Speaker
Description
High-current compact cyclotrons face strong space-charge limitations during axial injection, where the low-energy proton beam expands before reaching the inflector. We present a novel plasma-assisted neutralization module designed as a drop-in element between the final solenoid and the inflector entrance. The device consists of a short solenoid surrounding a beamline cell operated at controlled pressure. Residual hydrogen gas $(H_2)$ or an injected noble gas $(Kr)$ is ionized by the high-current proton beam to form a self-sustaining plasma column. Biased end-electrodes confine electrons and accelerate neutralization, achieving effective space-charge compensation. Krypton seeding provides a faster build-up of neutralization relative to $H_2$, enabling rapid stabilization for pulsed or ramped operation. Simulations and analytic estimates indicate that neutralization substantially reduces transverse beam blow-up while introducing only modest multiple scattering over the short transport distance. The concept offers a compact, plasma-based method to increase capture efficiency for milliampere-class proton beams and provides a tunable platform to investigate plasma–beam interaction effects in cyclotron injection lines. Initial design parameters, integration strategy, and predicted performance are presented.
Funding Agency
This research was supported by the National Research Foundation of Korea (NRF) grants funded by the Ministry of Education (MOE) (Grant No. RS-2023-00250346).
