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

Miscellaneous · Fri Jan 01 00:00:00 EST 1993

OSTI ID:7112125

Bradley, K S

There are many phenomena which have prevented its achievement of controlled fusion. 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. Convective theory is often invoked to explain experimental observations, even when one or more of the theory's assumptions are violated. The experiments reported 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. These are the first SBS experiments 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. There are qualitative and quantitative differences in the levels of scattered light, as well as the shapes of the spectra and the evolutions of the peak scattered power. Several possible mechanisms are considered to explain these discrepancies. The theory may fail to predict the observations because it does not incorporate many of the plasma details, as well as the early-time (non-steady-state) behavior of SBS.

• Research Organization: California Univ., Davis, CA (United States)
• OSTI ID: 7112125
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
LASER-PRODUCED PLASMA
BRILLOUIN EFFECT
INERTIAL CONFINEMENT
ELECTROMAGNETIC RADIATION
EXPERIMENTAL DATA
ION ACOUSTIC WAVES
THERMONUCLEAR REACTIONS
COHERENT SCATTERING
CONFINEMENT
DATA
INFORMATION
ION WAVES
NUCLEAR REACTIONS
NUCLEOSYNTHESIS
NUMERICAL DATA
PLASMA
PLASMA CONFINEMENT
PLASMA WAVES
RADIATIONS
SCATTERING
SYNTHESIS
700340* - Plasma Waves
Oscillations
& Instabilities- (1992-)
700350 - Plasma Production
Heating
Current Drive
& Interactions- (1992-)