Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Plasma Physics
Volume 67, Number 15
Monday–Friday, October 17–21, 2022; Spokane, Washington
Session GI01: Inertial Confinement Fusion I
9:30 AM–12:45 PM,
Tuesday, October 18, 2022
Room: Ballroom 100 A
Chair: Brian Spears, LLNL
Abstract: GI01.00005 : Control of low-mode drive asymmetry in an efficient long pulse low-density filled hohlraum*
11:30 AM–12:00 PM
Presenter:
Nobuhiko Izumi
(Lawrence Livermore Natl Lab)
Author:
Nobuhiko Izumi
(Lawrence Livermore Natl Lab)
Through a series of NIF experiments using subscale targets (5.75 mm diameter hohlraums, filled at 0.45 mg/cc He, and 980 um outer radius capsules), we demonstrated that a symmetric implosion using a long duration low-adiabat drive is possible. We confirmed the original prediction that the wall motion dynamics of the adiabat controlled 4 shock drive pulse is modified by its long low power (< 1 TW) trough acting to temporarily interrupt the ballistic wall expansion, allowing for adequate inner beam propagation even 14 ns after laser start. To simultaneously mitigate P2 and P4 drive asymmetry swings caused by the drift of the laser spots, a temporal beam staggering[1] (TBS) technique was employed.
Finally, we demonstrated successful mitigation of the time-integrated P2 asymmetry using cross beam energy transfer from outer to inner cone beams. In summary excellent symmetry control of the main intrinsic asymmetry modes P2 and P4 throughout the pulse is possible for long pulse low-density filled hohlraums.
[1]R. Turner et. al. Phys Plasmas 7 (2000) 333.
*This work performed under the auspices of U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-836614
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