MICROSECOND OPERATION OF A GENERAL-PURPOSE PULSED PROTON GUN

A magnetically insulated pulsed proton gun is described that provides an extracted parallel beam of annular cross section for microsecond pulse lengths. In initial tests, time-averaged currents of 5 kA and current densities of 50 A/cm2 were achieved with ≲200 kV voltage. The behavior of the gun appears to be determined by instabilities of the cathode electron cloud growing over time scales of the order of 0.5 msec to give ion current-density enhancements greater than a factor of 50 above the Child-Langmuir limit.