-02 278.4
21.6 3.0 11.9 8.9 6.99E-02 308.8
Pressure: 10 Torr
Absorbed(W) Left Light Leggth (cm) Vol(cm3) DensityONcm")
0.8 5.7 9.1 3.4 2.67E-02 30.2
2.1 5.0 9.9 4.9 3.85E-02 55.3
5.0 4.1 10.8 6.7 5.26E-02 95.8
7.9 3.6 11.3 7.7 6.05E-02 130.0
10.9 3.3 11.6 8.3 6.52E-02 166.7
14.2 3.2 11.7 8.5 6.68E-02 213.3
17.7 3.2 1 1.7 8.5 6.68E-02 265.3
21.6 3.0 12.0 9.0 7.07E-02 305.3
Pressure: 25 Torr
Absorbed(W) Left Right Length (cm) Vol(cm3) Density(Wcm‘3)
0.9 5.7 9.2 3.5 2.75E-02 31.4
2.2 5.0 9.9 4.9 3.85E-02 56.7
5.1 4.1 10.7 6.6 5.18E—02 98.3
7.9 3.6 11.3 7.7 6.05E—02 131.0
10.9 3.3 11.5 8.2 6.44E-02 169.7
14.3 3.2 11.7 8.5 6.68E—02 214.1
17.7 3.2 11.7 8.5 6.68E-02 265.3
21.6 3.0 11.9 8.9 6.99E-02 308.8

 

 

 

 

 

 

113

 

 

 

 

 

Pressure: 50 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbedm Left Right Length gm) Vol(cm3) Densitywvcm“)

0.9 5.8 8.9 3.1 2.43502 37.7

2.2 5.1 9.8 4.7 3.69E-02 80.7

5.2 4.3 10.6 8.3 4.95502 104.2

8.0 3.9 11.0 7.1 5.58502 143.1

11.0 3.5 11.4 7.9 6.20E-02 177.0

14.4 3.4 11.5 8.1 8.38502 225.8

17.8 3.4 11.5 8.1 8.38502 279.3

21.6 3.2 11.8 8.8 8.75502 320.4
Pressure: 100 Torr

Absorbed(W) Left Right Leggth (cm) Vol(cm3) Density(Wcm°)

1.1 5.7 9.0 3.3 2.59502 44.1

2.5 5.4 9.3 3.9 3.06E-02 80.4

5.4 4.7 10.1 5.4 4.24502 128.8

8.2 4.3 10.6 8.3 4.95502 185.8

11.2 4.0 10.9 6.9 5.42502 205.8

14.5 4.0 11.0 7.0 5.50502 283.1

18.0 4.2 10.8 6.6 5.18502 347.1

21.8 3.7 11.3 7.6 5.97502 384.4
Pressure: 150 Torr

Absorbed(W) Left Right Legqth (cm) Vol(cm°) Density(Wcm°)

2.1 5.8 8.8 3.0 2.36E-02 90.2

5.3 5.0 9.7 4.7 3.89502 142.7

8.0 4.7 10.1 5.4 4.24502 189.4

11.0 4.4 10.4 8.0 4.71502 234.3

14.4 4.4 10.5 6.1 4.79502 299.8

17.9 4.5 10.4 5.9 4.83502 385.9

21.6 4.1 10.8 8.7 5.28502 411.2
Pressure: 200 Torr

Absorbed(W) Left light Leggth (cm) Vol(cm3) Densincm")

3.7 5.7 8.9 3.2 2.51502 145.4

5.0 5.4 9.2 3.8 2.98502 188.9

8.0 4.9 9.7 4.8 3.77502 211.8

11.0 4.7 10.0 5.3 4.18502 283.8

14.4 4.6 10.1 5.5 4.32502 332.3

17.8 4.7 10.1 5.4 4.24502 418.9

21.6 4.4 10.4 6.0 4.71502 459.2

 

 

 

 

 

 

114

 

 

 

 

 

 

 

Pressure: 300 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbem Left Right Lenggt (cm) Vol(cm3) Density(Wcm‘3)
4.4 5.9 8.8 2.9 2.28502 191.7
7.5 5.4 9.2 3.8 2.98E-02 250.3
10.6 5.2 9.5 4.3 3.38E—02 313.5
14.0 5.0 9.6 4.8 3.81502 387.9
17.4 5.1 9.5 4.4 3.46E—02 504.4
21.3 4.9 9.8 4.9 3.85502 553.5
Pressure: 400 Torr
Absorbed(W) Left Right Length (cm) Vol(cm3) Density(Wcm'3)
7.0 5.9 8.9 3.0 2.36E-02 295.5
10.2 5.8 9.1 3.5 2.75502 370.9
13.7 5.5 9.2 3.7 2.91502 470.7
17.0 5.5 9.1 3.6 2.83502 802.5
21.1 5.2 9.4 4.2 3.30502 838.9
Pressure:500Torr
Absorbed(W) Left Right Lengmrcm) Vol(cm3) Density(Wcm")
9.6 8.0 8.8 2.8 2.20502 438.0
13.1 5.9 8.8 2.9 2.28502 573.3
18.4 6.0 8.8 2.8 2.20502 748.5
20.6 5.6 9.0 3.4 2.67E-02 770.3
Pressure: 600 Torr
Absorbed(W) Left Right Leggth 1cm) Vol(cm3) Density(Wcm'°)
12.7 5.8 8.8 3.0 2.38502 539.8
Pressure: 700 Torr
Absorbed(W) Left Right Lengg (cm) Vol(cm3) DensityoNcm“)
12.2 6.0 8.7 2.7 2.12502 575.9
0.1.1.1.4. Flow rate: 40 sccm
Pressure: .018 Torr
Absorbed(W) Left Right Leggth (cm) Vol(cm3) DensityMcm")
0.7 5.7 9.2 3.5 2.75502 27.3
2.1 5.1 9.9 4.8 3.77502 58.4
4.9 4.4 10.7 6.3 4.95502 99.8
7.8 4.0 11.3 7.3 5.73502 135.2
10.8 3.7 11.4 7.7 6.05E—02 177.9
14.1 3.8 11.6 8.0 8.28502 224.8
17.5 3.7 11.5 7.8 8.13502 288.4
21.5 3.3 11.8 8.5 8.88502 321.8

