High current density magnetically insulated H- diodes

At the University of California, Irvine (UCI), we have been studying the production of intense H- beams using pulse power techniques for the past 7 years. Recently, we have developed diodes similar to the coaxial design of the Lebedev Physical Institute, Moscow, where current densities of up to 200 A/cm2 were reported using nuclear activation of a carbon target. In experiments at UCI using the machine APEX, a 1 MV, 50 ns, 7 Ω pulseline, and the coaxial diode geometry, current densities of up to 35 A/cm2 from a passive polyethylene cathode loaded with TiH2 have been measured using a pinhole camera and CR-39 track recording plastic. We have also begun work on a planar diode which can generate a directed beam of H- ions. The cathode also uses TiH2 loading of a polyethylene substrate and the APEX has been modified to include an external LC circuit which can generate a bipolar, 125 kV, 1 μs duration prepulse (similar prepulse characteristic as in the Lebedev Institute experiments cited above) for plasma production