Modelizacao cinetica de plasmas de helio mantidos por campos de alta frequencia

Abstract

Helium is a major constituent of various gas discharge mixtures used today in many applications such as plasma lasers (CO_2:#NU#_2:#ETA#e; #ETA#e:#NU#e and #ETA#e:Cd). For this reason, the kinetic study of pure helium plasmas is a subject of wide interest as it constitutes an intermediate step towards a deeper understanding of gas discharges in such mixtures. Gas discharges in pure helium are also interesting by themselves from a theoretical view-point. Indeed, fundamental knowledge is still required on electron cross sections and rate coefficients for diffusion, recombination and atomic collisions, in pure helium, under the action of applied HF fields. This work is concerned with a detailed analysis of the plasma kinetics in pure helium by solving the electron Boltzmann equation and the transport equations, using several different approximations, according to the specific situation under investigation. The models here developed constitute power full theoretical methods for the self-consistent calculation of a number of space and time dependent physical quantities necessary for a complete understanding of the plasma medium, such as the populations of the principal species as well as their creation/loss frequencies, the electron energy distribution functions, the energy averaged quantities (rate coefficients, transport parameters, etc), and the consistent fields involved in the transport of the charge particles to the wallAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga