Thomson scattering from a shock front

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 m 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 20m-thick beryllium drive disk, 0.3m-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 m light at 5 1014 W/cm2 for 1 ns starting at to, driving a strong shock through argon gas at o=1 mg/cc. 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. DOI: 10.1063/1.2220069