Dynamics of the Electron Energy Distribution Function in the Gas-Discharge Channel of a Single-Stage Plasma Thruster with Anode Layer

Abstract

Results of experimental studies of local plasma parameters in the gas-discharge channel of a model single-stage plasma thruster with an anode layer (TAL) are presented. The electron energy distribution function and its dynamics along the middle line of the channel are determined. It is found that, as in a similar stationary plasma thruster (SPT), there are three groups of electrons: low-speed electrons with energies of about 8–12 eV, high-speed electrons with energies of 40–50 eV, and a relatively small group of electrons with intermediate energies. The experiments have shown that the generation regions and dynamics of these groups of electrons in the TAL under study differ from those in the SPT. The energy characteristics of the low-speed electron component are calculated and the dynamics of the high-speed and intermediate groups of electrons are analyzed according to the technique developed for SPTs. It is shown that, in the single-stage TAL, in contrast to the SPT, the condition of global isodrift over the entire channel is not satisfied and the zones of gas ionization and ion acceleration are separated more clearly. The generation region of high-speed electrons in the TAL under study differ from that in the SPT; however, the position of the peak of the energy distribution function of this group, as in the SPT, depends linearly on the plasma potential. As is commonly accepted by experts in SPTs, the appearance of the intermediate group of electrons is not related to the presence of the dielectric channel wall and finite near-wall conductivity.