Power and efficiency of a continuous HF chemical laser

Experimental measurements of laser power output and chemical efficiency are reported for a continuous HF chemical laser. In this device, arc-heated N
2
is mixed in a plenum with SF
6
to provide F atoms. The mixture is expanded to form a supersonic jet into which H
2
is diffused. Population inversion and lasing are due to H
2
+ F → HF(υ) + H,
\upsilon \leq 3, \Delta
H = -31.7 kcal. Power levels up to 1 kW have been obtained. The efficiency of conversion of chemical energy to laser power is 16 percent at low SF
6
flow rates and approximately 10 percent at peak power. For a fixed arc power, addition of O
2
into the plenum raises peak power by about 25 percent under present operating conditions and reduces sulphur deposition on mirror surfaces. The presence of HF and DF in the plenums of DF and HF lasers, respectively, did not appear to degrade laser performance. (HF and DF levels up to 10 percent of the local F concentration were studied.) However, the presence of HF and DF in the plenums of HF and DF lasers, respectively, did degrade laser output. For given flow conditions, peak net laser power was obtained when the optical cavity axis was about 2 cm downstream of the H
2
injection station. The net output power was reduced to zero when the cavity axis location was increased to 5 cm.