Multi-keV x-ray source development experiments on the National Ignition Facility
- Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
- Gray Research, Inc., 655 Discovery Drive, Suite 300, Huntsville, Alabama 35806 (United States)
- Defense Threat Reduction Agency, 8725 John J. Kingman Rd., Fort Belvoir, Virginia 22060-6201 (United States)
We report results from a five shot campaign carried out with Ar-Xe gas-filled targets at the National Ignition Facility (NIF). The targets were shot with {approx_equal}350 kJ of 3{omega} laser energy delivered with a 5 ns trapezoidal laser pulse. We report measured x-ray output from the target in different spectral bands both below and above 1.5 keV photon energies: We find yields of {approx_equal}20.5 kJ/sr with peak x-ray power approaching 4 TW/sr over all energies, as measured for the unique viewing angle of our detector, and {approx_equal}3.6 kJ/sr with peak x-ray power of 1 TW/sr for x-rays with energies >3 keV. This is a laser-to-x-ray conversion efficiency of 13{+-}1.3% for isotropic x-rays with energies >3 keV. Laser energy reflected by the target plasma for both inner and outer-cone beams is measured and found to be small, between 1% and 4% of the drive energy. The energy emitted in hard x-rays (with energies >25 keV) is measured and found to be {approx_equal}1 J/sr. Two-dimensional imaging of the target plasma during the laser pulse confirms a fast, volumetric heating of the entire target, resulting in efficient laser-to-x-ray conversion. Postshot simulations with a two-dimensional radiation-hydrodynamics code reproduce well the observed x-ray flux and fluence, backscattered light, and bulk target motion.
- OSTI ID:
- 21432232
- Journal Information:
- Physics of Plasmas, Vol. 17, Issue 8; Other Information: DOI: 10.1063/1.3458904; (c) 2010 American Institute of Physics; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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