Dependence of the Generation Rate of High-Energy Electrons in Helium on the Electron Angular Scattering Model

It is known that in dense gases in sufficiently strong electric fields, electrons can be continuously accelerated, when they receive more energy from the field than is lost in collisions with atoms and molecules of the medium (runaway electrons). In this work, we study the effect of electron angular scattering in elementary ionization and excitation acts of atoms on the acceleration of electrons in strong fields. To this end, a computer code is developed on the basis of the Monte Carlo technique, and the kinetics of electrons in helium is numerically simulated. In the setting corresponding to the configurations of laboratory experiments with electron “swarms,” the code is tested by comparing the calculated kinetic characteristics of the electron swarm (ionization coefficient, drift velocity) with the measurement data in different types of experiments. Numerical simulation is performed for a gas of motionless helium atoms with a concentration N equal to the Loschmidt number $${{N}_{{\text{L}}}} = 2.69 \times $$ 1019 cm–3, in the fields with the strength E from 50 to 300 kV cm–1. The generation rate νhe of electrons with energies in the range from 0.25 to 10 keV is calculated, which is recommended for the use in a source of high-energy electrons in problems of the numerical simulation of gas discharges developing in strong electric fields with the participation of runaway electrons. It is shown that different models of electron anisotropic scattering in inelastic interactions with atoms can lead to multiple differences in the rate νhe values.