Time-resolved measurements of the hot-electron population in ignition-scale experiments on the National Ignition Facility (invited)
- Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)
- Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
- National Security Technologies LLC, Livermore, California 94551 (United States)
In laser-driven inertial confinement fusion, hot electrons can preheat the fuel and prevent fusion-pellet compression to ignition conditions. Measuring the hot-electron population is key to designing an optimized ignition platform. The hot electrons in these high-intensity, laser-driven experiments, created via laser-plasma interactions, can be inferred from the bremsstrahlung generated by hot electrons interacting with the target. At the National Ignition Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng. 43, 2841 (2004)], the filter-fluorescer x-ray (FFLEX) diagnostic–a multichannel, hard x-ray spectrometer operating in the 20–500 keV range–has been upgraded to provide fully time-resolved, absolute measurements of the bremsstrahlung spectrum with ∼300 ps resolution. Initial time-resolved data exhibited significant background and low signal-to-noise ratio, leading to a redesign of the FFLEX housing and enhanced shielding around the detector. The FFLEX x-ray sensitivity was characterized with an absolutely calibrated, energy-dispersive high-purity germanium detector using the high-energy x-ray source at NSTec Livermore Operations over a range of K-shell fluorescence energies up to 111 keV (U K{sub β}). The detectors impulse response function was measured in situ on NIF short-pulse (∼90 ps) experiments, and in off-line tests.
- OSTI ID:
- 22308583
- Journal Information:
- Review of Scientific Instruments, Vol. 85, Issue 11; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BREMSSTRAHLUNG
ELECTRONS
FLUORESCENCE
GE SEMICONDUCTOR DETECTORS
HARD X RADIATION
IGNITION
INERTIAL CONFINEMENT
K SHELL
KEV RANGE
LASER RADIATION
PLASMA
RESPONSE FUNCTIONS
SENSITIVITY
SIGNAL-TO-NOISE RATIO
TIME RESOLUTION
US NATIONAL IGNITION FACILITY
X-RAY SOURCES
X-RAY SPECTROMETERS