Shiva: a 30 terawatt glass laser for fusion research

The Shiva laser system employs a single actively mode-locked Nd:YAG oscillator operating at 1.06 μ to drive 20 glass amplifier chains. Figure 1 is a schematic of a single chain. As shown each chain contains, in order 2.5-cm and 5-cm rod amplifiers followed by 10-cm, 15-cm and 20-cm disk amplifiers. Small signal gains for these amplifiers are 40, 15, 3.8, 2.6 and 1.9 respectively. Pockels' cell and Faraday rotator stages are used to suppress parasitic oscillations and protect the chain from target reflections. Spatial filters placed at regular intervals along the chain dramatically increase the focusability of the beam by removing high frequency spatial modulation and by relaying the image of the flat-topped beam profile from one amplifier stage to the next. The image relay properties of the filters, by ameliorating diffractive effects, allow the aperture of the amplifiers to be effectively filled by the beam. The components of the Shiva laser are mounted on two separate support structures constructed of square steel tubing. A model is shown of these structures as they appear in the laser and target bay of the High Energy Laser Facility