On the problem of creation of high-energy far infrared H2O gasdynamic laser -: Experimental and theoretical studies

Theoretical and experimental analysis of a possibility of creation of high-energy gasdynamic laser generating infrared radiation with wavelength lambda=27.971 mum on the vibration-rotation transition 001(633)-->020(5(50)) of H2O molecule is presented. It was shown that at expansion of preheated water vapour in a wedge-shaped supersonic nozzle with 30degrees opening angle and critical section height h(*)less than or equal to1 mm the nonequilibriurn population of vibrational levels 001 and 020 of H2O molecules is realised for the pressures P-0=0.2-0.5 MPa and the temperatures T-0= 1930-2580 K at the nozzle inlet. The numerical analysis has demonstrated that for a plate profiled nozzle whose supersonic section is designed to provide uninterrupted flow at initial parameters T-0=2500 K, P-0=0.3 MPa, h(*)=0.1 mm and nozzle expansion ratio epsilon=20 the amplification coefficient behind the nozzle may achieve 1 m(-1). In this case the specific radiation energy may be of about 20 J/g. The principal feature of H2O-gasdynamic laser is necessity to use the nozzle with rapid expansion and small values of parameter P(0)h(*). The latter should be considerably less (in a factor of 50-100) than for traditional CO2-gasdynamic lasers.