Electron beam disruption due to ion release from targets-comparison between computer calculations and observations

Summary form only given, as follows. Experiments have been performed on the first axis of the DARHT electron beam accelerator to study the effects on the beam of ion emission from surfaces struck by electrons. Calculations using the two-and three-dimensional Lsp particle-in-cell code were performed to compare with experimental results. Two-dimensional calculations, which allow the release of ions when the impacted surface temperature increases by 400 K accurately replicate experimental results showing beam blow-up downstream of the surface just after ion emission. Three-dimensional calculations show the onset of a hose instability after beam blow up in agreement with observations. The frequency of this instability indicates a large component of H/sup +/ ions, which may come from the "cracking" of desorbed water. Calculations in support of experiments to identify the desorbed species are presented.