Laser Beam Deflection Induced by Transverse Plasma Flow

ICF quarterly report October-December 1998 volume 8, number 1

“…SBS occurs when the beam reaches the high-Z Au plasma of the hohlraum wall and is scattered back, but will not retrace the incoming path, resulting in a spatial shift of the SBS signal as observed with the NBI detector. This interpretation is consistent with so-called spot motion experiments 18,33 and with calculations 34 for unsmoothed laser beams. The experiments described by Delamater et al 18 and Kauffman et al 33 show a deflection of laser beams toward the LEHs, which was greatly reduced when beam-smoothing techniques were applied.…”

“…The experiments described by Delamater et al 18 and Kauffman et al 33 show a deflection of laser beams toward the LEHs, which was greatly reduced when beam-smoothing techniques were applied. The calculations by Hinkel et al 34 show a deflection of unsmoothed laser beams by about 6¡ for parameters similar to those in this study. Those results are in reasonable agreement with the observation in Figure 5.…”

Propagation of realistic beams in underdense plasma

“…In both cases, the density response near M = 1 is almost triple the response at~= O. This demonstrates that the process of filamentation [14] is enhanced by near-sonic transverse flow.…”

Inertial Confinement Fusion quarterly report, January-March 1998, volume 8, number 2

“…The parameters of the calculations were a 3ω beam with intensities of I = 3 × 10 15 W/cm 2 in a 3-keV plasma with 0.1 n e /n cr . Scaling this result to our conditions via 32 (Iλ i 2 )/T e × n e / n cr gives a deflection angle of φ ≤ 1°. Refraction can be estimated with φ (rad) ≅ 0.5 × (∆n L)/(n cr ∆y) where L is the path length of the laser beam through a plasma region which shows density variation ∆n across the beam waist ∆y.…”