Air Breakdown Initiated by Particles in an HF Laser Beam
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
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Thresholds were measured for air breakdown initiated by particles in a 3.5 microsec, 2.9 micrometers laser beam. The pulsed chemical laser at Boeing Aerospace Corporation was used for these studies. The thresholds for 50 micrometers diameter graphite, NaCl, Al2O3 particles and 10 micrometers and 30 micrometers quartz fibers were found to be factors of three to five higher than the comparable thresholds for 10.6 micrometers lasers. The material dependence for the threshold was found to differ from that for short pulse 10.6 micrometers breakdown. The radial plasma growth rate was measured and found to be approximately equal to the growth rate at 10.6 micrometers for an intensity of 3 x 10 to the 7th power Wsq.cm.
- Lasers and Masers