ARC Stray Light Mitigation

Abstract

The National Ignition Facility (NIF) is the world’s largest and most energetic laser system, located at Lawrence Livermore National Laboratory (LLNL). It is designed to study inertial confinement fusion and to conduct numerous other experiments. NIF has 192 laser beams that are directed at a small targets located at the center of a 5-m radius spherical vacuum chamber. Currently, four of these 192 beamlines (“one quad”) are undergoing modification to achieve peak power exceeding 10 15 Watts. Though the beams will have about the same energy as other NIF beams, the pulses will be compressed in time to achieve such high peak powers. This new petawatt-class laser, called Advanced Radiographic Capability (ARC), will be the world’s highest-energy, ultra-short-pulse laser and will be used to produce x-rays for backlighting NIF experiments. The 192 laser beams travel about 1.5 km in optical path length down the NIF beamline to the target chamber. It is only in the last few dozen meters, just before entering the target chamber, where the ARC quad is picked-off from the main beamline to enter a compressor vessel to decrease the pulse length and then the parabola vessel to point and focus the light onto the backlighter target.