Photoionization of the upper excited states and perturbation of the positive column of a glow discharge by CO2 laser radiation

The effects of 10.6-micron 250-nsec-pulsed 1-1000-kW/sq cm radiation from a CO2 laser on the plasma in the positive column of a stationary He glow discharge with length 19.5 cm, radius 1 mm, pressure about 100 Pa, E/p 7.5-30 V/m Pa, and current 4-100 mA (studied experimentally by Kirillin and Khodakov, 1983) are investigated theoretically. Both the heating of the electrons in the laser radiation field and the photoionization of the upper excited states are taken into account, and the results are presented in graphs. It is found that the photoionization effect is dominant, so that little accuracy is lost by ignoring the heating effect when calculating the current sensitivity of the positive column. The implications of these results for the use of gas discharges as IR detectors are indicated.