 

 

 

 

 

 

 

115

 

 

 

 

 

Pressure: 5.0 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbed(W) Left Right Lenﬁh (cm) Vol(cm3) Density(Wcm‘3)
0.9 5.5 9.9 4.4 3.46E-02 28.8
2.2 5.0 10.0 5.0 3.93502 57.0
5.2 4.2 10.9 8.7 5.28502 97.9
8.0 3.7 11.9 8.2 8.44502 123.9
11.0 3.4 11.7 8.3 8.52502 188.5
14.4 3.3 11.8 8.5 6.68E—02 215.0
17.8 3.3 11.8 8.5 8.88502 266.2
21.6 3.1 12.0 8.9 8.99502 309.8
Pressure: 10 Torr
Absorbed(W) Left Rght Length (cm) Vol(cm3) Density(Wcm")
0.9 5.4 9.4 4.0 3.14502 29.2
2.2 4.9 10.0 5.1 4.01502 55.9
5.2 4.1 10.9 6.8 5.34502 98.5
8.0 3.7 11.8 8.1 6.36E-02 125.4
11.0 3.4 11.7 8.3 8.52502 188.5
14.4 3.2 11.8 8.8 8.75502 212.5
17.8 3.3 11.8 8.5 8.88502 266.2
21.8 3.1 11.9 8.8 8.91502 313.1
Pressure: 25 Torr
Absorbed(W) Left Right Lenggi (cm) Vochma) Density(Wcm")
0.9 5.8 9.3 3.7 2.91502 31.8
2.2 4.9 10.0 5.1 4.01502 55.9
5.2 4.2 10.9 8.7 5.28502 97.9
8.0 3.7 11.4 7.7 8.05502 131.9
11.0 3.4 11.7 8.3 8.52502 188.5
14.4 3.3 11.8 8.5 6.68E-02 215.0
17.8 3.3 11.8 8.5 6.68E-02 266.2
21.6 3.1 11.9 8.8 6.91E-02 313.1
Pressure:50Torr
Absorbed(W) Left Ri ht Length (cm) Vol(cm3) Density(Wcm")
1.0 5.7 9.2 3.5 2.75502 35.5
2.4 5.0 9.9 4.9 3.85502 81.1
5.2 4.3 10.7 6.4 5.03502 103.8
8.0 3.9 11.1 7.2 5.85502 142.1
11.0 3.6 11.5 7.9 6.20E-02 177.9
14.4 3.5 11.6 8.1 8.38502 228.5
17.8 3.5 11.6 8.1 8.38502 280.2
21.6 3.3 11.7 8.4 6.60E-02 328.0

 

 

 

 

 

 

116

 

 

 

 

 

Pressure: 100 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbed(W) Left R‘ ht Leggm (cmL Vochm’) Density(Wcm°)
2.1 5.8 9.2 3.6 2.83E-02 73.8
2.7 5.3 9.4 4.1 3.22502 83.5
5.6 4.6 10.3 5.7 4.48502 125.2
8.4 4.2 10.8 6.6 5.18502 181.5
11.4 4.0 11.0 7.0 5.50502 208.9
14.7 3.9 11.2 7.3 5.73502 257.2
18.2 4.0 11.1 7.1 5.58E-02 325.7
22.0 3.7 11.4 7.7 6.05E—02 384.3
Pressure: 150 Torr
Absorbed(W) Left Right Length (cm) Vol(cm’) Density(Wcm4)
2.5 5.8 9.0 3.2 2.51502 98.0
5.5 5.0 9.8 4.8 3.77502 145.7
8.3 4.6 10.2 5.8 4.40502 189.0
11.3 4.4 10.8 6.2 4.87502 231.3
14.7 4.3 10.7 6.4 5.03502 292.3
18.1 4.4 10.8 6.2 4.87E-02 371.8
21.9 4.1 11.0 6.9 5.42502 403.5
Pressure:200Torr
Absorbed(W) Left Right Leggth (cm) Vol(cm3) Density(Wcm"’)
4.1 5.6 9.2 3.6 2.83502 145.1
5.4 5.3 9.5 4.2 3.30502 183.1
8.2 4.9 9.9 5.0 3.93502 208.9
11.2 4.6 10.2 5.6 4.40502 254.8
14.8 4.5 10.3 5.8 4.56E—02 321.3
18.1 4.6 10.3 5.7 4.48502 404.4
21.9 4.3 10.5 6.2 4.87E-02 449.0
Pressure: 300Torr
Absorbed(W) Left Right Length (cm) Vol(cm3) Density(Wcm")
4.7 5.9 9.0 3.1 2.43502 193.2
7.9 5.5 9.4 3.9 3.08502 258.8
11.0 5.1 9.6 4.5 3.53502 310.7
14.4 5.0 9.7 4.7 3.89502 390.3
17.8 5.1 9.6 4.5 3.53502 504.3
21.6 4.8 9.9 5.1 4.01502 540.2
Pressure:400Torr
Absorbed(W) Left Right Length (cm) Vof(cm§) Density(Wcm’3)
7.2 6.0 9.0 3.0 2.36E-02 307.5
10.5 5.7 9.2 3.5 2.75502 383.1
14.0 5.5 9.3 3.8 2.98E-02 489.8
17.4 5.6 9.2 3.8 2.83E-02 818.5
21.4 5.3 9.5 4.2 3.30502 849.2

