Vacuum laser-initiated plasma shutters for retropulse isolation in Antares

Abstract

We have demonstrated that sintered LiF spatial filters may be used in a 10/sup -6/-torr vacuum environment as laser-initiated plasma shutters for retropulse isolation in the Antares high-energy laser fusion system. In our experiments, a 1.1-ns pulsed CO/sub 2/ laser, at a 10-..mu..m wavelength and an energy of up to 3.0 J, was used for plasma initiation; a chopped probe laser tuned to a 9l6-..mu..m wavelength was used in determining the blocking time of the plasma. We measured the 10.6- and 9.6-..mu..m beam transmissions as a function of fluence on the aperture edge. For an 800-..mu..m-diam aperture and a 1.2-mm-diam Gaussian beam determined at the 1/e/sup 2/ intensity points, we observed blocking times in excess of 1.0 ..mu..s.