52nd Annual Meeting of the APS Division of Plasma Physics
Volume 55, Number 15
Monday–Friday, November 8–12, 2010;
Chicago, Illinois
Session QI3: Direct-Drive ICF; X-Ray Diagnostics
3:00 PM–5:00 PM,
Wednesday, November 10, 2010
Room: Grand Ballroom EF
Chair: Christina Back, General Atomics
Abstract ID: BAPS.2010.DPP.QI3.3
Abstract: QI3.00003 : Absolute measurements of short-pulse, long-pulse, and capsule-implosion backlighter sources at x-ray energies greater than 10 keV
4:00 PM–4:30 PM
Preview Abstract
Abstract
Author:
Brian Maddox
(Lawrence Livermore National Laboratory)
Laser-generated x-ray backlighters with x-ray energies $>$ 10 keV
are
becoming essential diagnostic tools for many high energy density
experiments. Examples include studies of high areal density cores
for
ignition designs, mid- to high-Z capsule implosion experiments,
absolute
equation of state experiments, dynamic diffraction under extreme
pressures,
and the study of material strength. Significant progress has been
made
recently using short pulse lasers, coupled to metal foil targets
[1], and
imploding capsules for producing high energy backlighters.
Measuring the
absolute x-ray flux and spectra from these sources is required for
quantitative analysis of experimental data and for the design and
planning
of future experiments. We have performed an extensive series of
experiments
to measure the absolute x-ray flux and spectra on the Titan, Omega,
Omega-EP, and NIF laser systems, employing single-photon-counting
detectors,
crystal spectrometers, and multichannel differential filtering
(Ross-pair)
and filter stack bremsstrahlung spectrometers. Calibrations were
performed
on these instruments [2] enabling absolute measurements of
backlighter
spectra to be made from 10 keV to 1 MeV. Various backlighter
techniques that
generate either quasi-monochromatic sources or broadband
continuum sources
will be presented and compared. For Molybdenum K$\alpha $
backlighters at
x-ray energy of $\sim $17 keV we measure conversion efficiencies of
1.3x10$^{-4}$ using 1 $\mu $m wavelength short-pulse lasers at an
intensity
of $\sim $1x10$^{17}$ W/cm$^{2}$. This is a factor of $\sim $2
high than
using 0.3 $\mu $m wavelength long-pulse lasers at an intensity of
$\sim
$1x10$^{16}$ W/cm$^{2}$. Other types of backlighter targets
include capsule
implosion backlighters that can generate a very bright
``white-light''
continuum x-ray source and high-Z gas filled capsules that
generate a
quasi-line-source of x rays. We will present and compare the
absolute laser
energy to x-ray conversion efficiencies for these different
backlighter
techniques and give examples of the science experiments that they
enable.
Lawrence Livermore National Laboratory is operated by Lawrence
Livermore
National Security, LLC, for the U.S. Department of Energy,
National Nuclear
Security Administration under Contract DE-AC52-07NA27344.
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[1] H-S. Park, PoP, 15, 072705 (2008).
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[2] B. R. Maddox, RSI, submitted (2010).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2010.DPP.QI3.3