Cyclotron resonant gas breakdown with a 1.22‐mm13CH3F laser
作者:
M. P. Hacker,
B. Lax,
R. N. Metz,
R. J. Temkin,
期刊:
Journal of Applied Physics
(AIP Available online 1979)
卷期:
Volume 50,
issue 1
页码: 121-126
ISSN:0021-8979
年代: 1979
DOI:10.1063/1.325694
出版商: AIP
数据来源: AIP
摘要:
Cyclotron‐resonant laser‐induced gas breakdown has been studied for the first time in the transverse geometry, using 1.222‐mm13CH3F laser radiation propagating perpendicular to the magnetic field axis. The line shape of absorbed laser radiation versus magnetic field near electron cyclotron resonance (87.75 kG) indicates a strong dependence of the line shape on the focused laser intensity. This dependence is not predicted by the standard equilibrium theory of high‐frequency gas breakdown in a magnetic field. We have developed an analytic theory to explain the observed line shapes. The theory takes into account the laser propagation characteristics, in particular that there is nonuniform ionization due to strong resonant absorption of the laser radiation in a length comparable to or shorter than that of the laser focal volume. The transverse geometry simplifies the theoretical analysis because the observed line shapes are not significantly affected by Doppler broadening. Extensive data have been obtained on the fraction of laser pulse energy absorbed in the gas breakdown volume as a function of magnetic field, helium gas pressure, and incident laser pulse energy. Good quantitative agreement is obtained between the observed laser pulse absorption line shapes and the nonuniform ionization theory.
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