Characterizing Laser Preheat For Laser-Driven Magnetized Liner Inertial Fusion Using Soft X-Ray Emission

Laser heating of a gas in a cylindrical liner held in by a thin foil window is a critical process in the MagLIF (magnetized liner inertial fusion) concept [S. A. Slutz and R. A. Vesey, Phys. Rev. Lett. 108, 025003 (2012)]. Window burnthrough and gas heating for OMEGA scale MagLIF cylinders as a function of time have been determined using spectrally integrated soft x-ray diagnostics. Window laser absorption is classified in terms of the emitted x-rays from the window plasma as a function of laser energy and shows that the laser energy absorbed is weakly dependent on incident intensity. Radiation-hydrodynamic simulations overestimate the amount of laser energy absorbed by the window as evidenced by the increase in x-ray radiation across several photon energy bands compared to experiments. Gas temperatures inferred from soft x-ray emission from the front 1mm of the liner are shown to evolve in time in a similar manner to simulation predictions. Soft x-ray emission from the gas within the region of the liner that is normally imploded is shown to meet the 100eV requirements set by the initial point design for laser-driven MagLIF.