Investigating at-scale MagLIF preheat on the NIF

Recent MagLIF experiments at the NIF have measured the energy coupling and propagation of a ~35 kJ laser pulse in 1 cm-long gas pipe targets with hydrocarbon gas fills and pre- imposed magnetic fields <25 T. The experiments explore the effects of gas density (n e = 0.12-0.16 n c ) and magnetic field strength (0-25 T) over the relevant design space. Temporally gated, spatially resolved x-ray imagers record the profile of the heated plasma throughout the laser propagation, showing evidence for modified electron transport when the magnetic field is applied. The time required for the laser to completely burn through the target is temporally resolved with an x-ray streak camera, and laser backscatter is measured during the entire interaction, allowing for accurate assessments of minimum energy coupling to the target. These emission profiles and burnthrough times are well reproduced in 2D Hydra simulations at electron densities of 12% critical and B=0, though there are discrepancies at higher density (16% critical) and with the magnetic field. Variation of the flux limiter choice alone is insufficient to bring the model into agreement with the data, so 3D simulations including additional MHD physics processes are now underway to better reproduce the measurements. The results show up to 30 kJ energy coupled into the gas which simulations suggest is close to optimal for MagLIF designs at 47 MA drive currents [1] .