Beam divergence in magnetically-insulated ion diodes

Summary form only given. A number of experimental investigations of divergence in applied-B magnetically insulated ion diodes have recently been carried out at Sandia National Laboratories, Cornell University, and Kernforschungszentrum Karlsruhe Germany. Several important conclusions can be drawn about the phenomenonology of beam divergence in these devices. The observations generally agree well with ideas developed from theoretical investigations and numerical simulation by researchers at Sandia and Cornell, which suggest mechanisms of divergence growth due to ion and electron dynamics in the diode accelerating gap. The possible effects on divergence of the anode plasma which supplies ions to the gap are perhaps less well understood at present. The author argues that anode plasma effects are important in minimizing beam divergence. New observations on the Lion divergence experiment at Cornell also suggest strongly that anode plasma conditions are implicated in the so-called "parasitic load", which is observed to divert a substantial fraction of the diode current from the beam in many high-power ion diodes.