Dynamic Hohlraums as x-ray sources in high-energy density science
- Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
The first demonstration of laser driven dynamic Hohlraums (LDDH) as a spectrally smooth backlighter source for opacity and temperature measurements through absorption spectrometry of materials in local thermodynamic equilibrium at temperatures >150 eV has been made. This is a crucial temperature regime for future astrophysics and ignition fusion experiments at the nearly completed National Ignition Facility (NIF) [E. I. Moses and C. R. Wuest, Fusion Sci. Technol. 47, 314 (2005)] at the Lawrence Livermore National Laboratory. The new backlighter consists of a LDDH filled with either krypton or argon that implodes to create an x-ray flash. The properties of this x-ray flash have been measured in experiments at the Omega laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] at the Laboratory for Laser Energetics in Rochester, New York, satisfying all requirements imposed by future experiments: (1) the emission spectrum extends to at least 5.5 keV, well above the maximum x-ray energy ({approx}3.5 keV) obtained from the previously ''best'' opacity backlighters (uranium M-shell emission backlighters); (2) the spectrum is smooth and featureless (intensity variation <6% rms), allowing absorption spectrometry through experimental samples; (3) the emission source size is sufficiently small (<50 {mu}m) for projection backlighting through future samples; (4) the emission is bright enough (and twice as bright as imploding hydrogen-filled capsules) for gated spectrometer measurements; (5) the emission duration is optimized ({approx_equal}100 ps) for the current and future generations of spectrometers; and (6) by using only a small number of beams with limited energy and symmetry for the backlighter (10 out of 60 beams in the Omega experiments), the majority of laser beams are left available for heating sample materials to >150 eV.
- OSTI ID:
- 21024735
- Journal Information:
- Review of Scientific Instruments, Vol. 79, Issue 1; Other Information: DOI: 10.1063/1.2804765; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ABSORPTION SPECTROSCOPY
ARGON
BEAMS
CAPSULES
EMISSION
EMISSION SPECTRA
ENERGY DENSITY
HYDROGEN
KRYPTON
LASERS
LAWRENCE LIVERMORE NATIONAL LABORATORY
OPACITY
PLASMA HEATING
SPECTROMETERS
TEMPERATURE MEASUREMENT
URANIUM
US NATIONAL IGNITION FACILITY
X RADIATION
X-RAY SOURCES