 

 

 

 

 

 

117

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure:500Torr
Absorbed(W) Left Right Lengtp (cm) Vol(cm3) Density(Wcm")
9.9 6.1 8.8 2.7 2.12502 487.5
13.3 6.0 8.9 2.9 2.28502 585.7
18.8 8.1 8.8 2.7 2.12502 790.1
20.9 5.6 9.2 3.8 2.83E-02 737.4
Pressure:000Torr
Absorbed(W) Left Right Le_ngth (cm) Vol(cm3) Densityrvvcm‘)
13.1 5.9 9.0 3.1 2.43502 538.8
Pressure: 700 Torr
Absorbed(W) Left Right Length (cm) Vol(cm3) Density(Wcm‘°’)
13.1 6.1 8.8 2.7 2.12502 818.4

 

 

 

 

 

 

 

D.1.1.2. 2 mm i.d. discharge tube, flow rate: 20 sccm

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure = 0.40 Torr
Absorbed Left Length
(W) (cm) Righucm) (cm) Vol (cm‘3) PNoIMIcm‘3)
1.0 14.1 16.5 2.4 7.54E-02 13.7
2.2 13.1 17.5 4.4 1.38E-01 16.2
4.8 11.3 19.4 8.1 2.54E-01 18.7
7.0 10.3 20.3 10.0 3.14E-01 22.2
9.4 9.1 21.5 12.4 3.90E—01 24.1
12.5 8.0 22.3 14.3 4.49E-01 27.8
15.6 7.1 22.8 15.7 4.93E-01 31.7
19.0 6.3 22.8 16.5 5.18E-01 36.6
22.1 5.8 23.3 17.5 5.50E-01 40.1
Pressure = 1.0 Torr
Absorbed Left Length
(W) (cm) Righucm) (cm) Vol (cm‘3) PNoKWIcm‘3)
1.0 14.2 16.4 2.2 6.91 E-02 14.9
2.1 13.1 17.5 4.4 1.38E-01 15.4
4.7 11.5 19.4 7.9 2.48E-01 18.9
7.0 10.3 20.3 10.0 3.14E—01 22.2
9.4 9.2 21.3 12.1 3.80E-01 24.7
12.3 8.0 22.3 14.3 4.49E-01 27.4
15.5 7.1 22.7 15.6 4.90E—01 31.7
18.6 6.2 23.1 16.9 5.31 E-01 35.0
21.5 5.6 23.3 17.7 5.56E-01 38.7

 

 

 

 

 

 

118

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure = 2.0 Torr
Absorbed Left Length
(W) ﬁm) nghucm) (my Vol (cm‘3) PNoIMIcm‘3)
1.0 14.2 16.4 2.2 6.91E-02 14.9
2.1 13.1 17.5 4.4 1.38E-01 15.0
4.6 11.3 19.5 8.2 2.58E-01 17.8
6.9 10.2 20.3 10.1 3.17E-01 21.8
9.3 9.1 21.5 12.4 3.90E-01 23.9
12.2 7.9 22.3 14.4 4.52E-01 27.0
15.2 7.0 22.9 15.9 5.00E-01 30.4
18.6 6.3 23.1 16.8 5.28E—01 35.2
21.4 5.5 23.3 17.8 5595-01 38.2
Pressure =3 3.0 Torr
Absorbed Left Length
(W) (cm) nghucm) (cm) Vol (cm‘s) PNoKWIcm‘3)
1.0 14.3 16.1 1.8 5.65E-02 18.2
2.0 13.1 17.5 4.4 1.38E-01 14.6
4.6 11.0 19.5 8.5 2.67E—01 17.2
6.9 10.3 20.3 10.0 3.14E—01 22.0
9.3 9.1 21.5 12.4 3905-01 23.9
12.2 8.0 22.3 14.3 4.49E-01 27.2
15.3 7.0 22.9 15.9 5.00E-01 30.6
18.5 6.2 23.1 16.9 5315-01 34.8
21.5 5.5 23.4 17.9 5.62E-01 38.2
Pressure = 5.0 Torr
Absorbed Left Length
(W) (cm) Righﬂcm) (cm) Vol (cm‘3) PNeIMIcm‘3)
0.9 14.1 16.5 2.4 7.54E-02 12.2
2.1 13.1 17.5 4.4 1.38E-01 15.0
4.6 11.0 19.4 8.4 2.64E-01 17.6
6.9 10.3 20.3 10.0 3.14E-01 21.8
9.3 9.1 21.5 12.4 3.90E-01 23.9
12.2 7.8 22.5 14.7 4.62E-01 26.4
15.3 7.0 22.9 15.9 5.00E-01 30.6
18.4 6.2 23.1 16.9 5.31E-01 34.6
21.4 5.5 23.3 17.8 5.59E-01 38.3
Pressure = 10.0 Torr
Absorbed Left Length
(W) (cm) nght(cm) (cmL Vol (cm‘3) PNoKWIcm‘3)
0.9 14.2 16.3 2.1 6.60E-02 13.9
2.1 13.2 17.5 4.3 1.35E-01 15.7
4.7 11.3 19.3 8.0 2.51E-01 18.7
6.9 10.3 20.2 9.9 3.1 1E-01 22.0
9.3 9.3 21.5 12.2 3.83E-01 24.2
12.3 8.2 22.3 14.1 4.43E-01 27.8
15.4 7.2 22.6 15.4 4.84E-01 31.8
18.5 6.4 23.0 16.6 5.22E-01 35.4

