Neutron yield study of direct-drive, low-adiabat cryogenic D{sub 2} implosions on OMEGA laser system

Journal Article · Sun Nov 15 04:00:00 EST 2009 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3259355· OSTI ID:21274270

Hu, S X; Radha, P B; Marozas, J A; Betti, R; Collins, T J. B.; Craxton, R S; Delettrez, J A; Edgell, D H; Epstein, R; Goncharov, V N; Igumenshchev, I V; Marshall, F J; McCrory, R L; Meyerhofer, D D; Regan, S P; Sangster, T C; Skupsky, S; Smalyuk, V A; Elbaz, Y; Shvarts, D ^[1]

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1. Laboratory for Laser Energetics, University of Rochester, 250 E. River Road, Rochester, New York 14623 (United States)

Neutron yields of direct-drive, low-adiabat ({alpha}{approx_equal}2 to 3) cryogenic D{sub 2} target implosions on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] have been systematically investigated using the two-dimensional (2D) radiation hydrodynamics code DRACO[P. B. Radha et al., 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 {mu}m), low-{alpha}, cryogenic targets. The 2D simulations of thin-shell implosions track experimental measurements for different target conditions and peak laser intensities ranging from 2.5x10{sup 14}-6x10{sup 14} W/cm{sup 2}. 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 {mu}m) 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 {mu}m offset and ice-roughness of {sigma}{sub rms}<3 {mu}m are required.

• OSTI ID: 21274270
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 11 Vol. 16; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DEUTERIUM
FUSION YIELD
LASER IMPLOSIONS
LASERS
NEUTRONS
PLASMA SIMULATION
THERMONUCLEAR REACTORS