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Time-Dependent Oscillations in a cw HF Chemical Laser Unstable Resonator
AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH
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The multi-line performance of a cw HF chemical laser was measured as a function of the SF6 and H2 flow rates, pressure and resonator type. The Blase II and MNORO3 cw chemical laser computer codes gave reasonable agreement with the experimental data as the flow rates and pressure were varied. Total power and beam diameter increased as the pressure decreased. The data indicate the occurrence of a near resonant energy transfer from v2, J3, 4 to v2, J14 with a subsequent rotational cascade to v2, J11. The amplitude, frequency and Fresnel number dependence of the time-dependent oscillations which were predicted to occur on lines whose saturated gain does not fill the unstable resonator were measured. The time-dependent oscillations had a period of abour 40 ns independent of flow rates, do not occur for Fresnel numbers less than 1.5 and their amplitudes increased as the fraction of the resonator filled by the saturated gain of the oscillating line decreased.
APPROVED FOR PUBLIC RELEASE