Testing the Effects of Focal-Spot Zooming on Cross-Beam Energy Transfer Mitigation Using Laser-Direct-Drive Implosions at the National Ignition Facility*

As part of a laser-direct-drive (LDD) IFE (inertial fusion energy) platform, LLE is investigating using focal-spot zooming (FSZ) to enhance laser–energy coupling; providing an efficient use of laser energy in future IFE ignition designs. In the near term, rudimentary FSZ at the National Ignition Facility (NIF) offers the capability to develop a platform to study the concept and benefits of FSZ in current LDD experiments. Of particular interest is the use of FSZ to offset the deleterious effects of cross-beam energy transfer (CBET). Results from 2D draco simulations will be presented detailing an experimental platform to illustrate the effect that FSZ has in offsetting poor laser coupling caused by CBET. In addition, we examine the role of CBET in LANL bosque target designs and the effect that FSZ had in their recent NIF experiments.