54th Annual Meeting of the APS Division of Plasma Physics
Volume 57, Number 12
Monday–Friday, October 29–November 2 2012;
Providence, Rhode Island
Session BI3: ICF Implosions, Diagnostics, Laboratory Shocks
9:30 AM–12:30 PM,
Monday, October 29, 2012
Room: Ballroom BC
Chair: Charles Nakhleh, Sandia National Laboratories
Abstract ID: BAPS.2012.DPP.BI3.4
Abstract: BI3.00004 : Neutron Spectroscopy on the National Ignition Facility
11:00 AM–11:30 AM
Preview Abstract
Abstract
Author:
J.P. Knauer
(Laboratory for Laser Energetics, U. of Rochester)
The performance of cryogenic fuel implosion experiments in progress at the
National Ignition Facility (NIF) is measured by an experimental threshold
factor\footnote{M. J. Edwards \textit{et al}., Phys. Plasmas \textbf{18}, 051003 (2011).}
(ITFX) and a generalized Lawson Criterion.\footnote{C. D. Zhou and R.
Betti, Phys. Plasmas \textbf{15}, 102707 (2008); P. Y. Chang\textit{ et al.}, Phys. Rev.
Lett. \textbf{104}, 135002 (2010); and R. Betti \textit{et al.}, Phys. Plasmas \textbf{17},
058102 (2010).\par } The ITFX metric is determined by the fusion yield and
the areal density of an assembled deuterium-tritium (DT) fuel mass. Typical
neutron yields from NIF implosions are greater than 10$^{14}$ allowing the
neutron energy spectrum to be measured with unprecedented precision. A NIF
spectrum is composed of neutrons created by fusion (DT, DD, and TT
reactions) and neutrons scattered by the dense, cold fuel layer. Neutron
scattering is used to determine the areal density of a NIF implosion and is
measured along four lines of sight by two neutron time-of-flight detectors,
a neutron imaging system, and the magnetic recoil spectrometer. An accurate
measurement of the instrument response function for these detectors allows
for the routine production of neutron spectra showing DT fuel areal
densities up to 1.3 g/cm$^{2}$. Spectra over neutron energies of 10 to 17
MeV show areal-density asymmetries of 20{\%} that are inconsistent with
simulations. New calibrations and analyses have expended the spectral
coverage down to energies less than the deuterium backscatter edge (1.5 MeV
for 14 MeV neutrons). These data and analyses are presented along with a
compilation of other nuclear diagnostic data that show a
larger-than-expected variation in the areal density over the cold fuel mass.
This work was supported by the U.S. Department of Energy Office of Inertial
Confinement Fusion under Cooperative Agreement No DE-FC52-08NA28302. In
collaboration with NIC.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.DPP.BI3.4