 

 

 

119

 

 

 

_x- "5'
‘3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

21.8 5.8 I 23.2 I 17.4 I 5.47501 1 39.8 I
Pressure =- 20.0 Torr
Absorbed Left Length
(W) (cm) Righucm) (cm) Vol (cm‘3) PNoI(WIcm§)
1.0 14.5 16.1 1.6 5.03E—02 20.5
2.2 13.1 17.3 4.2 1.32E-01 17.0
4.6 11.5 18.7 7.2 2.26E-01 20.3
7.0 10.5 20.0 9.5 2.98E-01 23.3
9.4 9.9 20.5 10.6 3.33E—01 28.2
12.2 8.9 21.5 12.6 3.96E—01 30.9
15.2 8.0 22.3 14.3 4.49E-01 33.8
18.8 7.3 22.5 15.2 4.78E-01 39.3
21.6 6.7 22.9 16.2 5.09E-01 42.5
Pressure = 30.0 Torr
Absorbed Left Length
M (cm) We!) (cm) Vol (cm‘3) PNoI(WIcm*3
1.5 14.5 16.1 1.6 5.03E-02 28.9
4.3 12.6 17.9 5.3 1675-01 25.5
6.6 11.5 18.3 6.8 2145-01 31.0
9.4 10.7 20.0 9.3 2.92E-01 32.2
12.4 10.3 20.5 10.2 3.20E-01 38.8
15.4 9.4 21.3 11.9 3.74E-01 41.2
18.9 8.5 21.6 13.1 4.12E-01 46.0
22.3 8.0 22.0 14.0 4.40E-01 50.7
Pressure 8 50.0 Torr
Absorbed Left Length
(W) (cm) Righqcm) (cm) Vol (cm‘3) PNoI(WIcm*3)
4.6 13.1 17.7 4.6 1.45E-01 32.2
6.9 12.0 18.3 6.3 1.98E-01 34.6
9.2 11.5 18.7 7.2 2.26E-01 40.6
12.1 10.7 19.6 8.9 2.80E-01 43.3
15.6 10.5 20.2 9.7 3.05E-01 51.3
19.3 9.7 21.0 11.3 3.55E-01 54.3
22.6 9.2 21.5 12.3 3.86E-01 58.6
Pressure = 100 Torr
Absorbed Left Length
M (cm) nghucm) (cm) Vol (cm‘3) PNoI(WIcm“3)
5.6 13.4 17.5 4.1 1.29E—01 43.3
7.0 13.0 17.9 4.9 1.54E-01 45.2
9.3 12.3 18.3 6.0 1885-01 49.3
12.0 12.0 18.6 6.6 2.07E—01 57.8
14.7 11.6 18.9 7.3 2.29E-01 64.2
18.3 11.2 19.4 8.2 2.58E-01 70.9
21.9 10.7 20.1 9.4 2.95E—01 74.3
26.2 10.3 20.7 10.4 3.27E-01 80.1

 

 

 

 

 

 

120

 

 

 

 

 

 

 

Pressure = 200 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbed Left Length
(W) (cm) Righqcm) (cm) Vol (cm‘3) PNoI(WIcm‘3)
9.4 13.2 17.8 4.6 1.45E-01 65.1
12.7 12.7 18.1 5.4 1.70E-01 74.6
15.4 12.4 18.3 5.9 1.85E-01 83.1
18.6 12.0 18.6 6.6 2.07E-01 89.7
21.1 11.8 18.7 6.9 2.17E-01 97.4
24.5 11.3 19.0 7.7 2.42E-01 101.2

Pressure = 300 Torr

Absorbed Left Length
(W) (cm) Rilhqcm) (cm) Vol (cm‘3) PNoKWIcm‘3)
11.3 13.5 17.5 4.0 1.26E-01 90.0
15.4 12.9 17.9 5.0 1.57E-01 98.1
18.9 12.7 18.2 5.5 1.73E—01 109.6
22.3 12.6 18.4 5.8 1.82E-01 122.3
25.1 12.0 18.6 6.6 2.07E-01 121.3

