Particle monitor probe: a novel tool for fast plasma diagnostics and space charge compensation investigation in high-intensity proton accelerators

Advanced plasma diagnostics are crucial for optimizing high-intensity accelerators, particularly for ion source characterization and understanding transient phenomena such as space charge compensation (SCC). This work introduces a novel, cost-effective Particle Monitor Probe (PMP) designed for versatile plasma diagnostics in such demanding environments. The PMP's capabilities have been established through a combination of Particle-in-Cell/Monte Carlo Collision simulations and comprehensive experimental validation on the Low Energy High Intensity Proton Accelerator (LEHIPA). Time Domain Reflectometry measurements confirmed the PMP's fast temporal response of approximately 22 ns, enabling the resolution of microsecond-scale plasma dynamics. The probe demonstrated successful remote characterization of Electron Cyclotron Resonance ion source plasma, with observed plasma fluctuations directly correlating with extracted beam properties, thereby providing a valuable tool for source optimization. Furthermore, the PMP enabled quantitative measurements of SCC time in the LEHIPA Low Energy Beam Transport line. These measurements, showing SCC time decreasing with increasing residual gas pressure and eventually saturating, are consistent with theoretical predictions and simulation results. The PMP's biasing capability also allows for the differentiation of charged particle species. The developed PMP thus represents a significant advancement, offering a simple, robust, and sensitive diagnostic for enhancing the understanding and performance of ion sources and low-energy beam transport in high-intensity accelerator systems. *E-mail: pallavip@barc.gov.in.