Neutron spectrometry-An essential tool for diagnosing implosions at the National Ignition Facility (invited)

Journal Article · Mon Oct 15 00:00:00 EDT 2012 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4728095· OSTI ID:22093805

Johnson, M. Gatu; Frenje, J. A.; Casey, D. T.; Li, C. K.; Seguin, F. H.; Petrasso, R. ^[1]; Ashabranner, R.; Bionta, R. M.; Bleuel, D. L.; Bond, E. J.; Caggiano, J. A.; Carpenter, A.; Cerjan, C. J.; Clancy, T. J.; Doeppner, T.; Eckart, M. J.; Edwards, M. J.; Friedrich, S.; Glenzer, S. H.; Haan, S. W. ^[2] ; others, and

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1. Massachusetts Institute of Technology Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States)
2. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

DT neutron yield (Y{sub n}), ion temperature (T{sub i}), and down-scatter ratio (dsr) determined from measured neutron spectra are essential metrics for diagnosing the performance of inertial confinement fusion (ICF) implosions at the National Ignition Facility (NIF). A suite of neutron-time-of-flight (nTOF) spectrometers and a magnetic recoil spectrometer (MRS) have been implemented in different locations around the NIF target chamber, providing good implosion coverage and the complementarity required for reliable measurements of Y{sub n}, T{sub i}, and dsr. From the measured dsr value, an areal density ({rho}R) is determined through the relationship {rho}R{sub tot} (g/cm{sup 2}) = (20.4 {+-} 0.6) Multiplication-Sign dsr{sub 10-12MeV}. The proportionality constant is determined considering implosion geometry, neutron attenuation, and energy range used for the dsr measurement. To ensure high accuracy in the measurements, a series of commissioning experiments using exploding pushers have been used for in situ calibration of the as-built spectrometers, which are now performing to the required accuracy. Recent data obtained with the MRS and nTOFs indicate that the implosion performance of cryogenically layered DT implosions, characterized by the experimental ignition threshold factor (ITFx), which is a function of dsr (or fuel {rho}R) and Y{sub n}, has improved almost two orders of magnitude since the first shot in September, 2010.

• OSTI ID: 22093805
• Journal Information: Review of Scientific Instruments, Vol. 83, Issue 10; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
CALIBRATION
ELECTRON TEMPERATURE
INERTIAL CONFINEMENT
ION TEMPERATURE
NEUTRON DETECTION
NEUTRON SPECTRA
NEUTRON SPECTROMETERS
NEUTRON SPECTROSCOPY
PERFORMANCE
PLASMA DIAGNOSTICS
RECOILS
TARGET CHAMBERS
THERMONUCLEAR IGNITION
THERMONUCLEAR REACTORS
TIME-OF-FLIGHT METHOD
TIME-OF-FLIGHT SPECTROMETERS
US NATIONAL IGNITION FACILITY