PiC/MC-simulation of a low-pressure discharge in helium initiated by a relativistic electron beam in a coaxial chamber with a magnetic cusp

Abstract

A gas discharge is simulated and numerically studied. The discharge is excited by a tubular relativistic electron beam in gaseous helium in a coaxial gas-discharge chamber. A magnetic field in the form of a cusp was imposed on the chamber. The code based on the PiC/MC-method was used. Electron beam dynamics, time evolution of phase portraits of particles, physical parameters, and spatial-time characteristics of plasma were calculated. It is shown that a dense plasma appears in the cavity under the action of an electron beam in the form of a thin-walled tube of a large length; its concentration can be nHe+≈2×1010 cm−3. At the same time, it turned out that plasma is considerably non-uniform in length; its denser part corresponds to the parts where beams stop. Time dependence of the charge compensation of electrons on the helium atom concentration in the chamber was calculated. The dependence turned out to be decreasing since the rate of the discharge development is increasing with the growth of the helium pressure in the cavity.