Charge stripping is an increasingly necessary process in ion accelerators, particularly those which are used in accelerating high mass nuclei such as uranium. Generally in accelerator facilities, heavy ions are produced in the ion source with a relatively low charge state distribution. In the charge stripper, further removal of electrons from the ion beam enables greater energy gain in accelerating cavities downstream of the charge stripper, which can lower cost of attaining a desired energy. For this reason the charge stripper is typically located early in the accelerator. The ion acceleration community is met with an increasingly strong demand for higher particle counts in the ion beams because facility users almost always can benefit from higher statistics in their experiments. This means higher beam intensities. This need for higher intensity presents the challenge of preventing traditionally employed solid charge strippers, like diamond-like carbon (DLC) foils, from suffering overwhelming kinetic impact damage from the beam and reducing or eliminating their charge stripping function. These issues are even more critical when stripping heavy ions because of their much larger energy deposition per unit length compared with protons or low mass heavy ions. This high energy deposition results from a sharper Bragg peak for heavier ions.Alternatively, gas charge strippers do not suffer from this kind of irreparable degradation, but do present a host of other unique challenges. Chief among these challenges is confining the gas to only a small segment of the beamline and preventing it from excessively leaking to other upstream and downstream components of the beamline whose performance can be hindered or entirely prevented by pressures above 10-7 torr. The plasma window (PW) device is one which can limit the flow of gas from a high pressure gas charge stripping chamber (GCS) to the surrounding low pressure beamline - without the need for any solid interface, that would likely be damaged or destroyed by the ion beam. The PW is a direct current (DC) cascaded arc which heats and ionizes the gas flowing out of the GCS, thereby restricting the flow by greatly reducing the density of the gas flow. One would be located on both ends of the GCS. The degree to which this limits the gas flow depends on the temperature attained within the arc, which primarily depends upon the pressure maintained in the GCS and the arc current. These parameters are the operating conditions which can be user-controlled in a fixed-geometry PW to tune its utility. In addition, the PW performance depends on its geometry, both its channel radius and channel length. Both helium and argon are studied, each having pros and cons for potential gas charge stripper applications which will be summarized. Within the operating conditions and geometry studied in this thesis, the PW can reduce the gas flow escaping from the GCS by a factor of up to about 24 in argon and 15 in helium.The goal of the work summarized in this thesis was to quantify the utility of the PW in reducing the gas leakage rate from the gas charge stripper in a variety of operating conditions, and to gain an understanding of the mechanisms involved in effecting the flow rate reduction. Design recommendations for a next generation PW are also given to address persisting challenges with employing it in tandem with a GCS for ion beams. This work shows that a PW-based gas charge stripper system may be effective for future high intensity ion accelerators. To get to that point, more work is necessary to extend the continuous, uninterrupted lifetime of the plasma window.
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