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Savard, Nicolas

University of British Columbia

Penning ion sources are relatively inexpensive and compact ion sources, and therefore could be used to replace costly Electron Cyclotron Resonance ion sources for high current alpha-particle production in medical accelerators. To be able to optimize a Penning ion source for high current alpha-particle production, one first needs to be able to characterize and understand the plasma dynamics within it under helium operation. For this reason, a test stand and prototype Penning ion source is developed which allows for the confining magnetic field (0.1 - 0.9 T), inlet helium gas flow (5-25 sccm), arc voltage (1 - 2 kV), and extraction voltage (≤ 15 kV) of the ion source to vary. This thesis describes the design and engineering of the Penning ion source using helium gas. In addition, plasma simulations using COMSOL Multiphysics™, are used to model how this ion source responds to various input parameters, and diagnostics tools such as optical emission spectroscopy are used to measure the plasma properties as these parameters are varied. The latter was done by creating a collisional-radiative model which compares well with Yacora on the Web from IPP Garching and improves upon it by adding radiation trapping approximations. The optical emission spectroscopy diagnostic is compared to Langmuir probe measurements in a TRIUMF-licensed Volume Cusp ion source to verify trends observed using this diagnostic. It is found that the plasma simulations and optical emission spectroscopy diagnostics agree on observed trends of electron and ion density for each varied operational parameter. This is confirmed by observing the same trends when extracting the He⁺ ions from the ion source. However, it is clear that the non-Maxwellian behavior of electrons can have a significant effect on plasma dynamics, which cannot be resolved with the current diagnostics or plasma models. Thus future studies will need to be performed to analyze the electron kinetics within the plasma to better determine how alpha particle density changes as a function of the various input parameters, and thus how to optimize the ion source for alpha production.

Text

2022-04-07

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/81120

Physics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/