Performance of the beamlet laser, a testbed for the National Ignition Facility

We present initial performance studies for Beamlet, a single-beam prototype for megajoule-class neodymium-glass laser fusion drivers using a multipass main amplifier, adaptive optics, and efficient, high-fluence conversion to the third harmonic. The Beamlet final amplifier uses Brewsters-angle glass slabs with a square 39 {times} 39 cm{sup 2} aperture and a full-aperture plasma-electrode Pockels cell switch. The laser has been tested at the fundamental wavelength over a range of pulselengths from 1-10 ns up to energies of 5.8 kJ at 10 ns and 17.3 kJ at 10 ns at a beam area of 35 {times} 35 cm{sup 2}. A 39-actuator deformable mirror system corrects the beam to a Strehl ratio of 0.4