LIMITATION OF CO2 LASER-INDUCED GAS-BREAKDOWN

To obtain economical extraction of U-235 the molecular laser isotope s eparation (MLIS) process, 16-mu m laser beams must be generated in a p arahydrogen Raman cell with high repetition rates and sufficient inten sity. Because the intensities of the 16-mu m laser beams are dependent on the intensity of the incoming pump laser beams, the intensity of t he CO2 lasers must be kept as high as possible. The maximum intensity has, however, been found to be controlled by the onset of gas breakdow n in the Raman cell at too low a level for efficient Raman conversion. Through tests, the origin of gas breakdown in a 2-kHz-repetition-rate Raman cell is identified as particle contamination. The effect of the degree of contamination is determined and compared with experimental results. Conditions are set and modifications implemented on the Raman cell to ensure efficient Raman conversion.