Brillouin Backscatter Dependence Upon Pulse Amplitudes, Timing, Target Material and Geometry.
NAVAL RESEARCH LAB WASHINGTON DC
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The stimulated Brillouin backscatter instability plays an important role in the laser-plasma interaction for short is less than 1 nsec, high-irradiance is greater than 10 to the 13 power Wsq cm Nd-laser pulses. Laser light is observed to be directly backscattered and the total absorption fraction reduced by this mechanism operating in the underdense region of plasma. Long underdense plasma scale lengths, which are conducive to large simulated backscatter, are set up, for example, in a plasma preformed by a small prepulse, longer incident pulses and larger plasmas, and by temporally structured pulses designed for laser fusion. The density gradient present when the high-intensity pulse strikes the target and hence the degree of backscatter is expected to be a function of several variables. Here we show the variation of backscatter with main pulse-prepulse timing and amplitudes, target material and geometry.
- Lasers and Masers
- Plasma Physics and Magnetohydrodynamics