Method of Measuring Electron Density in Pulse Metal Vapor Lasers Using Microwave Technique

Abstract

A method of measuring the electron density kinetics in the plasma of pulse-periodic metal vapor and metal compound vapor lasers using microwave technique within the wavelength region of 78–142 GHz is realized. The method is based on the dependence of the absorption efficiency of a probe microwave radiation on the frequency of electron collisions and also on the dependence of the “cut-off” or the critical density on the frequency of the probe radiation. In a quasioptical translucence scheme the plasma of a copper bromide vapor laser is studied within an interpulse time interval in a gas-discharge tube of 20 mm in inner diameter and with a 300 mm long active heated region excited by a capacitor discharge with a pulse repetition rate of 10 kHz. It is shown that under operational conditions typical for metal vapor lasers the absorption of the probe radiation within the interpulse intervals is totally determined by Coulomb electron–ion collisions. This allows one to measure both the density kinetics and the electron temperature. Probable measurement errors are analyzed and it is shown that they result in a systematic error for the absolute value of the electron density but have a slight influence on the density kinetics.