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Propagation velocities of laser-produced plasmas from copper wire targets and water dropletsExperiments were performed to determine the plasma propagation velocities resulting from KrF laser irradiation of copper wire target (75 microns diameter) and water droplets (75 microns diameter) at irradiance levels ranging from 25 to 150 GW/sq cm. Plasma propagation velocities were measured using a streak camera system oriented orthogonally to the high-energy laser propagation axis. Plasma velocities were studied as a function of position in the focused beam. Results show that both the shape of the plasma formation and material removal from the copper wire are different and depend on whether the targets are focused or slightly defocused (approximately = 0.5 mm movement in the beam axis). Plasma formation and its position relative to the target is an important factor in determining the practical focal point during high-energy laser interaction with materials. At irradiance of 100 GW/sq cm, the air plasma has two weak-velocity components which propagate toward and away from the incident laser while a strong-velocity component propagates away from the laser beam as a detonation wave. Comparison of the measured breakdown velocities (in the range of 2.22-2.27 x 10(exp 5) m/s) for air and the value calculated by the nonlinear breakdown wave theory at irradiance of 100 GW/sq cm showed a quantitative agreement within approximately 50% while the linear theory and Gaussian pulse theory failed. The detonation wave velocities of plasma generated from water droplets and copper wire targets for different focused cases were measured and analyzed theoretically. The propagation velocities of laser-induced plasma liquid droplets obtained by previous research are compared with current work.
Document ID
19950042795
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Song, Kyo-Dong (NASA Langley Research Center Hampton, VA, United States)
Alexander, Dennis R. (Univ. of Nebraska-Lincoln, Lincoln, NE United States)
Date Acquired
August 16, 2013
Publication Date
September 15, 1994
Publication Information
Publication: Journal of Applied Physics
Volume: 76
Issue: 6
ISSN: 0021-8979
Subject Category
SOLID-STATE PHYSICS
Funding Number(s)
CONTRACT_GRANT: DAAL03-87-K-0138
Distribution Limits
Public
Copyright
Other