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Title: One-Megajoule, Wetted-FOam Target-Design Performance for the National Ignition Facility

Abstract

Wetted-foam, direct-drive target designs are a path to high-gain experiments on the National Ignition Facility (NIF). Wetted-foam designs take advantage of the increased laser absorption provided by the higher-atomic-number elements in a target ablator composed of plastic foam saturated with deuterium-tritium (DT). The increased laser coupling allows for more fuel to be driven with the same incident laser energy, resulting in increased hydrodynamic stability and target gain.

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Laboratory for Laser Energetics, University of Rochester
Sponsoring Org.:
USDOE
OSTI Identifier:
902858
Report Number(s):
DE/FC52/92SF19460-745
Journal ID: ISSN 1070-664X; PHPAEN; 2006-93; 1707; TRN: US0703272
DOE Contract Number:
FC52-92SF19460
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Conference: 48th Annual Meeting of the APS Division of Plasma Physics, Philadelphia, PA, 30 October-3 November 2006
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ABSORPTION; HYDRODYNAMICS; LASERS; PERFORMANCE; PHYSICS; PLASMA; PLASTIC FOAMS; STABILITY; TARGETS; US NATIONAL IGNITION FACILITY

Citation Formats

Collins, T.J.B., Marozas, J.A., Betti, R., Harding, D.R., McKenty, P.W., Radha, P.B., Skupsky, S., Goncharov, V.N., Knauer, J.P., and McCrory, R.L.. One-Megajoule, Wetted-FOam Target-Design Performance for the National Ignition Facility. United States: N. p., 2007. Web. doi:10.1063/1.2709859.
Collins, T.J.B., Marozas, J.A., Betti, R., Harding, D.R., McKenty, P.W., Radha, P.B., Skupsky, S., Goncharov, V.N., Knauer, J.P., & McCrory, R.L.. One-Megajoule, Wetted-FOam Target-Design Performance for the National Ignition Facility. United States. doi:10.1063/1.2709859.
Collins, T.J.B., Marozas, J.A., Betti, R., Harding, D.R., McKenty, P.W., Radha, P.B., Skupsky, S., Goncharov, V.N., Knauer, J.P., and McCrory, R.L.. Wed . "One-Megajoule, Wetted-FOam Target-Design Performance for the National Ignition Facility". United States. doi:10.1063/1.2709859.
@article{osti_902858,
title = {One-Megajoule, Wetted-FOam Target-Design Performance for the National Ignition Facility},
author = {Collins, T.J.B. and Marozas, J.A. and Betti, R. and Harding, D.R. and McKenty, P.W. and Radha, P.B. and Skupsky, S. and Goncharov, V.N. and Knauer, J.P. and McCrory, R.L.},
abstractNote = {Wetted-foam, direct-drive target designs are a path to high-gain experiments on the National Ignition Facility (NIF). Wetted-foam designs take advantage of the increased laser absorption provided by the higher-atomic-number elements in a target ablator composed of plastic foam saturated with deuterium-tritium (DT). The increased laser coupling allows for more fuel to be driven with the same incident laser energy, resulting in increased hydrodynamic stability and target gain.},
doi = {10.1063/1.2709859},
journal = {Physics of Plasmas},
number = ,
volume = 14,
place = {United States},
year = {Wed May 02 00:00:00 EDT 2007},
month = {Wed May 02 00:00:00 EDT 2007}
}
  • The NIF Target Area is designed for ICF experiments with the goal of fusion ignition. The Target Area must provide appropriate conditions before, during, and after each shot. The repeated introduction of large amounts of laser energy into the chamber and emission of fusion energy from a cryogenic target represent new challenges in ICF facility design. Prior to a shot, the facility provides proper illumination geometry, target chamber vacuum, and a stable platform for the target and its diagnostics. During a shot, the impact of the energy introduced into the chamber is minimized, and workers and the public are protectedmore » from excessive prompt radiation doses. After the shot, the residual radioactivation is managed to allow required accessibility. Tritium and other radioactive wastes are controlled and disposed. Diagnostic data is also retrieved, and the facility is readied for the next shot. The Target Area will accommodate yields up to 20 MJ, with a maximum credible yield of 45 MJ. The target area`s design lifetime is 30 years. The Target Area provides the personnel access needed to support experimentation employing precision diagnostics. The annual shot mix for design purposes is shown. Designing to this experimental envelope ensures the ability and flexibility to move through the experimental campaign to ignition efficiently.« less
  • Recent results are presented from two-dimensional LASNEX [G. B. Zimmerman and W. L. Kruer, Comments Plasmas Phys. Controlled Thermonucl. Fusion {bold 2}, 51 (1975)] calculations of the indirectly driven hohlraum and ignition capsules proposed for the National Ignition Facility (NIF). The calculations concentrate on two capsule designs, the baseline design that has a bromine-doped plastic ablator, and the beryllium design that has a copper-doped beryllium ablator. Both capsules have a cryogenic fuel layer. Primary emphasis in these calculations is placed upon robustness studies detailing various sensitivities. Because of computer modeling limitations these studies fall into two categories: those performed withmore » integrated modeling where the capsule, hohlraum, and laser rays all are modeled simultaneously with the laser power levels as the only energy input; and those performed in a capsule-only mode where an externally imposed radiative flux is applied to the exterior of the capsule, and only the capsule performance is modeled. Integrated modeling calculations address sensitivities to, e.g., the laser pointing; among other things, capsule-only calculations address yield degradation due to the growth of hydrodynamic instabilities seeded by initial surface roughnesses on the capsules. Limitations of the calculational models and directions for future research are discussed. The results of the robustness studies performed to date enhance the authors{close_quote} confidence that the NIF can achieve ignition and produce 10{endash}15 MJ of capsule yield with one or more capsule designs. {copyright} {ital 1996 American Institute of Physics.}« less
  • Shock ignition presents a viable path to ignition and high gain on the National Ignition Facility (NIF). In this paper, we describe the development of the 1D design of 0.5 MJ class, all-deuterium and tritium (fuel and ablator) shock ignition target that should be reasonably robust to Rayleigh-Taylor fluid instabilities, mistiming, and hot electron preheat. The target assumes 'day one' NIF hardware and produces a yield of 31 MJ with reasonable allowances for laser backscatter, absorption efficiency, and polar drive power variation. The energetics of polar drive laser absorption require a beam configuration with half of the NIF quads dedicatedmore » to launching the ignitor shock, while the remaining quads drive the target compression. Hydrodynamic scaling of the target suggests that gains of 75 and yields 70 MJ may be possible.« less
  • Laser plasma interaction (LPI) is a critical issue in ignition target design. Based on both scaling laws and two-dimensional calculations, this article describes how we can constrain a laser megajoule (LMJ) [J. Ebrardt and J. M. Chaput, J. Phys.: Conf. Ser. 112, 032005 (2008)] target design by mitigating LPI. An ignition indirect drive target has been designed for the 2/3 LMJ step. It requires 0.9 MJ and 260 TW of laser energy and power, to achieve a temperature of 300 eV in a rugby-shaped Hohlraum and give a yield of about 20 MJ. The study focuses on the analysis ofmore » linear gain for stimulated Raman and Brillouin scatterings. Enlarging the focal spot is an obvious way to reduce linear gains. We show that this reduction is nonlinear with the focal spot size. For relatively small focal spot area, linear gains are significantly reduced by enlarging the focal spot. However, there is no benefit in too large focal spots because of necessary larger laser entrance holes, which require more laser energy. Furthermore, this leads to the existence, for a given design, of a minimum value for linear gains for which we cannot go below.« less