Thomson scattering from a shock front

Abstract

We have obtained a Thomson scattering spectrum in the collective regime by scattering a probe beam from a shock front, in an experiment conducted at the Omega laser at the Laboratory for Laser Energetics. The probe beam was created by frequency converting a beamline at Omega to a 2 ns pulse of 0.263 μm light, focused with a dedicated optical focusing system. The diagnostic system included collecting optics, spectrometer, and streak camera, with a scattering angle of 101°. The target included a primary shock tube, a 20-μm -thick beryllium drive disk, 0.3-μm -thick polyimide windows mounted on a secondary tube, and a gas fill tube. Detected acoustic waves propagated parallel to the target axis. Ten laser beams irradiated the beryllium disk with 0.351 μm light at 5× 1014 W cm2 for 1 ns starting at to, driving a strong shock through argon gas at ρ o =1 mgcc. The 200 J probe beam fired at t=19 ns for 2 ns, and at t=20.1 ns a 0.3 ns signal was detected. We attribute this signal to scattering from the shocked argon, before the density increased above critical due to radiative collapse. © 2006 American Institute of Physics.