Probing high areal-density cryogenic deuterium-tritium implosions using downscattered neutron spectra measured by the magnetic recoil spectrometer

Frenje, J. A.; Casey, D. T.; Li, C. K.; Sèguin, F. H.; Petrasso, R. D.; Glebov, V. Yu.; Radha, P. B.; Sangster, T. C.; Meyerhofer, D. D.; Hatchett, S.; Haan, S.; Cerjan, C.; Landen, O. L.; Fletcher, K.; Leeper, R. J.

doi:10.1063/1.3304475

Cited by 94 publications

(64 citation statements)

References 20 publications

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“…The DSR has been measured by a suite of neutron spectrometers, primarily the MRS ( [2,5]) and nTOF instruments [6]. The yield is reported by the spectrometers, as well as by a collection of activation foils called NADS.…”

Section: Experimental Observations Of Itfx At the Nifmentioning

confidence: 99%

Performance metrics for inertial confinement fusion implosions: Aspects of the technical framework for measuring progress in the National Ignition Campaign

et al. 2012

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The National Ignition Campaign (NIC) uses non-igniting "THD" capsules to study and optimize the hydrodynamic assembly of the fuel without burn. These capsules are designed to simultaneously reduce DT neutron yield and to maintain hydrodynamic similarity with the DT ignition capsule.We will discuss nominal THD performance and the associated experimental observables. We will show the results of large ensembles of numerical simulations of THD and DT implosions and their simulated diagnostic outputs. These simulations cover a broad range of both nominal and offnominal implosions. We will focus on the development of an experimental implosion performance metric called the experimental ignition threshold factor (ITFX). We will discuss the relationship between ITFX and other integrated performance metrics, including the ignition threshold factor (ITF), the generalized Lawson criterion (GLC), and the hot spot pressure (HSP). We will then consider the experimental results of the recent NIC THD campaign. We will show that we can observe the key quantities for producing a measured ITFX and for inferring the other performance metrics. We will discuss trends in the experimental data, improvement in ITFX, and briefly the upcoming tuning campaign aimed at taking the next steps in performance improvement on the path to ignition on NIF. * Electronic address: spears9@llnl.gov

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Section: Experimental Observations Of Itfx At the Nifmentioning

confidence: 99%

Performance metrics for inertial confinement fusion implosions: Aspects of the technical framework for measuring progress in the National Ignition Campaign

et al. 2012

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“…• [13][14][15], also provide independent measurements of apparent DT T ion . Unless otherwise stated, the apparent T ion values discussed in this paper are the weighted averages from all reporting spectrometers for each implosion.…”

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confidence: 99%

“…Although the word "stagnation" is often used for this phase of the implosion, it is inappropriate as the DT and DD neutron spectra indicate significant remaining kinetic energy. Neutron spectrometers [6][7][8][9][10][11][12][13][14][15] provide directional measurements of DT and DD neutron spectra from which yield, burn-averaged ion temperatures T ion and areal densities ρR are obtained. Neutron activation detectors (NADs) [16] measure the unscattered DT yield Y DT .…”

mentioning

confidence: 99%

Indications of flow near maximum compression in layered deuterium-tritium implosions at the National Ignition Facility

Johnson¹,

Knauer²,

Cerjan³

et al. 2016

Phys. Rev. E

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An accurate understanding of burn dynamics in implosions of cryogenically layered deuterium (D) and tritium (T) filled capsules, obtained partly through precision diagnosis of these experiments, is essential for assessing the impediments to achieving ignition at the National Ignition Facility. We present measurements of neutrons from such implosions. The apparent ion temperatures T ion are inferred from the variance of the primary neutron spectrum. Consistently higher DT than DD T ion are observed and the difference is seen to increase with increasing apparent DT T ion . The line-of-sight rms variations of both DD and DT T ion are small, ∼150 eV, indicating an isotropic source. The DD neutron yields are consistently high relative to the DT neutron yields given the observed T ion . Spatial and temporal variations of the DT temperature and density, DD-DT differential attenuation in the surrounding DT fuel, and fluid motion variations contribute to a DT T ion greater than the DD T ion , but are in a one-dimensional model insufficient to explain the data. We hypothesize that in a three-dimensional interpretation, these effects combined could explain the results. DOI: 10.1103/PhysRevE.94.021202 At the National Ignition Facility (NIF) [1], cryogenically layered capsules of deuterium (D) and tritium (T) fuel contained in 2-mm-diam carbon-based shells are imploded through laser irradiation of a surrounding high-Z hohlraum [2,3]. The imploding DT fuel assembles and "stagnates" in a configuration with a cold high-density shell surrounding a low-density hot spot. Efficient conversion of shell kinetic energy to hot-spot thermal energy is an essential requirement to achieving ignition at the NIF [4,5]. At peak convergence, this ideally results in a spherically symmetric, cold, dense DT fuel shell with an areal density ρR of ∼1.5 g/cm 2 surrounding a ∼5-keV hot spot with ρR ∼ 0.3 g/cm 2 . Although the word "stagnation" is often used for this phase of the implosion, it is inappropriate as the DT and DD neutron spectra indicate significant remaining kinetic energy. Neutron spectrometers [6][7][8][9][10][11][12][13][14][15] provide directional measurements of DT and DD neutron spectra from which yield, burn-averaged ion temperatures T ion and areal densities ρR are obtained. Neutron activation detectors (NADs) [16] measure the unscattered DT yield Y DT . In this paper we focus on the ion "temperatures" from a more extensive set of experiments than previously published [2] and conclude that the fuel assembly during burn in layered DT implosions is not well described by detailed one-dimensional (1D) physics models and simulations. The leading hypothesis for the observed discrepancy between the data and the 1D description is significant disordered motion and the highly 3D nature of the assembly at burn.For a homogeneous stationary DT plasma in thermal equilibrium at ion temperature T thermal , the variance of the * Corresponding author: gatu@psfc.mit.edu DT neutron spectrum (in units of neutron energy) is given bywhere E n is th...

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“…A detailed description of this diagnostic is given in Ref. [1][2][3]. Briefly the MRS has three main components.…”

Section: Nif Absolute Neutron Measurementsmentioning

confidence: 99%

Absolute measurement of the DT primary neutron yield on the National Ignition Facility

Leeper

Bleuel

Frenje

et al. 2013

EPJ Web of Conferences

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Abstract. The measurement of the absolute neutron yield produced in inertial confinement fusion target experiments conducted on the National Ignition Facility (NIF) is essential in benchmarking progress towards the goal of achieving ignition on this facility. This paper describes three independent diagnostic techniques that have been developed to make accurate and precise DT neutron yield measurements on the NIF.

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Probing high areal-density cryogenic deuterium-tritium implosions using downscattered neutron spectra measured by the magnetic recoil spectrometer

Cited by 94 publications

References 20 publications

Performance metrics for inertial confinement fusion implosions: Aspects of the technical framework for measuring progress in the National Ignition Campaign

Performance metrics for inertial confinement fusion implosions: Aspects of the technical framework for measuring progress in the National Ignition Campaign

Indications of flow near maximum compression in layered deuterium-tritium implosions at the National Ignition Facility

Absolute measurement of the DT primary neutron yield on the National Ignition Facility

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