National Ignition Facility preamplifier update

Summary form only given. The National Ignition Facility (NIF) preamplifier is an intermediate stage of amplification between the fiber oscillator and the main Nd:glass slab multipass amplifiers. The preamplifier module (PAM) will amplify the light from approximately 1 nJ up to a maximum injection energy of 17 J before the beam is split into four beamlines that provide a final 1.053-/spl mu/m energy of 20 kJ/beamline. In this high-gain regime the PAM is a two-stage amplifier with a regenerative amplifier in the first stage producing 15-20 mJ at 1 Hz. This energy is then amplified again to the higher energies when needed through a four-pass 5-cm Nd:glass rod amplifier. The PAM is a line replaceable unit made to be rugged enough to operate for an extended period of time without maintenance. During this extended period of semi-autonomous, computer controlled operation the PAM must be capable of amplifying a variety of temporal and spatial pulse shapes while always meeting a stringent set of temporal, spatial, wavefront, and pointing requirements.