1 research outputs found
Radiation hydrodynamics with backscatter and beam spray in gas filled hohlraum experiments at the National Ignition Facility
Several experiments using either CO or propane gas
filled halfraums [i.e. hohlraums with a single laser entry hole (LEH)] have
been shot at the National Ignition Facility (NIF) in a joint Los
Alamos/Livermore collaboration. The experiments have been modeled by the
Lasnex code. The possibility of beam spray due to filamentation of the
incident laser beam is assessed through simulations which parametrically
decrease the f-number of the beam at times of high intensity. The
uncertainty in heat transport is evaluated through parametric variations in
the electron thermal flux limit (fe). Each calculation in the resulting two
parameter set is post-processed to simulate outputs which can be compared
with Dante detector results for the soft X-ray flux through the LEH, and
gated, framed images of hard X-rays (FXI) through the hohlraum side walls.
Simulations which well match the data for both gases indicate that the laser
energy is penetrating the gas filled hohlraum even towards the end of the
pulse. This suggests that the gas fill is useful in keeping the hohlraum
open to laser energy throughout the pulse