Demonstration of beam propagation through hohlraum plasmas at NIF like temperatures

We have measured the propagation and backscatter of a 2$\omega$ (527 nm) high intensity ($\sim$5x10$^{14}$ W/cm$^2$) interaction beam through large-scale length plasmas at NIF like temperatures of up to 4 keV. The plasma is created by heating 2 mm x 1.6 mm diam. hohlraum targets with 37 defocused heater beams at 3$\omega$, delivering a total energy of 16 kJ in a 1 ns square pulse. A dedicated 2$\omega$ interaction beam probes the preformed plasma along the hohlraum axis. We have measured beam propagation and backscatter both in gas-filled and in foam-filled targets at 2$\omega$ NIF design densities around n$_e$/n$_c$=5\% (at 3$\omega$). We observe a beam transmission as high as 80\% with negligible SRS reflectivity and modest levels of SBS. Both 2$\omega$ and 3$\omega$ SBS spectra and Thomson scattering measurements are consistent with a plasma temperature above 3.5 keV, which is a factor of two higher than the temperatures in gasbag-plasmas that were studied previously.