Pressure =- 400 Torr

Absorbed Left Length
(W) (cm) ht(cm) (cm) Vol (cm‘3) PNoI(WIcm*3)
11.9 13.5 17.2 3.7 1.16E-01 102.0
15.1 13.1 17.8 4.7 1.48E—01 102.0
18.9 12.3 18.0 5.7 1.79E-01 105.7
22.3 12.5 18.2 5.7 1.79E-01 124.5
25.7 12.6 18.4 5.8 1825-01 140.8

 

 

 

 

 

 

D.1.2. Microstripline Structure #2, 1 mm i.d. discharge tube, 20 sccm

 

 

 

 

 

 

 

Pressure: 0.15 Torr
Absorbed(W) Left Right Length (cmL Vol(cm°) Density(Wcm")
0.6 5.9 8.9 3.0 2.36E-02 27.0
2.0 5.2 9.7 4.5 3.53502 57.0
4.9 4.4 10.5 6.1 4.79502 102.9
7.8 4.0 10.9 6.9 5.42502 143.0
10.8 3.7 11.3 7.6 5.97502 180.2
14.1 3.6 11.3 7.7 6.05E-02 233.8
17.5 3.3 11.7 8.4 8.80502 285.9
21.4 3.2 11.7 8.5 6.68E-02 320.8

 

 

 

 

 

 

 

121

 

Pressure: 5.0 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbed(W) Left Right Length (cm) Vol(cm3) Density(Wcm‘3)

0.8 5.6 9.2 3.8 2.83502 28.5

2.1 5.0 9.9 4.9 3.85502 55.3

5.1 4.2 10.7 6.5 5.11502 99.8

7.9 3.7 11.2 7.5 5.89502 134.5

10.9 3.4 11.5 8.1 8.38502 170.9

14.3 3.2 11.8 8.4 6.60E-02 218.7

17.7 3.4 11.5 8.1 8.38502 278.4

21.6 3.0 11.9 8.9 6.99E-02 308.8
Pressure: 10 Torr

Absorbed(W) Left Right Length (cm) Vol(cm3) Density(wcm°)

0.8 5.7 9.1 3.4 2.87502 30.2

2.1 5.0 9.9 4.9 3.85E-02 55.3

5.0 4.1 10.8 6.7 5.28502 95.8

7.9 3.6 11.3 7.7 8.05502 130.0

10.9 3.3 11.8 8.3 8.52502 188.7

14.2 3.2 11.7 8.5 8.88502 213.3

17.7 3.2 11.7 8.5 6.68E-02 285.3

21.6 3.0 12.0 9.0 7.07502 305.3
Pressure: 25 Torr

Absorbed(W) Left Right ngth (cm) Vol(cm3) Density(wcm*’)

0.9 5.7 9.2 3.5 2.75502 31.4

2.2 5.0 9.9 4.9 3.85502 58.7

5.1 4.1 10.7 6.6 5.18502 98.3

7.9 3.6 11.3 7.7 6.05E-02 131.0

10.9 3.3 11.5 8.2 6.44E-02 189.7

14.3 3.2 11.7 8.5 6.68E-02 214.1

17.7 3.2 11.7 8.5 8.88502 265.3

21.6 3.0 11.9 8.9 6.99E-02 308.8
Pressure: 50Torr

Absorbed(W) Left Right Length (cm) Vol(cm3) DensityoNcm")

0.9 5.8 8.9 3.1 2.43502 37.7

2.2 5.1 9.8 4.7 3.89502 60.7

5.2 4.3 10.6 6.3 4.95502 104.2

8.0 3.9 11.0 7.1 5.58E-02 143.1

11.0 3.5 11.4 7.9 8.20502 177.0

14.4 3.4 11.5 8.1 6.36E-02 225.8

17.8 3.4 11.5 8.1 6.36E—02 279.3

21.8 3.2 11.8 8.6 8.75502 320.4

 

 

 

 

 

 

122

 

 

 

 

 

Pressure: 100 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbed(W) Left Right Legqth (cm) Vol(cm3) Density(Wcm‘3)

1.1 5.7 9.0 3.3 2.59502 44.1

2.5 5.4 9.3 3.9 3.06E-02 80.4

5.4 4.7 10.1 5.4 4.24502 126.8

8.2 4.3 10.6 8.3 4.95502 185.8

11.2 4.0 10.9 6.9 5.42502 205.8

14.5 4.0 11.0 7.0 5.50502 283.1

18.0 4.2 10.8 6.6 5.18E-02 347.1

21.8 3.7 11.3 7.8 5.97502 384.4
Pressure: 150 Torr

Absorbed(W) Left Right Length (cm) Vol(cm3) DensigMcm‘a)

2.1 5.8 8.8 3.0 2.36E-02 90.2

5.3 5.0 9.7 4.7 3.89502 142.7

8.0 4.7 10.1 5.4 4.24502 189.4

11.0 4.4 10.4 6.0 4.71502 234.3

14.4 4.4 10.5 6.1 4.79502 299.6

17.9 4.5 10.4 5.9 4.83502 385.9

21.6 4.1 10.8 8.7 5.26E-02 411.2
Pressure:200Torr

Absorbed(W) Left Rm Length LcmL Vol(cm3) Density(wcm°)

