  The cyclotron gas stopper is a newly proposed device to stop energetic rare
isotope ions from projectile fragmentation reactions in a helium-filled
chamber. The radioactive ions are slowed down by collisions with a buffer gas
inside a cyclotron-type magnet and are extracted via interactions with a Radio
Frequency (RF) field applied to a sequence of concentric electrodes (RF
carpet). The present study focuses on a detailed understanding of space charge
effects in the ion extraction region. The space charge is generated by the
ionized helium gas created by the stopping of the ions and eventually limits
the beam rate. Particle-in-cell simulations of a two-component
(electron-helium) plasma interacting via Coulomb forces were performed in the
space charge field created by the stopping beam.
