Ions acceleration by virtual cathode at plasma injection

Abstract

Summary form only given. Ion acceleration in the first section of a collective ion accelerator was studied experimentally. The first section was destined for low frequency modulation of supercritical intense relativistic electron beam (REB) current due to periodic compensation of a virtual cathode (VC) by plasma ions and for formation of ion flow in the VC electric field. In the second section with a periodic magnetic field the ions should be accelerated by a space charge wave arising at REB modulation both in time and space. The external plasma was produced by 4 plasma guns placed equidistantly on peripherals of the drift tube in the VC region. The configuration of created plasma and its parameters - density, temperature, flow speed and density dependence on time - were measured by the electrical probe. By changing the place of the electrodynamics jump of the drift tube the VC location was varied relative to the plasma source. The dielectric screens prevented plasma motion to the diode and axial area. The optimization of low frequency modulation and ion flow was achieved by time delay of REB injection with respect to plasma source switching. Low frequency modulation was measured by Faraday cup and X-ray sensor. The ions were registered by track detectors made from cellulose nitrate, and ion energy was determined by a time-of-flight analyzer. Low frequency modulation with depth 10% at frequency 46 MHz was obtained. The optimum time delay for maximum output of accelerated ions with energy 0.54 MeV exceeded that caused by acceleration in the VC potential well.