Time-gated measurements of fusion-class laser beam profiles

The National Ignition Facility (NIF) laser produces 192 pulsed beams with transverse dimensions ∼40 cm × 40 cm and a diversity of temporal shapes with typical durations ranging from 1 to 30 ns and a total energy on target up to 2.1 MJ in the UV.1 Standard diagnostics include near-field cameras that record the spatial dependence of the time-integrated pulse fluence, as well as sensors that record the spatially integrated pulse power versus time. While these diagnostics are indispensable, beamlines and the pulses they transport may be better characterized with a diagnostic that reveals more of the spatio-temporal pulse structure, i.e., the local irradiance, especially in the presence of nonlinear optical effects. Recently, the time-resolving capability of the Icarus camera has been leveraged in the Precision Diagnostic System (PDS) at the NIF. The Icarus is a gated CMOS sensor designed to capture X-ray images in various experimental settings.2, 3 However, its sensitivity in the near-IR is sufficient for capturing time-gated images of NIF beams, thus opening the door to better characterization than is possible with standard space- and/or time-integrated diagnostics. In this work, we present the first time-gated beam profiles measured in PDS at the NIF during high-energy and high-peak-power experiments, and discuss their implications in terms of past, present, and future laser performance.