Mitigation of mode-one asymmetry in laser-direct-drive inertial confinement fusion implosions
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21ja008_full.pdf
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Author(s)
Mannion, O.M.
Igumenshchev, I.V.
Anderson, K.S.
Betti, R.
Campbell, E.M.
Cao, D.
Forrest, C.J.
Gatu Johnson, Maria
Glebov, V.Yu.
Goncharov, V.N.
Date Issued
January 2021
Journal
Physics of Plasmas
Publisher
AIP
Abstract
Nonuniformities present in the laser illumination and target in laser-driven inertial confi nement fusion experiments lead to an asymmetric compression of the target, resulting in an inefficient conversion of shell kinetic energy to thermal energy of the hot-spot plasma. In this paper, the effects of asymmetric compression of cryogenic deuterium tritium laser-direct-drive implosions are examined using a suite of nuclear and x-ray diagnostics on the OMEGA laser. The neutron-averaged hot-spot velocity (~uhs) and apparent ion temperature (Ti) asymmetry are determined from neutron time-of-flight measurements of the primary deuterium tritium fusion neutron energy spectrum, while the areal density (rhoR) of the compressed fuel surrounding the hot spot is inferred from measurements of the scattered neutron energy spectrum. The low-mode perturbations of the hot-spot shape are characterized from x-ray self-emission images recorded along three quasi-orthogonal lines of sight. Implosions with signifi cant mode-1 laser drive asymmetries show large hot-spot velocities (>100 km/s) in a direction consistent with the hot-spot elongation observed in x-ray images, measured Ti asymmetry, and rhoR asymmetry. Laser drive corrections have been applied through shifting the initial target location in order to mitigate the observed asymmetry. With the asymmetry corrected, a more-symmetric hot spot is observed with reduced ~uhs, Ti asymmetry, rhoR asymmetry, and a 30% increase in the fusion yield.
Description
Submitted for publication in Physics of Plasmas
MIT Department
Massachusetts Institute of Technology. Plasma Science and Fusion Center
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1063/5.0041554
