Measurements of Wall Stagnation in Gas-Filled ICF Hohlraums

Conference · Fri Aug 22 04:00:00 UTC 2003

OSTI ID:15004898

Turner, R E; Eder, D C; Dewald, E L; Wallace, R J; Amendt, P A; Pollaine, S M; Landen, O L; Thorpe, K; Pien, G

For ICF hohlraums driven by long pulses, such as will be needed for ignition on the NIF, the high-Z wall must be held back to avoid excessive laser spot motion and time-dependent symmetry swings. One means of accomplishing this is to fill the hohlraum with a low density, low-Z gas. We report on gas-wall interface characterization by axial x-ray backlighting and self-emission, on gas filled hohlraums fielded at the Omega facility. Up to 30 drive beams are fired, forming a single ring of illumination on the hohlraum wall to emulate the near 2D cylindrically symmetric NIF hohlraum drive conditions. We compare the observed motion with predictions. In addition, the gas-gold interface is Rayleigh-Taylor (R-T) unstable during deceleration. This R-T instability could be further exacerbated in NIF ignition hohlraums designed with intentionally roughened walls to provide smoothing of infrared heating used to prepare smooth DT ice layers in the capsule. We have therefore intentionally prepared initial perturbations on one half of the gold wall to quantify the amount of increased penetration, due to mix of the gold into the gas, at stagnation.

• Research Organization: Lawrence Livermore National Lab., CA (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 15004898
• Report Number(s): UCRL-JC-152389
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ACCELERATION
GOLD
HEATING
IGNITION
ILLUMINANCE
INSTABILITY
LASERS
OMEGA FACILITY
STAGNATION
SYMMETRY