Plasma Formation in a Neutral Gas by a Short-Pulsed, High-Current Electron Beam

Numerical investigations were made of plasma formation in the interaction of an electron beam (600 kV, 10 kA peak, 3 ns FWHM) with a neutral gas (0.8–8 Torr Ar). In the numerical model, the beam is assumed to be a rigid cylindrical rod, and the plasma formation processes are assumed as follows: initially, high-energy beam-electron impact ionizes the gas, and the space-charge electric field of the beam is neutralized by the ions produced. Then, the beam-induced axial electric field becomes dominant, causes gas breakdown, and drives the plasma current. A plasma of density ∼10 14 cm -3 and temperature ∼5 eV is produced in the beam-gas interaction. The numerical results approximately agree with the experimental ones for the plasma current and for the singly-ionized line emission.