Shock timing technique for the National Ignition Facility

Among the final shots at the Nova laser [Campbell , Rev. Sci. Instrum. 57, 2101 (1986)] was a series testing the VISAR (velocity interferometry system for any reflector) technique that will be the primary diagnostic for timin g the shocks in a NIF (National Ignition Facility) ignition capsule. At Nov a, the VISAR technique worked over the range of shock strengths and with th e precision required for the NIF shock timing job-shock velocities in liqui d D-2 from 12 to 65 mum/ns with better than 2% accuracy. VISAR images showe d stronger shocks overtaking weaker ones, which is the basis of the plan fo r setting the pulse shape for the NIF ignition campaign. The technique is s o precise that VISAR measurements may also play a role in certifying beam-t o-beam and shot-to-shot repeatability of NIF laser pulses. (C) 2001 America n Institute of Physics.