Full-aperture backscatter measurements on the National Ignition Facility

The National Ignition Facility’s full-aperture backscatter station (FABS) is described. The FABS uses five independent diagnostics on each of the four laser beams in the initial National Ignition Facility quad to measure the energy, power, spectrum, and near-field amplitude modulations of the stimulated Brillouin and stimulated Raman backscattered light. In initial tests CO2 and C5H12 gas-filled targets were used to create various laser–plasma interaction conditions which have shown the capability of producing ignition size laser plasmas with reflectivites on the order of 10%. Results are presented for tests in which 16 kJ on target produced between 0.3 and 2.5 kJ of backscattered light.