Spatially and Temporally Resolved Plasma Density and Temperature Estimations of 20+kJ Laser Heated MagLIF Gas Pipes at the NIF*

Magnetized Liner Inertial Fusion (MagLIF) is a three-stage inertial confinement fusion (ICF) concept, in which a fuel cell is axially magnetized, pre-heated, and compressed.  During the pre-heat phase the fuel temperature must raise several 100s of eV, in order to set the conditions needed for nuclear fusion. Laser pre-heating is a process that is commonly studied at the National Ignition Facility (NIF), where over 20kL of laser energy is used to drive a MagLIF relevant target and test the accuracy of pre-heat models [1]. This process produces a large expanding plasma that is imaged using a Gated X-Ray Detector (GXD). By assuming that the observed plasma is cylindrically symmetric and that the captured emission is from Bremsstrahlung radiation a three-dimensional map of the plasma’s density, and temperature can be estimated. These parameters had previously only been understood though simulations, as experimental attempts using spectroscopy and optical Thomson scattering had produced data of limited value. Results from this new technique reveal the hydrodynamic expansion of the plasma and effects of local heat transport in warm C5H12 (neopentane) and cryogenic D2 filled targets. Unmagnetized solutions compare well to HYDRA simulations, however magnetized target solutions suggest a large change in heat transport has taken place which may not be being properly modeled.