Hybrid simulation of high-power ion beam transport and beam focusing through a gas chamber

Summary form only given. The CIDER two-dimensional hybrid code has been used to simulate high-power ion beam transport and focusing in the gas cell of a light ion beam accelerator, such as PBFA II (Particle Beam Fusion Accelerator II). The CIDER hybrid code treats the ions in the beam and in background plasma as particles, and the electrons as a collisional fluid. The simulation model includes important features and essential physics of the ion beam propagation in the gas chamber. They are: (i) cylindrical geometry of the gas cell; (ii) proper entry conditions for a converging ion beam; (iii) realistic magnetic configuration due to external cathode and anode current coils; (iv) multiple scattering of beam ions with the gas molecules; (v) multi-ion species in the beam; and (vi) electron emissions from the chamber walls. The issues of current neutralization and charge neutralization of a converging ion beam have been studied. Beam divergence as a consequence of insufficient neutralization has been explored. In addition, the electrons constitute a finite beta fluid which alters the topology of the applied magnetic field and can affect the beam propagation as a whole