Investigations of Advanced CO_2 Supersonic Mixing Laser and Propulsion by Laser Absorption

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This paper deals with firstly the experimental and analytical approach to advanced scheme of CO_2 supersonic electric discharge laser, and secondly fundamental experiments on propulsion by CO_2 laser absorption. For supersonic CO_2 electric discharge laser, the cluster of supersonic and cylindrical N_2 channels for axial glow discharge are employed, and then conical screen mixing nozzles are used for supersonic mixing of CO_2. Discharge characteristics and supersonic flow properties are measured, along with small signal gain measurement. Vibrationally nonequilibrium analysis of quasi-onedimensional supersonic flow for mixing laser is also conducted, involving N_2 collisional activation by electron impact. Among the results, achievement of steady glow discharge in supersonic N_2 flow is obtained. Measured gain and power dependency on cavity flow distance, on plenum pressures, and on discharge characteristics are discussed in comparison with numerically estimated performances. The duration for maintaining the supersonic flow is about 8 sec that corresponds with our lasing duration. Secondly for the laser propulsion, fundamental experiments with 1 kW-class CW CO_2 laser are conducted. The experimental range is mainly for molecular absorption, and temperature increase is monitored. Among the results obtained, the effect of SF_6 on beam absorption in plenum is remarkable in our experimental conditions.
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