Investigating the energy balance in MagLIF preheat experiments

The Magnetized Liner Inertial Fusion (MagLIF) concept requires that multi-kJ of laser energy be coupled to the D₂ fuel during the “preheat” stage. How efficiently laser energy is coupled into the gas is impacted by various loss mechanisms such as laser-plasma instabilities (LPI) and the need to penetrate through a laser entrance hole (LEH) foil. Recent experiments have employed cryogenic cooling enabling thinner, larger diameter LEH foils and larger spot-size laser beams. This has dramatically improved the measured coupling efficiency to ~88% from ~64% in the best performing warm configurations enabling >2 kJ to be coupled for the first time in integrated experiments. In this presentation we will discuss how the coupling efficiency is assessed, the various factors that impact the coupling efficiency and the implications.