CHAPTER 3 - Gas Discharge Processes

Abstract

This chapter focuses on gas discharge processes. The possibility that a gas discharge could be used to give a nonequilibrium population distribution necessary to support laser oscillation appears to have been first recognized by Fabrikant as early as 1939. However, it was not until 1959 and 1960 that specific proposals were made for laser systems utilizing the mechanisms operating in a gas discharge. There have been a number of excellent analyses of the glow discharge, for example, those of von Engel, Francis, Parker, and Brown. The negative glow is a beam-maintained, recombination-dominated plasma region. Though it is maintained by high-energy electrons that have been emitted by the cathode and accelerated across the high-field region of the cathode dark space, it is dominated by recombination mechanisms involving secondary, low-energy electrons and thermal-energy positive ions that have been produced by the high-energy electrons in ionizing collisions in ion-pair production. Near the boundary between the cathode dark space and the negative glow, the electric field is weak, and only the fast electrons that have not lost energy in inelastic collisions will be able to ionize.