3.7 5.7 8.9 3.2 2.51502 145.4

5.0 5.4 9.2 3.8 2.98502 168.9

8.0 4.9 9.7 4.8 3.77502 211.8

11.0 4.7 10.0 5.3 4.16E-02 263.8

14.4 4.6 10.1 5.5 4.32502 332.3

17.8 4.7 10.1 5.4 4.24502 418.9

21.6 4.4 10.4 6.0 4.71502 459.2
Pressurez300Torr

Absorbed(W) Left Right Length (cm) Vol(cm3) Density(Wcm°)

4.4 5.9 8.8 2.9 2.28502 191.7

7.5 5.4 9.2 3.8 2.98E-02 250.3

10.6 5.2 9.5 4.3 3.38E-02 313.5

14.0 5.0 9.6 4.6 3.81502 387.9

17.4 5.1 9.5 4.4 3.46E-02 504.4

21.3 4.9 9.8 4.9 3.85502 553.5
Pressure: 400 Torr

Absorbed(W) Left ﬁght Length (cm) Vol(cm3L Density(Wcm'3)

7.0 5.9 8.9 3.0 2.36E-02 295.5

10.2 5.8 9.1 3.5 2.75502 370.9

13.7 5.5 9.2 3.7 2.91502 470.7

17.0 5.5 9.1 3.6 2.83502 602.5

21.1 5.2 9.4 4.2 3.30502 638.9

 

 

 

 

 

 

123

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure: 500Torr

Absorbed(W) Left Riggt Length (cm) Vol(cm3) Density(Wcm“°’)

9.6 6.0 8.8 2.8 2.20502 438.0

13.1 5.9 8.8 2.9 2.28E-02 573.3

18.4 6.0 8.8 2.8 2.20502 748.5

20.8 5.6 9.0 3.4 2.67E-02 770.3
Pressure: 800 Torr

Absorbed(W) Left Right Length (cm) Vol(cm3) DensityMcm‘s)

12.7 5.8 8.8 3.0 2.38502 539.8
Pressure: 700 Torr

Absorbed(W) Left Right Leggth @m) Vol(cm°) Density(Wcm‘3)

12.2 6.0 8.7 2.7 2.12502 575.9

 

 

 

 

 

 

 

 

D.2 Argon - Hydrogen Discharges, microstripline structure #1, 2 mm
i.d. discharge tube, argon flow rate: 47 sccm, hydrogen ﬂow rate: 3
sccm.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure = 0.35 Torr
Absorbed Left Length
(W) (cm) nghqcm) (cm) Vol (cm‘3) PNol(WIcm*3)
3.5 14.5 16.1 1.6 5.03E-02 68.9
4.9 14.3 16.2 1.9 5.97E-02 82.7
6.9 14.1 16.3 2.2 6.91E-02 100.3
9.3 13.8 16.3 2.5 7.85E-02 118.2
13.4 13.4 17.2 3.8 1.19E—01 112.1
17.1 13.2 17.5 4.3 1.35E-01 126.4
20.1 12.9 17.6 4.7 1.48E-01 136.1
Pressure = 1.0 Torr
Absorbed Left Length
(W) (cm) ﬂghﬂcm) (cm) Vol (cm‘3) PNonLVIch‘It)
3.5 14.6 16.1 1.5 4.71 E-02 73.5
5.1 14.4 16.3 1.9 5.97E-02 85.5
6.9 14.1 16.3 2.2 6.91E-02 100.3
9.3 13.9 16.4 2.5 7.85E-02 118.2
13.2 13.5 17.1 3.6 1.13E—01 116.8
16.6 13.3 17.4 4.1 1.29E-01 128.7
19.9 12.9 17.6 4.7 1.48E-01 134.9

 

124

 

 

 

Pressure = 2.0 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbed Left Length
(W) (cm) Rllhucm) (cm) Vol (cm‘3) PNoI(WIcm*3)
3.6 14.6 16.0 1.4 4.40E-02 82.6
5.3 14.5 16.3 1.8 5.65E-02 93.3
6.9 14.3 16.4 2.1 6.60E-02 105.0
9.5 14.0 16.4 2.4 7.54E-02 125.4
13.4 13.6 17.2 3.6 1.13E-01 118.3
16.6 13.3 17.4 4.1 1 .29E-01 128.7
19.9 13.0 17.6 4.6 1.45E-01 137.9
Pressure = 3.0 Torr
Absorbed Left Length
(W) (cm) nghucm) (cm) Vol (cm‘3) PNoI(WIcm‘3)
3.5 14.6 16.1 1.5 4.71E-02 73.5
4.9 14.5 16.3 1.8 5.65E-02 87.3
6.9 14.3 16.3 2.0 6.28E-02 110.3
9.3 14.0 16.4 2.4 7.54E-02 123.2
13.0 13.6 17.2 3.6 1.13E-01 115.3
16.6 13.3 17.4 4.1 1.29E-01 128.7
19.9 13.1 17.6 4.5 1.41E—01 140.9
Pressure = 5.0 Torr
Absorbed Left Length
(W) (cm) Righﬂcm) (cm) Vol (cm‘3) PNoI(WIcm*3)
3.5 14.7 16.1 1.4 4.40E-02 76.8
4.9 14.5 16.2 1.7 534502 92.4
6.9 14.3 16.3 2.0 6.28E—02 110.3
9.3 14.0 16.3 2.3 7235-02 128.5
13.0 13.6 17.1 3.5 1.10E-01 118.6
16.6 13.4 17.4 4.0 1.26E-01 131.9
19.9 13.1 17.6 4.5 1.41E—01 140.9
Pressure = 10.0 Torr
Absorbed Left Length
(W) (cm) Righqcm) (cm) Vol (cm‘3) PNol(WIcmL3)
5.1 14.5 16.2 1.7 5.34E-02 95.6
6.9 14.4 16.3 1.9 5.97E-02 116.1
9.3 14.1 16.3 2.2 6.91E-02 134.3
11.7 13.9 16.4 2.5 7.85E-02 148.8
16.6 13.6 17.3 3.7 1.16E-01 142.6
19.8 13.3 17.6 4.3 1.35E-01 146.2

