燃焼駆動式CO₂ガスダイナミックレーザーの性能

(III)レーザー出力特性

抄録

Laser output power characteristics of the combustion-driven CO₂ Gasdynamic Laser (CO₂GDL) are presented. Laser extraction is carried out with supersonic nozzle of circular-circular (CC) and shock free (SF), which has common area-ratio (A/A*=20) and various expansion length (CC nozzle with expansion length of 30mm and SF nozzle of 45, 33, 20mm). In laser output power measurements, maximum power of 24.5W is obtained at CC 20 nazzle of expansion length of 30mm, which has maximum small-signal gain of 0.5m^-1. However, at SF nozzle which has small-signal gain of 0.2-0.3 m^-1, laser output power can not be obtained. Investigation of the laser excitation condition suggests that the system requires the threshold value for small-signal gain over 0.23m^-1. It is concluded that, with these results a feasible laser excitation system by the CO₂GDL with CC nozzle has been established. Increase of small-signal gain, extension of cavity width and selection of most suitable laser light resonator will provide a radiative heating simulator for thermal protection research.