Formation of runaway electron distribution function during gas breakdown in high electric fields

摘要

This paper presents a simple kinetic equation for the analysis of the runaway electron distributionfunction (EDF) during a dense gas breakdown in high electric fields. Characteristic scales (inenergy and space) are obtained from a formal solution of the kinetic equation, and an analyticalsolution for the EDF is derived in the plasma region where the EDF does not depend on spatialcoordinates and depends on electron velocity and time via a combination ξ= t-v/a , where ais the net electron acceleration. Kinetic analysis of the cathode sheath dynamics confirms theabsence of the cathode directed ionisation wave in the absence of electron emission from the cathode.