Line VISAR measurements of energy deposition for next generation MagLIF laser preheat at NIF*

Gas-pipe experiments on the NIF have investigated MagLIF laser preheat at scales relevant to next-generation pulsed-power facilities.  Experiments have been done into magnetized (up to 28 Tesla), room temperature, hydrocarbon and unmagnetized D2 gases of densities that span 1.6 mg/cc to 4.8 mg/cc (5% to 16% critical electron density).  Up to 30 kJ of energy from one quad has been delivered into an oval spot of 1580 micron mean diameter over a time of about 11 ns with a power of 2 TW and an intensity of 2 x 10¹⁴ W/cm².  A critical measurement in these experiments is the laser energy deposited though inverse Bremsstrahlung absorption in the gas. In this talk we describe line VISAR measurements taken in unmagnetized hydrocarbon-gas experiments. We show how the shock timing and velocity measured by line VISAR can be related to energy deposition over the 1 mm extent of the diagnostic view.