A first set of shock propagation, laser-plasma interaction, hohlraum energetics and hydrodynamic experiments have been performed using the first 4 beams of the National Ignition Facility (NIF), in support of indirect drive Inertial Confinement Fusion (ICF) and High Energy Density Physics.

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. (C) 2004 American Institute of Physics.

The full aperture backscatter system provides a measure of the spectral power, and integrated energy scattered by stimulated Brillouin (348–354 nm) and Raman (400–800 nm) scattering into the final focusing lens of the first four beams of the NIF laser. The system was designed to provide measurements at the highest expected fluences with: (1) spectral and temporal resolution, (2) beam aperture averaging, and (3) near-field imaging. This is accomplished with a strongly attenuating diffusive fiber coupler and streaked spectrometer and separate calibrated time integrated spectrometers, and imaging cameras. A new technique determines the wavelength dependent sensitivity of the complete system with a calibrated Xe lamp. Data from the calibration system are combined with scattering data from targets to produce the calibrated power and energy measurements that show significant corrections due to the broad band calibrations.

The first experiments on the National Ignition Facility (NIF) have employed the first four beams to measure propagation and laser backscattering losses in large ignition-size plasmas. Gas-filled targets between 2 and 7 mm length have been heated from one side by overlapping the focal spots of the four beams from one quad operated at 351 nm (3omega) with a total intensity of 2 x 10(15) W cm(-2). The targets were filled with 1 atm Of CO2 producing up to 7 mm long homogeneously heated plasmas with densities of n(e) = 6 x 10(20) cm(-3) and temperatures of T-e = 2 keV. The high energy in an NIF quad of beams of 16kJ, illuminating the target from one direction, creates unique conditions for the study of laser-plasma interactions at scale lengths not previously accessible. The propagation through the large-scale plasma was measured with a gated x-ray imager that was filtered for 3.5 keV x-rays. These data indicate that the beams interact with the full length of this ignition-scale plasma during the last similar to1 ns of the experiment. During that time, the full aperture measurements of the stimulated Brillouin scattering and stimulated Raman scattering show scattering into the four focusing lenses of 3% for the smallest length (similar to2 mm), increasing to 10-12% for similar to7 mm. These results demonstrate the NIF experimental capabilities and further provide a benchmark for three-dimensional modelling of the laser-plasma interactions at ignition-size scale lengths.