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

Johnson, M. Gatu; Frenje, J. A.; Casey, D. T.; Li, C. K.; Séguin, F. H.; Petrasso, R. D.; Ashabranner, R.; Bionta, R. M.; Bleuel, D. L.; Bond, E.; Caggiano, J. A.; Carpenter, A.; Cerjan, C.; Clancy, T. J.; Doeppner, T.; Eckart, M. J.; Edwards, M. J.; Friedrich, S.; Glenzer, S. H.; Haan, S. W.; Hartouni, E. P.; Hatarik, R.; Hatchett, S.; Jones, O. S.; Kyrala, G. A.; Pape, S. Le; Lerche, R. A.; Landen, O. L.; Ma, T.; Mackinnon, A. J.; McKernan, M. A.; Moran, M. J.; Moses, E. I.; Munro, D. H.; McNaney, J. M.; Park, H. S.; Ralph, J. E.; Remington, B. A.; Rygg, J. R.; Sepke, S. M.; Smalyuk, V. A.; Spears, B. K.; Springer, P. T.; Yeamans, C. B.; Farrell, M.; Jasion, Daniel; Kilkenny, J. D.; Nikroo, A.; Paguio, R. R.; Knauer, J. P.; Glebov, V. Yu.; Sangster, T. C.; Betti, R.; Stoeckl, C.; Magoon, J.; Shoup, M. J.; Grim, G.; Kline, J. L.; Morgan, G. L.; Murphy, T. J.; Leeper, R. J.; Ruiz, C. L.; Cooper, G. W.; Nelson, A. J.

doi:10.1063/1.4728095

Cited by 126 publications

(34 citation statements)

References 23 publications

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“…For the 14.1 MeV, we obtained a total cross section, σ nCD2 = σ nC +2σ nD = 1.5 b+ 2×0.85 b =3.2 b. From the quaternary collisions we can also obtain an estimate of the areal density using the Down Scatter Ratio (DSR), the ratio of the number of neutrons with energy between 10 and 12 MeV (N 4 ) divided by the total number of ternary fusion reactions (N 3 -14.1 MeV neutrons): ρΛ=(20.4±0.6)DSR [23,21,51,48].…”

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Nuclear probes of an out-of-equilibrium plasma at the highest compression

et al. 2019

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We report the highest compression reached in laboratory plasmas using eight laser beams, E laser ≈12 kJ, τ laser =2 ns in third harmonic on a CD 2 target at the ShenGuang-II Upgrade (SGII-Up) facility in Shanghai, China. We estimate the deuterium density ρ D = 2.0 ± 0.9 kg/cm 3 , and the average kinetic energy of the plasma ions less than 1 keV. The highest reached areal density Λρ D =4.8 ± 1.5 g/cm 2 was obtained from the measured ratio of the sequential ternary fusion reactions (dd→t+p and t+d→α+n) and the two body reaction fusions (dd→ 3 He+n). At such high densities, sequential ternary and also quaternary nuclear reactions become important as well (i.e. n(14.1 MeV) + 12 C → n'+ 12 C* etc.) resulting in a shift of the neutron (and proton) kinetic energies from their birth values. The Down Scatter Ratio (DSR-quaternary nuclear reactions) method, i.e. the ratio of the 10-12MeV neutrons divided by the total number of 14.1MeV neutrons produced, confirms the high densities reported above. The estimated lifetime of the highly compressed plasma is 52 ± 9 ps, much smaller than the lasers pulse duration.

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Nuclear probes of an out-of-equilibrium plasma at the highest compression

et al. 2019

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“…The MRS yield has been compared to the NADs measurements, averaged over several different lines-of-sight, 21 which are also absolutely calibrated (the NIF nTOF detectors were calibrated with the MRS and NADs data and thus excluded in this comparison). 23 The yields determined from the MRS data, as a function of the activation data, are shown in Figure 3. Here, five different CD 2 foils were used with thickness ranging from 47 to 259 μm.…”

Section: Mrs Measurements Of the Yield On Omega And The Nifmentioning

confidence: 99%

Measuring the absolute deuterium–tritium neutron yield using the magnetic recoil spectrometer at OMEGA and the NIF

Casey

Frenje

Johnson

et al. 2012

Review of Scientific Instruments

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A magnetic recoil spectrometer (MRS) has been installed and extensively used on OMEGA and the National Ignition Facility (NIF) for measurements of the absolute neutron spectrum from inertial confinement fusion implosions. From the neutron spectrum measured with the MRS, many critical implosion parameters are determined including the primary DT neutron yield, the ion temperature, and the down-scattered neutron yield. As the MRS detection efficiency is determined from first principles, the absolute DT neutron yield is obtained without cross-calibration to other techniques. The MRS primary DT neutron measurements at OMEGA and the NIF are shown to be in excellent agreement with previously established yield diagnostics on OMEGA, and with the newly commissioned nuclear activation diagnostics on the NIF.

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“…The Specs all employ the same JAC Black detector assembly, a four channel detector opposite a centralized scintillator 17 , which has been optimized for measurement of the downscatter fraction. The design driver for this assembly was to reduce mass to a minimum within a radial boundary from the scintillator such that neutron re-scatter would not corrupt the downscatter ratio measurement.…”

Section: Ntof Spec Diagnosticsmentioning

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Engineering architecture of the neutron Time-of-Flight (nToF) diagnostic suite at the National Ignition Facility

et al. 2014

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This paper describes the engineering architecture and function of the neutron Time-of-Flight (nToF) diagnostic suite installed on the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). These instruments provide key measures of neutron yield, ion temperature, drift velocity, neutron bang-time, and neutron downscatter ratio.Currently, there are five nToFs on three collimated lines-of-site (LOS) from 18m to 27m from Target Chamber Center, and three positioned 4.5m from TCC, within the NIF Target Chamber but outside the vacuum and confinement boundary by use of re-entrant wells on three other LOS.NIF nToFs measure the time history and equivalent energy spectrum of reaction generated neutrons from a NIF experiment. Neutrons are transduced to electrical signals, which are then carried either by coaxial or Mach-Zehnder transmission systems that feed divider assemblies and fiducially timed digitizing oscilloscopes outside the NIF Target Bay (TB) radiation shield wall.One method of transduction employs a two-stage process wherein a neutron is converted to scintillation photons in hydrogen doped plastic (20x40mm) or bibenzyl crystals (280x1050mm), which are subsequently converted to an electrical signal via a photomultiplier tube or a photo-diode.An alternative approach uses a single-stage conversion of neutrons-to-electrons by use of a thin (0.25 to 2 mm) Chemical Vapor Deposition Diamond (CVDD) disc (2 to 24mm radius) under high voltage bias. In comparison to the scintillator method, CVDDs have fast rise and decay times (

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

Cited by 126 publications

References 23 publications

Nuclear probes of an out-of-equilibrium plasma at the highest compression

Nuclear probes of an out-of-equilibrium plasma at the highest compression

Measuring the absolute deuterium–tritium neutron yield using the magnetic recoil spectrometer at OMEGA and the NIF

Engineering architecture of the neutron Time-of-Flight (nToF) diagnostic suite at the National Ignition Facility

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