Monte Carlo simulation of neutral-beam injection for mirror fusion reactors

Energetic neutral-beam particles interact with the target plasma through electron-atom and ion-atom collisional ionization as well as ion-atom charge-transfer (charge-exchange) collisions to give a fractional trapping of the neutral beam and a loss of charge-transfer-produced neutrals which escape to bombard the reactor first wall. Appropriate interaction cross sections for these processes are calculated for the assumed anisotropic, non-Maxwellian plasma ion phase-space distributions. The target plasma is assumed to be confined by a Yin-Yang mirror-coil configuration and has distinct radial and axial density profiles as modeled in steady-state and three spatial dimensions. The energy and angular distributions of a population of neutral test particles are computed to give statistical estimates of neutral-beam trapping efficiency, non-uniform first-wall surface heating rates and first-wall sputtering-erosion for use in engineering-design calculations. A guide to the NUBIN computer is included.