Cross-beam energy transfer to a single f-20 beam: simulations of previous and upcoming experiments

Motivated by materials research applications, cross-beam energy transfer can be used to transfer energy from one or more quads of beamlets at the NIF, which have an effective $f$-number of 8, to a single $f$-20 beam. Using plasma comprised of a preheated C$_5$H$_{12}$ gasbag, a preliminary experiment at the NIF demonstrated amplification of a 750 J $f$-20 beam by a factor of 2 in both power and energy. A witness plate providing gated x-ray images was used to obtain total energies and transmitted spot intensities for the pump quad, seed beamlet, and a calibration quad. These experimental diagnostics offer the opportunity to perform quantitative comparisons with simulations. We use the laser-plasma interaction code pF3D to simulate the energy transfer process, using plasma conditions obtained from the plasma hydrodynamics code HYDRA. Our simulations of the completed single-pump quad experiment recover the measured seed amplification and transmitted spot power distributions. We also show simulation results for the upcoming two-pump quad experiment.