 

 

 

 

 

 

125

 

 

 

 

 

 

Pressure = 15.0 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbed Left Length
(W) (cm) Righucm) (cm) Vol (cm‘3) PNoI(WIcm*3)
5.3 14.6 16.1 1.5 4.71E-02 111.9
6.9 14.5 16.3 1.8 5.65E-02 122.5
9.3 14.3 16.3 2.0 6.28E-02 147.8
11.7 14.0 16.4 2.4 7.54E-02 155.0
16.6 13.7 17.0 3.3 1.04E-01 159.8
20.3 13.4 17.3 3.9 1.23E-01 165.4
23.1 13.3 17.4 4.1 1.29E-01 179.5

Pressure = 20.0 Torr

Absorbed Left Length
(W) (cm) Rllhucm) (cm) Vol (cm‘3) PNoI(WIcm*3)
5.2 14.4 16.0 1.6 5.03E-02 104.2
7.3 14.3 16.1 1.8 5.65E-02 128.4
9.7 14.0 16.2 2.2 6.91E-02 139.8
12.5 13.8 16.3 2.5 7.85E-02 159.4
17.6 13.4 16.9 3.5 1.10E—01 159.7
21.4 13.1 17.3 4.2 1.32E-01 162.4

Pressure 8 25.0 Torr

Absorbed Left Length
(W) (cm) RIght(cm) (cm) Vol (cm‘3) PNoI(WIcm*3)
3.8 14.5 16.0 1.5 4.71E-02 80.1
6.0 14.4 16.0 1.6 5.03E-02 119.8
8.3 14.2 16.1 1.9 5.97E-02 139.2
11.1 14.0 16.2 2.2 6.91E—02 159.9
13.6 13.7 16.3 2.6 8.17E-02 166.7
19.2 13.2 17.2 4.0 1.26E-01 152.6

 

 

 

 

 

 

 

D.3 Pure Hydrogen Discharges, microstripline structure #1, 2 mm i.d.

discharge tube, 5 sccm.

 

Pressure = 0.34 Torr

 

 

 

 

 

 

 

 

Absorbed Left Length
(W) (cm) ﬁghtmm) (cm) Vol 1cm”) PNol(WIcm“3)
3.6 14.9 16.0 1.1 3.46E—02 105.1
5.3 14.9 16.1 1.2 3.77E-02 139.9
7.1 14.8 16.2 1.4 4.40E-02 161.4
9.1 14.7 16.2 1.5 4.71E-02 193.5
11.3 14.7 16.3 1.6 5.03E—02 225.8
14.2 14.6 16.3 1.7 5.34E-02 266.0
16.2 14.5 16.4 1.9 5.97E—02 271.5

 

126

 

 

 

 

 

Pressure = 1.0 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbed Left Length
(W) (cm) Righicm) (cm) Vol (cm‘3) PNol(WIcm*§)
5.3 14.8 16.2 1.4 4.40E—02 119.9
6.9 14.7 16.2 1.5 4.71E-02 147.0
8.9 14.7 16.3 1.6 5.03E—02 178.0
11.0 14.6 16.2 1.6 5.03E-02 219.1
13.7 14.6 16.3 1.7 5.34E—02 256.5
15.9 14.5 16.3 1.8 5.65E-02 280.6

- Pressure = 2.0 Torr

Absorbed Left Length
(W) (cm) Right(cm) (cm) Vol (cm’t3) PNoI(WIcm"3)
5.3 14.8 16.1 1.3 4.08E-02 129.2
6.8 14.7 16.2 1.5 4.71E-02 143.5
8.6 14.7 16.3 1.6 5.03E—02 171.3
10.8 14.7 16.3 1.6 5.03E—02 215.7
13.5 14.6 16.3 1.7 5.34E-02 253.4
15.9 14.6 16.3 1.7 5.34E—02 297.1

