Physics – Plasma Physics
Scientific paper
Nov 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996aps..dpp.7ia02a&link_type=abstract
American Physical Society, Division of Plasma Physics Meeting, November 10-15, 1996, abstract #7IA.02
Physics
Plasma Physics
Scientific paper
Efforts are underway to diagnose and control x-ray drive asymmetry in Nova hohlraums. Controlling time-integrated, lowest-order P2 flux asymmetry on target is conventionally accomplished by displacing the laser beams outward or inward along the hohlraum symmetry axis. A novel method to control P2 with fixed laser beams is to use a pair of axial gold discs of varying radii to partially block the laser-entrance-hole (LEH) from the view of the capsule. Some advantages in using axial discs include the prospect for added drive on target, the potential for P4 control when used in tandem with laser pointing, and possibly reduced time-dependent P_2(t) flux asymmetry swings at early time. Neutron-based diagnostics have provided some suggestion of increased drive, but a more direct measure of drive enhancement on target is with use of backlit, low-density (0.3 g/cc) foam balls. In this scheme, the ablatively-driven, inwardly propagating shock is imaged in time using backlighting from an irradiated Ti disc placed outside of the hohlraum. The benefit in using low-density surrogate targets is an amplified shock motion which enables easier detection of both average shock motion (drive) and distortion (flux asymmetry). Experiments and calculations are in excellent agreement over a nearly 20 eV enhancement in peak drive in the presence of axial gold discs. Measurements of lower-order distortion, P_2(t) and P_4(t), versus time for several laser pointings using this technique have also been carried out and show good agreement between experiment and simulations. Efforts to further control time-dependent flux asymmetry using beam-phasing techniques on Nova, as will be required on the National Ignition Facility, are under development. Current designs indicate a nearly factor of three reduction in P_2(t) variations and significant control of time-integrated P4 flux asymmetry with modest cone separation.
No associations
LandOfFree
New Methods for Controlling and Diagnosing Hohlraum Drive Asymmetry on Nova does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with New Methods for Controlling and Diagnosing Hohlraum Drive Asymmetry on Nova, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and New Methods for Controlling and Diagnosing Hohlraum Drive Asymmetry on Nova will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1146720