Abstract Details
Multiple-Picket, Low-Adiabat Cryogenic Fuel Compression on OMEGA
Author: Valeri N Goncharov
Requested Type: Oral Only
Submitted: 2009-03-26 08:15:29
Co-authors: T. C. Sangster, T. R. Boehly, R. L. McCrory, D. D. Meyerhofer, P. B. Radha, V. A. Smalyuk, and S. Skupsky
Contact Info:
Laboratory for Laser Energetics
250 East River Road
Rochester, NY 14623
USA
Abstract Text:
Low-adiabat cryogenic-target-compression experiments are currently performed on the OMEGA laser to study physics of fuel assembly in inertial confinement fusion. Both continuous-pulse and multiple-picket designs have been used in these experiments. Success of continuous-pulse designs relies on accurate modeling of the nearly adiabatic compression wave created by a gradual rise in laser intensity. Inaccuracies in modeling EOS and laser coupling make it difficult to prevent shock formation at the head of the compression wave as it travels through the fuel. Such shock formation excessively raises fuel adiabat and reduces final compression. Premature shock formation is very hard to detect experimentally since the compression wavefront travels behind the first shock and is not visible to VISAR. To better control fuel adiabat, a gradual intensity rise region is replaced in a multiple-picket design with three pickets. This facilitates experimental shock tuning, as recently demonstrated in shock-velocity measurements performed on OMEGA.1 The required shock-timing accuracy can be achieved in this case by adjusting energies of each picket. As an additional advantage, the multiple-picket designs are less susceptible to the Rayleigh–Taylor instability since the intensity pickets produce an enhanced adiabat steepening at the ablation front, increasing the ablative stabilization of perturbations developed during the implosion. This talk will summarize recent results from cryogenic, multiple-picket implosions on OMEGA.
This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302, the University of Rochester, and the New York State Energy Research and Development Authority. The support of DOE does not constitute an endorsement by DOE of the views expressed in this article.
1T. R. Boehly et al., Phys. Plasmas 16, 056302 (2008).
Comments:
This abstract is submitted for an invited talk.