Pressure = 5.0 Torr

Absorbed Left Length
(W) (cm) Righucm) (cm) Vol (cm‘3) PNoI(WIcm“3)
6.6 14.9 16.1 1.2 3.77E-02 174.8
8.6 14.8 16.2 1.4 4.40E-02 195.8
11.0 14.7 16.2 1.5 4.71E-02 233.7
13.5 14.7 16.3 1.6 5.03E-02 269.2
15.9 14.7 16.3 1.6 5.03E-02 315.7

Pressure = 10.0 Torr

Absorbed Left Length
(W) (cm) ﬁghﬂcm) (cm) Vol (cm‘3) PNoI(WIcm*3)
8.6 14.8 16.0 1.2 3.77E-02 229.4
11.3 14.7 16.0 1.3 4.08E—02 277.6
13.8 14.7 16.1 1.4 4.40E-02 314.7
16.4 14.6 16.1 1.5 4.71E-02 347.2

 

 

 

 

 

 

127

 

 

 

 

D.4 Pure Nitrogen Discharges, microstripline structure #1, 2 mm i.d.
discharge tube, 5 sccm.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pressure = 0.0 Torr

Absorbed Left Length
(W) (cm) Righqcm) (cm) Vol (cm‘3) PNoI(WIcm*3)
3.9 5.9 7.2 1.3 4.08E-02 96.1
5.6 5.9 7.2 1.3 4.08E-02 136.6
7.6 5.8 7.2 1.4 4.40E-02 172.7
9.7 5.8 7.3 1.5 4.71E-02 205.0
12.2 5.8 7.3 1.5 4.71E-02 258.5
15.0 5.7 7.3 1.6 5.03E-02 298.9
17.7 5.7 7.3 1.6 5.03E—02 352.4

Pressure a 0.50 Torr

Absorbed Left Length
(W) (cm) Mom) (cm) Vol (cm‘3) PNoI(WIcm*3)
3.6 6.0 7.2 1.2 3.77E—02 95.1
5.4 5.9 7.2 1.3 4.08E-02 132.4
7.6 5.8 7.3 1.5 4.71E-02 161.2
9.7 5.8 7.3 1.5 4715-02 205.0
12.2 5.8 7.4 1.6 5.03E-02 242.3
15.0 5.7 7.4 1.7 5.34E-02 281.3
18.1 5.7 7.4 1.7 5.34E-02 338.0

Pressure = 1.0 Torr

Absorbed Left Length
(W) (cm) nght(cm) (cm) Vol (cm‘3) PNol(WIcm“3)
3.6 5.9 7.2 1.3 4.08E-02 87.8
5.2 5.9 7.3 1.4 4.40E-02 119.1
7.3 5.8 7.3 1.5 4.71E-02 154.0
9.5 5.8 7.3 1.5 4.71E-02 201.4
12.2 5.8 7.4 1.6 5.03E-02 242.3
15.5 5.7 7.4 1.7 5.34E-02 290.8
18.4 5.7 7.4 1.7 5.34E-02 344.3

Pressure = 2.0 Torr

Absorbed Left Length
(W) Em) @ghﬂcm) (cm) Vol (cm‘3) PNol(WIcm*3)
3.6 5.9 7.2 1.3 4.08E-02 87.8
5.1 5.9 7.3 1.4 4.40E—02 115.3
7.4 5.8 7.3 1.5 4.71E—02 157.6
9.5 5.8 7.4 1.6 5.03E—02 188.8
12.5 5.7 7.4 1.7 5.34E—02 234.4
15.9 5.7 7.4 1.7 5.34E-02 297.1
18.9 5.7 7.4 1.7 5.34E—02 353.8

 

 

 

 

 

 

128

 

 

Pressure = 3.0 Torr

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absorbed Left Length
(W) 1m) nghucm) Jegm) Vol (cm‘3) PNoI(WIcm“3
2.9 6.0 7.2 1.2 3.77E—02 77.2
4.9 5.9 7.2 1.3 4.08E-02 120.0
7.1 5.9 7.3 1.4 4.40E-02 161.2
9.2 5.8 7.3 1.5 4.71E-02 194.3
11.8 5.8 7.4 1.6 5.03E-02 235.6
15.2 5.7 7.4 1.7 5.34E-02 284.5
18.1 5.7 7.5 1.8 5.65E-02 319.2
Pressure = 5.0 Torr
Absorbed Left Length
(W) (cm) Rmhucm) (cm) Vol (cm‘3) PNoKWIcm‘3)
4.9 5.9 7.2 1.3 4.08E-02 120.0
7.1 5.9 7.3 1.4 4.40E-02 162.5
9.4 5.8 7.3 1.5 4.71E-02 200.2
11.6 5.8 7.3 1.5 4.71E-02 246.5
14.2 5.8 7.4 1.6 5.03E-02 282.1
15.8 5.8 7.4 1.6 5.03E—02 314.3
Pressure = 10.0 Torr
Absorbed Left Length
(W) (cm) Rjghucm) (cm) Vol (cm‘3) PNoKWIcm‘3)
7.7 5.9 7.2 1.3 4.08E-02 188.0
9.1 5.9 7.3 1.4 4.40E-02 207.2
11.9 5.8 7.3 1.5 4.71E-02 251.6

 

 

 

 

 

 

129

 

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[20] Y. M. Aliev, H. Schulter, and A. Shivarova, Guided-Wave-Produced Plasmas,
Springer, Berlin, 2000.

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