Three-dimensional, particle-in-cell simulations of applied-B ion diodes on the particle beam fusion accelerator II

We have used the three-dimensional, particle-in-cell code QUICKSILVER [J. P. Quintenz, et al., Lasers and Particle Beams 12, 283 (1994)] to simulate radial applied-B ion diodes on the particle beam fusion accelerator II at Sandia National Laboratories. The simulations agree well with experiments early in the beam pulse, but differ substantially as the ion-beam current increases. This is attributed to the oversimplified ion emission model. We see the same instabilities seen in earlier simulations with idealized diode geometries; Early in time there is a diocotron instability, followed by a transition to an ‘‘ion mode’’ instability at much lower frequency. The instability-induced beam divergence for the ∼10 MeV beam during the diocotron phase is