Numerical studies of ion-focused transport in a recirculating accelerator

In Ion-Focused Transport (IFT), an intense electron beam is injected onto a preformed, low-density plasma channel, and expels the plasma electrons. The resulting ion column focuses the beam. A numerical study of the application of IFT to recirculating accelerators is presented. A 3-D simulation of beam injection into a curved channel shows beam erosion at close to the predicted rate. During induction-gap acceleration, both the beam and channel are found to shrink in radius, thereby increasing the focusing force on the beam, and reducing the loss of particle due to centrifugal force. Finally, simulations of the ion-resonance instability show the theoretically predicted growth rate. In the absence of stabilizing measures, the instability leads to strong disruption of the beam and channel