Neutron yield study of direct-drive, low-adiabat cryogenic D2 implosions on OMEGA laser system

S. X. Hu, P. B. Radha, J. A. Marozas, R. Betti, T. J.B. Collins, R. S. Craxton, J. A. Delettrez, D. H. Edgell, R. Epstein, V. N. Goncharov, I. V. Igumenshchev, F. J. Marshall, R. L. McCrory, D. D. Meyerhofer, S. P. Regan, T. C. Sangster, S. Skupsky, V. A. Smalyuk, Y. Elbaz, D. Shvarts

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

Neutron yields of direct-drive, low-adiabat (α≈2 to 3) cryogenic D2 target implosions on the OMEGA laser system [T. R. Boehly, Opt. Commun. 133, 495 (1997)] have been systematically investigated using the two-dimensional (2D) radiation hydrodynamics code DRACO [P. B. Radha, Phys. Plasmas 12, 056307 (2005)]. Low-mode (ℓ≤12) perturbations, including initial target offset, ice-layer roughness, and laser-beam power imbalance, were found to be the primary source of yield reduction for thin-shell (5 μm), low-α, cryogenic targets. The 2D simulations of thin-shell implosions track experimental measurements for different target conditions and peak laser intensities ranging from 2.5 × 1014 -6 × 1014 W/cm2. Simulations indicate that the fusion yield is sensitive to the relative phases between the target offset and the ice-layer perturbations. The results provide a reasonable good guide to understanding the yield degradation in direct-drive, low-adiabat, cryogenic, thin-shell-target implosions. Thick-shell (10 μm) implosions generally give lower yield over clean than low-ℓ-mode DRACO simulation predictions. Simulations including the effect of laser-beam nonuniformities indicate that high-ℓ-mode perturbations caused by laser imprinting further degrade the neutron yield of thick-shell implosions. To study ICF compression physics, these results suggest a target specification with a ≤30 μm offset and ice-roughness of σrms <3 μm are required.

Original languageEnglish
Article number112706
Pages (from-to)112706
Number of pages1
JournalPhysics of Plasmas
Volume16
Issue number11
DOIs
StatePublished - 16 Dec 2009
Externally publishedYes

ASJC Scopus subject areas

  • Condensed Matter Physics

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