Micropinches in plasma flame expanding into vacuum ambient

Abstract

Results of experimental and theoretical studies of plasma parameters in a current-carrying plasma flame expanding into the vacuum ambient are presented. It is shown that at the initial stage of the discharge burning the short-run beams of multiply charged ions of the cathode material (with mean ion charge state up +9 for Cu) were emitted from the cathode plasma flame. The X-ray pinhole measurements showed that a small-size area of hot electron with a temperature of 100 ÷ 200 eV was formed at a range of about 2÷3 mm from the cathode. A theoretical model is developed of the process of the current-carrying cathode plasma flame expansion. A set of hydrodynamic equations was solved numerically by the particle-in-cell method. It was shown that due to the Ampere forces a neck was formed at a distance from the cathode that was developed to a micropinch, where electron temperature attained of about 100 eV and the beams of multiply charged ions of the cathode material were produced. Both the temporal and space parameters of the micropinch formation are consistent with results of the measurements. The mean ion charge state of the ions also is in agreement with the experimental data.