Speaker
Rahul C. Shah
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/I1.203.pdf
Improving Direct-Drive Implosion Symmetry Using Three-Dimensional
X-Ray Tomography on OMEGA
R. C. Shah1, D. T. Michel1, I. V. Igumenshchev1, K. S. Anderson1, A. K. Davis2, D. H.
Edgell1, C. J. Forrest, D. H. Froula1, V. N. Goncharov1, D. W. Jacobs-Perkins1, S. P. Regan1,
A. Shvydky1, and E. M. Campbell1
1
Laboratory for Laser Energetics, University of Rochester, Rochester, NY, 14623, USA
2
NNSA Graduate Fellowship Program, Washington, DC, 20585, USA
Reducing low-mode nonuniformities of imploding targets has been identified as a critical
step to demonstrate conditions for laser-direct-drive (LDD) inertial confinement fusion
implosions that are hydrodynamically scaled to ignition designs for megajoule laser energy at
the National Ignition Facility.1 A series of well-diagnosed experiments were performed for
the 100-Gbar campaign on OMEGA,2 where the 3-D modes λ = 1, 2, and 3 of the imploding
target were tomographically recorded (within ±0.15% ) up to a convergence of 3 using four
lines-of-sight x-ray measurements of the ablation front.3 Measurements of the ablation
surface location show that the target modes are the result of two components: a dynamic part
that varies linearly with the beam-energy balance, and an approximately constant static part,
resulting from physical effects such as beam mispointing, mistiming, and uncertainties in the
beam energies.4 This technique was used to reduce the low-mode nonuniformities of a
low-adiabat implosion from 3.5-µm rms to 1-µm rms by adjusting the beam-energy balance
to compensate these static modes, which is an important demonstration for LDD. These
methods are currently applied to quantify the effect of the target offset on target modes, and
will be applied to cryogenic implosions to obtain improved performances. This material is
based upon work supported by the Department of Energy National Nuclear Security
Administration under Award Number DE-NA0001944, the University of Rochester, and the
New York State Energy Research and Development Authority. The support of DOE does not
constitute an endorsement by DOE of the views expressed in this article.
References
1. S. P. Regan et al., Phys. Rev. Lett. 117, 025001 (2016); 117, 059903(E) (2016).
2. V. N. Goncharov et al., Plasma Phys. Control. Fusion 59, 014008 (2017).
3. D. T. Michel et al., Rev. Sci. Instrum. 83, 10E530 (2012).
4. D. T. Michel et al., “Subpercent-Scale Control of 3-D Modes 1, 2, and 3 in Direct-Drive Configuration
on OMEGA,” submitted to Physical Review Letters.
