Electrostatic Cooling of Laser Mirrors and Windows.

Investigations have been conducted to determine the mechanism of electrostatic cooling and to optimize its application for laser mirrors and windows. Electrostatic cooling in air is found to be essentially an ionic drag phenomenon in which the convective heat transfer coefficient is proportional to the fourth root of corona current. Results on samples of ZnSe, aluminum, and CerVit, ranging from 1.5 to 4-in. diameter, indicate that convective cooling by electric probes in air is generally 10 to 15 times the natural convection cooling rate. This cooling rate may be increased by another factor of 2 if a polar gas is used instead of air. A guide for the estimation of electrostatic cooling for a prescribed system is given by a theoretically-formulated approximate equation which relates heat transfer coefficients to corona current, sample size, and gas parameters. Design recommendations for applications to laser mirrors and windows are included, and several optimization techniques are suggested. Author