57th Annual Meeting of the APS Division of Plasma Physics
Volume 60, Number 19
Monday–Friday, November 16–20, 2015;
Savannah, Georgia
Session CI3: ICF Stagnation and Burn
2:00 PM–5:00 PM,
Monday, November 16, 2015
Room: Oglethorpe Auditorium
Chair: Max Karasik, Naval Research Laboratory
Abstract ID: BAPS.2015.DPP.CI3.5
Abstract: CI3.00005 : Demonstration of $55\pm 7\mbox{-Gbar}$ Hot-Spot Pressure in Direct-Drive Layered DT Cryogenic Implosions on OMEGA
4:00 PM–4:30 PM
Preview Abstract
Abstract
Author:
S.P. Regan
(Laboratory for Laser Energetics, U. of Rochester)
Direct-drive ignition target designs for the National Ignition Facility
(NIF) require hot-spot pressures in excess of 100 Gbar. Only one-third of
the required pressure was inferred in earlier experimental campaigns
conducted on the 60-beam, 30-kJ, 351-nm OMEGA laser with direct-drive
implosions of layered DT cryogenic targets.\footnote{V. N. Goncharov \textit{et al}.,
Phys. Plasmas \textbf{21}, 056315 (2014).} Laser and target improvements
were implemented on OMEGA to increase the stagnation pressure, including a
set of phase plates to increase the laser irradiation uniformity on target
and a purified fuel with isotope composition reaching a 50:50 DT ratio.
Diagnostic improvements were made for a neutron burnwidth measurement with a
40-ps impulse response and a 16-channel Kirkpatrick--Baez microscope to
measure gated (30-ps) x-ray images of the core near peak compression with
6-$\mu $m resolution. The inferred volume-averaged, peak pressure in the
current campaign almost doubled to $55\pm 7$ Gbar with a neutron yield
approaching $5 \times 10^{13}$. Further target
performance improvements to reach hydrodynamic equivalence to ignition on
OMEGA require mitigation of cross-beam energy transfer (CBET), which reduces
the laser coupling. A proposed technique to reduce CBET by driving the
spherical target with overlapping laser beams having individual focal spots
smaller than the outside diameter of the target was investigated. The
diameter of the target was discretely varied from 800 to 1000 $\mu$m, while
the laser focal spot size was kept constant at 820~$\mu $m. The larger
targets driven with up to 30 kJ of laser energy used dynamic bandwidth
reduction, where the smoothing by spectral dispersion (SSD) is only applied
to the pickets. The smaller targets driven with 26 kJ of laser energy had
SSD on the entire pulse. This talk will summarize the results of this CBET
mitigation campaign and describe a path forward to achieve ignition
hydro-equivalence on OMEGA. This material is based upon work supported by
the Department of Energy National Nuclear Security Administration under
Award Number DE-NA0001944.\\[4pt]
In collaboration with V. N. Goncharov, T. C. Sangster, R. Betti, T. R. Boehly, M. J. Bonino, T. J. B. Collins, J. A. Delettrez, D. H. Edgell, R. Epstein, C. J. Forrest, D. H. Froula, V. Yu. Glebov, D. R. Harding, S. X. Hu, I. V. Igumenshchev, R. Janezic, J. H. Kelly, T. J. Kessler, T. Z. Kosc, S. J. Loucks, J. A. Marozas, F. J. Marshall, R. L. McCrory, P. W. McKenty, D. D. Meyerhofer, D. T. Michel, J. F. Myatt, P. B. Radha, W. Seka, W. T. Shmayda, A. Shvydky, S. Skupsky, C. Stoeckl, B. Yaakobi, (Laboratory for Laser Energetics, U. of Rochester); J. A. Frenje, M. Gatu Johnson, R. D. Petrasso (PSFC, MIT).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2015.DPP.CI3.5