A Comprehensive Particle-In-Cell Model for Microwave-Based Ion Source Optimization*

SHINE Technologies, LLC currently utilizes beam-target based fusion devices to produce neutrons. The components that constitute these neutron generators are purpose-built for long-duration operation, and significant investments have been made to ensure their high reliability. To minimize maintenance of system components, further improvements are desired. Achieving these improvements requires a deep understanding of the microwave-driven plasma that acts as an ion source. In this work, we present a comprehensive Particle-In-Cell (PiC) model of SHINE's microwave-based ion source, aimed at investigating the coupling dynamics between the plasma and the chamber wall under various conditions. Our study includes detailed comparisons between the model's predictions and empirical data, such as total output current, crosswire scanner data, and emittance measurements obtained from a low energy beam transport test stand. The primary objective of both the measurements and the modeling campaign is to understand the heating mechanisms, spatial distribution of the plasma in the steady state, and its stability in response to perturbations. The modeling campaign includes a systematic exploration of system parameters, providing valuable insights into the behavior and optimization of microwave-based ion sources.