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.