Propagation characteristics of intense relativist-ic electron beam

Abstract

The design and testing results of a small and versatile pulsed system "SNU" are described. This machine has a 3 KJ, 600 KV, 12 stages Marx generator that charges 6.8 ohm water filled pulseforming line, which is then connected to a load through a self breakdown spark switch. The triggering characteristics of Marx generator is shown to be very stable and output reproducibility is also fairly good. This peaked pulse generator is designed to be versatile in output parameters of polarity, pulse length and impedance. It is shown that the energy conversion efficiency of "SNU" versatile electron beam accelerator from the Marx generator to the electron beam is reached up to about 63% in a condition where the $N_2$ gas pressures of Marx and pulse line switches are 0.3 Kg/㎠ and 3 Kg/㎠ , respectively, and the vacuum of diode chamber is $1.3×10^{-2}$ Torr. The steady-state one dimensional theoretical model of the intense relativistic electron beam propagation within the vacuum diode and its numerical results are presented. The characteristic curves of injection current density and its beam radius are exactly obtained as a function of the diode voltage. The experimental investigation of intense relativistic electron beam propagation in vacuum diode has also been reported. The beam current rises to its peak value 30 KA in about 60 nsec, which is nearly same as pulse width, and then decayed without any positive part of tail oscillation. It is shown that the virtual cathode is not formed in vacuum diode regime from the both theoretical and experimental results. The steady-state equilibrium properties of bipolar electron and ion flow in a relativistic planar diode were calculated within the framework of the cold-fluid-Poisson equations. An exact analytic solution for the electron current density was obtained in terms of diode voltage, the anode-cathode gap and the parameter of ion current. It was found that ion presence in the diode significantly enhances the electron current, a...