Experimental determination of the parameters of a laser jet and verification of ionization equilibrium

Spectroscopic methods were used to make an experimental investigation of the electron and brightness temperatures, the atomic concentrations, and the electron density in an optical breakdown plasma formed by the interaction of double laser radiation pulses (of 10.6-μm wavelength), each of 2.5-μs duration, with a Dural target in air at atmospheric pressure. Independent measurements of the plasma parameters made it possible to compare the experimentally measured values of the electron density with those calculated on the basis of the Saha equation. The fact that the calculated value of the electron density exceeded the measured value (by a factor of more than 5) indicated breakdown of an ionization equilibrium in the optical breakdown plasma even after the end of the interaction between the laser radiation and the target.