Pushing the limits of plasma length in inertial fusion laser-plasma interaction experiments

We demonstrate laser beam propagation and low backscatter in laser produced hohlraum plasmas of ignition plasma length. At intensities I < 5 x 10{sup 14} W cm{sup -2} greater than 80% of the energy in a blue (3{omega}, 351 nm) laser is transmitted through a L=5-mm long, high-temperature (T{sub e} = 2.5 keV), high-density (n{sub e} = 5 x 10{sup 20} cm{sup -3}) plasma. These experiments show that the backscatter scales exponentially with plasma length which is consistent with linear theory. The backscatter calculated by a new steady state 3D laser-plasma interaction code developed for large ignition plasmas is in good agreement with the measurements.