Gain and energy measurements on an HF/DF electrically pulsed chemical laser
1.Electroplating of the 1/2‐in. ‐diam brass cathode with nickel apparently rendered the bar less susceptible to gradual pitting by the discharge. A pit in the cathode surface dramatically enhanced the probability of arcing to that point.
2.Four parallel 30‐kV 500‐pF capacitors (Sprague 715‐Z) comprised the 2000‐pF capacitance. Reliable switching of the EG&G GP‐14B spark gap could not be accomplished below 14 kV.
3.At 28 kV the current pulse was characterized by a peak current of 250 A, as measured with a Pearson Model 410 current transformer. A 25% reduction in the pulse width was obtained with a low‐inductance (1 nH) Maxwell capacitor. A Plastic Capacitors 60‐kV 2000‐pF capacitor produced a much longer current pulse (̃1 μsec) and a much greater frequency of arcing.
4.C. R. Jones, L. J. Gerenser, and R. G. Adams (unpublished).
5.S. Marcus and R. J. Carbone, IEEE J. Quantum Electron. QE‐7, 493 (1971).
6.J. Goldhar, R. M. Osgood, Jr., and A. Javan, Appl. Phys. Lett. 18, 167 (1971).
7.Four l/2‐in.‐diam apertures were centered on the optical axis and equally spaced along the gain medium. Cut from sandblasted acrylic material to avoid specular reflection, the stops somewhat increased the threshold for parasitic oscillations.
8.In Ref. 6 the authors attributed strong optical signals from a similar chemical HF/DF laser (with no output coupler) to superradiance because there were apparently no surfaces external to the tube which produced regenerative feedback. It is probable that their signals were also parasitic oscillations supported by reflections from internal surfaces of the laser tube.
9.Operation with no output coupler yielded a 1.2‐mJ output, which is reasonable since the gain under these conditions is far above parasitic oscillation threshold. Understandably, the beam quality measured under conditions of heavy parasitics was of very poor quality. Also, it was found to be almost impossible to operate single line with an intracavity grating because of uncontrollable oscillation of the HF line.
10.S. N. Suchard, R. L. Kerber, G. Emanuel, and J. S. Whittier, J. Chem. Phys. 57, 5065 (1972).
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