Intense Relativistic Electron Beam Diode in Presence of Prepulse

Intense relativistic electron beam diode has been operated without a prepulse switch. A bipolar prepulse of peak 60 kV voltage has been recorded at the diode voltage. Prepulse generated plasma expands and lowers the impedance of the diode. For small gap prepulse generated plasma completely fills the anode cathode gap and the diode behaves as plasma filled diode. It has been observed that electron beam can be generated without encountering the closure problem if the anode cathode gap is kept larger than that estimated by the Child Langmuir relation. At a large gap the beam parameters obtained are 420 KeV, 22 kA, 100 ns. Intense electron beam diode behavior was studied for various anode cathode gaps and voltages in presence of prepulse. From the experimentally obtained values of perveance an upper limit was set up for the Marx voltage (or anode cathode voltage) and lower limit for the anode cathode gap in order to avoid the gap closure problem and the diode can be operated with a better shot to shot reproducibility.