Kinetic modelling of non-equilibrium air plasma generated by energetic photon and electron beam

Abstract

The general context of this research work is about the study of electromagnetic perturbations on electronic devices due to an X-ray flash and the air plasma-induced electromagnetic field. The latter needs a good knowledge of the main processes responsible of the formation, the recombination and the relaxation of the non-equilibrium air plasma generated by energetic photons and electrons. A 0D chemical kinetic model has been developed to analyze temporal evolution of an air plasma generated by an initial energetic X-ray flash having a sin4 (t) profile with a mean energy of 1 MeV and a maximum at 50 ns. The kinetic model considers 19 selected influent species (electrons, positive and negative ions, metastables and neutral atoms or molecules) reacting following 126 reactions. The initial gas at atmospheric pressure and ambient temperature contains 80% of N2 and 20% of O2 without and with humidity. The X-ray flash generates relativistic (higher energy) and non-relativistic (lower energy) Compton electrons producing secondary electrons by ionizing the gas. The source terms of these secondary electrons causing the plasma formation, are taken into account in the conservation equations of electron density and electron energy density. The coupling of these two equations, give at each time step the mean secondary electron energy. Such new formalisms of source terms, allow to study the air plasma generation and relaxation without using the complex Monte Carlo method.