An experimental investigation of stimulated Brillouin scattering in laser-produced plasmas relevant to inertial confinement fusion

Thesis/Dissertation · Thu Feb 11 00:00:00 EST 1993

DOI:https://doi.org/10.2172/10176900· OSTI ID:10176900

Bradley, Keith Stanley ^[1]

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1. Univ. of California, Davis, CA (United States)

Despite the apparent simplicity of controlled fusion, there are many phenomena which have prevented its achievement. One phenomenon is laser-plasma instabilities. An investigation of one such instability, stimulated Brillouin scattering (SBS), is reported here. SBS is a parametric process whereby an electromagnetic wave (the parent wave) decays into another electromagnetic wave and an ion acoustic wave (the daughter waves). SBS impedes controlled fusion since it can scatter much or all of the incident laser light, resulting in poor drive symmetry and inefficient laser-plasma coupling. It is widely believed that SBS becomes convectively unstable--that is, it grows as it traverses the plasma. Though it has yet to be definitively tested, convective theory is often invoked to explain experimental observations, even when one or more of the theory`s assumptions are violated. In contrast, the experiments reported here not only obeyed the assumptions of the theory, but were also conducted in plasmas with peak densities well below quarter-critical density. This prevented other competing or coexisting phenomena from occurring, thereby providing clearly interpretable results. These are the first SBS experiments that were designed to be both a clear test of linear convective theory and pertinent to controlled fusion research. A crucial part of this series of experiments was the development of a new instrument, the Multiple Angle Time Resolving Spectrometer (MATRS). MATRS has the unique capability of both spectrally and temporally resolving absolute levels of scattered light at many angles simultaneously, and is the first of its kind used in laser-plasma experiments. A detailed comparison of the theoretical predictions and the experimental observations is made.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 10176900
• Report Number(s): UCRL-LR-113062; ON: DE93018067; TRN: 93:018913
• Resource Relation: Other Information: DN: Thesis submitted to University of California, Davis, CA (US); TH: Thesis (Ph.D.); PBD: 11 Feb 1993
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
LASER-PRODUCED PLASMA
PARAMETRIC INSTABILITIES
INERTIAL CONFINEMENT
NOVA FACILITY
LASER FUSION REACTORS
EXPERIMENTAL DATA
BRILLOUIN EFFECT
ELECTROMAGNETIC RADIATION
ION ACOUSTIC WAVES
PLASMA DENSITY
COMPARATIVE EVALUATIONS
SPECTROMETERS
COMPTON EFFECT
LASER TARGETS
VISIBLE SPECTRA
PLASMA DIAGNOSTICS
INHOMOGENEOUS PLASMA
700340
700411
PLASMA WAVES, OSCILLATIONS, AND INSTABILITIES
INERTIAL CONFINEMENT DEVICES