Monitoring preheat performance in Magnetized Liner Inertial Fusion experiments with stimulated Raman and Brillouin backscatter measurements

The Magnetized Liner Inertial Fusion (MagLIF) platform requires efficient coupling of laser energy to the underdense D₂ fuel to produce significant fusion yield. Although laser-plasma instabilities typically constitute undesirable loss mechanisms of laser energy, their signatures help monitor the performance of laser preheat in MagLIF experiments. We present time-resolved spectral measurements of stimulated Raman and Brillouin backscatter from preheat experiments conducted on both the Z Machine and the PECOS target chamber at SNL. The measurements exhibit time-dependent signatures of the density and temperature of the laser entrance window and heated plasma channel produced in the gas by the Z Beamlet laser. The measurements demonstrate significant differences in the laser-plasma interactions when changing the laser pulse shape and beam profile.