Dense cryogenic fuel layers for high performance magnetized liner inertial fusion

Magnetized Liner Inertial Fusion (MagLIF) implosions driven by the Z machine produce greater than 10¹³ DD fusion reactions [M.R. Gomez et al. Phys. Rev. Lett. 113, 155003 (2014)]. Simulations indicate that much higher yields should be possible with increased drive current, fuel density, preheat energy, and dense cryogenic fuel layers [S.A. Slutz et al. Phys. Plasmas 23, 022702 (2016)]. Dense cryogenic fuel layers (deuterium or deuterium/tritium) on the inner surface of liners should also reduce mix enhanced radiation losses by separating the fuel from typical liner materials such as beryllium. However, at temperatures low enough to form hydrogen ice the vapor density is only 0.3 mg/cc, which is not high enough for MagLIF operation. We present two solutions to this problem. First, a fuel wetted low density plastic foam can be used to form a layer on the inside of the liner. The desired vapor density can be obtained by controlling the temperature. This does however introduce carbon into the layer, which will enhance radiation losses. Second, we show that low temperature gaseous fuel can be introduced into the liner just before the implosion without melting a significant amount of a pure frozen fuel layer. This approach is the most promising for high yield and gain with MagLIF.