Effect of electron energy distribution function in plasma and energy dispersion of electron beam on the stability of a low-voltage beam discharge

A kinetic approach is used in the study of the conditions for instability of a low-voltage beam discharge in inert gases versus electron beam temperature, velocity dispersion of beam electrons along the discharge axis, and electron energy distribution function (EEDF). Regimes in which the interelectrode distance is on the order of the electron mean free path with respect to elastic collisions with inert-gas atoms are considered. It is shown that beam temperature $T_b$ that is determined in the low-voltage beam discharge by the cathode temperature, which is no greater than 1500 K, and energy dispersion of beam electrons, which can be significantly greater than $kT_b$ in such a discharge and amount to 1–2 eV, weakly affect the conditions for stability loss and an increment of perturbation growth at frequencies of up to the plasma frequency. It is found that the EEDF that monotonically decreases with increasing electron energy also does not affect parameters of perturbations that propagate in the low-voltage beam discharge at a beam energy that is significantly greater than the mean energy of electrons in plasma. The results obtained for the specified discharge can also be used for alternative self-sustained beam discharges.