Generation of GW VHF power pulses with a magnetically swept e beam and inverse e beam diodes

Abstract

The concept of converting a multi-kA relativistic e beam into an ultrahigh-power rf pulse with a magnetically swept e-beam switch is studied. Two short VHF pulses are created by rapidly switching a 60-ns, 900-keV, 15-kA e beam between a pair of inverse e-beam diodes. The switching is done by a transverse 500-G, sinusoidal B field, oscillating at 50 MHz. The e-beam pulses are transported 1.6–4.6 cm in vacuum and ballistically or magnetically focused onto the collectors of the inverse diodes. The inverse diodes extract electrical energy from the deflected e-beam pulses and transport the energy to resistive loads that varied between 30 and 130 Ω. Numerical simulations of the e-beam transport with self-electric and magnetic fields are performed that show the sources of electrical inefficiency. These occur because the e beam is near the space-charge limit during transport. Peak unipolar powers of 2.0 and 0.5 GW are coupled to the resistive loads for the ballistically and magnetically transported e-beam geometries, respectively.