Self-focusing effects in large, high power laser amplifiers become manifest as small-scale beam instabilities and as large-scale phase aberrations. Spatial filtering has been shown to control instabilities; spatial filters constitute appropriate lens pair elements for image relaying as well. In this paper, image relaying is presented as a technique for preserving the transverse intensity profile of a high power beam as it propagates long distances through nonlinear elements. As a consequence, amplifier apertures can be filled more effectively, leading to a doubling of fixed-aperture system performance. A rationale for optimal selection of spatial filter bandpass is also presented. This selection, as might be expected, depends upon details of the beam's spatial structure as it enters any filter. A geometrical optics approach is used throughout; nevertheless, derived results remain valid when diffraction is included.

The goals of the recently activated Nova laser facility are to address critical issues for evaluating the feasibility of inertial confinement fusion, to implode DT to densities exceeding 200 g/cm3 and pressures greater than 1011 atm, and to perform a wide range of high energy density plasma physics experiments in the areas of XUV/x-ray lasers, hydrodynamics, and radiation generation and transport. An extremely flexible and sophisticated facility is required to successfully perform such a variety of tasks. The ten-arm Nova laser is capable of irradiating complex targets with laser wavelengths of 0.53 and 0.35 μm and pulse widths that range from 0.09 to >5 ns, and peak powers greater than several terrawatts per beam line. A sophisticated, variable impedance, transmission line driven Pockels cell allows for complex temporal shaping of the laser pulse. Synchronized oscillators allow for different pulses to be propagated down the beam lines for experiments that require long-pulse or short-pulse x-ray backlighting. The output of the laser can be directed into two independent target areas: a 4.4-m-diam vacuum vessel for experiments which require 10 beams, and a 1.8-m-diam chamber for two Nova arms. The facility has been designed to allow nearly simultaneous, independent experiments to be conducted in both target areas. A number of sophisticated optical, XUV, x-ray, and particle diagnostics measure target performance. An optical fiducial system allows cross correlation of all of the diagnostic systems to better than 50 ps. An overview of the facility, diagnostics, and data-acquisition system will be discussed.

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