Science of Fusion Ignition on NIF

Goldstein, W. H.

doi:10.2172/1061032

Cited by 17 publications

(9 citation statements)

References 10 publications

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“…This type of measurement puts stringent constraints on the modelling of the implosion, in terms of characterizing ρR asymmetries and possible fuel-shell kinetic energy remaining at burn and stagnation. Understanding the origin of ρR asymmetries is an essential prerequisite for achieving ignition because nonspherical assembly of the main fuel can reduce the efficiency of converting shell kinetic energy to hot-spot thermal energy at stagnation, possibly leading to lower hot-spot pressure and reduced confinement [28]. In recent years, the increasing availability of 3D simulation tools (e.g., HYDRA) has made it possible to computationally assess the impact of 3D effects on the implosion dynamics and experimental observables [29].…”

Section: D Structures-low-mode ρR Asymmetriesmentioning

confidence: 99%

Diagnosing implosion performance at the National Ignition Facility (NIF) by means of neutron spectrometry

et al. 2013

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The neutron spectrum from a cryogenically layered deuterium-tritium (dt) implosion at the National Ignition Facility (NIF) provides essential information about the implosion performance. From the measured primary-neutron spectrum (13-15 MeV), yield (Y n) and hot-spot ion temperature (T i) are determined. From the scattered neutron yield (10-12 MeV) relative to Y n , the down-scatter ratio, and the fuel areal density (ρR) are determined. These implosion parameters have been diagnosed to an unprecedented accuracy with a suite of neutron-time-of-flight spectrometers and a magnetic recoil spectrometer implemented in various locations around the NIF target chamber. This provides good implosion coverage and excellent measurement complementarity required for reliable measurements of Y n , T i and ρR, in addition to ρR asymmetries. The data indicate that the implosion performance, characterized by the experimental ignition threshold factor, has improved almost two orders of magnitude since the first shot taken in September 2010. ρR values greater than 1 g cm −2 are readily achieved. Three-dimensional semi-analytical modelling and numerical simulations of the neutron-spectrometry data, as well as other data for the hot spot and main fuel, indicate that a maximum hot-spot pressure of ∼150 Gbar has been obtained, which is almost a factor of two from the conditions required for ignition according to simulations. Observed Y n are also 3-10 times lower than predicted. The conjecture is that the observed pressure and Y n deficits are partly explained by substantial lowmode ρR asymmetries, which may cause inefficient conversion of shell kinetic energy to hot-spot thermal energy at stagnation.

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Section: D Structures-low-mode ρR Asymmetriesmentioning

confidence: 99%

Diagnosing implosion performance at the National Ignition Facility (NIF) by means of neutron spectrometry

et al. 2013

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“…(6) was studied numerically for a wide variety of plasma conditions and over the entire range of areal density; an example calculation is shown in Figure 4. This secondary yield scaling appears to be accurate for both secondary products to within 10% in plasmas with D and 4 He with densities between 0.1 and 1 g/cc, temperatures between 0.1 and 10 keV, and deuterium fractions between 0.1 and 1. For deuterium- 3 He mixtures in this range, the agreement is within 20%.…”

Section: A the Impact Of Plasma Composition On Secondary Yield Produmentioning

confidence: 73%

“…3 Experimental study of the core temperature, areal density, and composition is critical to make progress towards ignition. 4 Nuclear fusion products have been used extensively to study the behavior of the high energy-density plasmas generated in ICF implosions. [5][6][7][8][9][10][11][12] The high sensitivity of thermonuclear fusion yield rate to plasma ion temperature and density 13 makes the nuclear reaction histories and profiles valuable for studying the core plasma.…”

Section: Introductionmentioning

confidence: 99%

Using multiple secondary fusion products to evaluate fuel ρR, electron temperature, and mix in deuterium-filled implosions at the NIF

et al. 2015

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In deuterium-filled inertial confinement fusion implosions, the secondary fusion processes D(3 He,p) 4 He and D(T,n) 4 He occur, as the primary fusion products 3 He and T react in flight with thermal deuterons. In implosions with moderate fuel areal density ($5-100 mg/cm 2), the secondary D-3 He reaction saturates, while the D-T reaction does not, and the combined information from these secondary products is used to constrain both the areal density and either the plasma electron temperature or changes in the composition due to mix of shell material into the fuel. The underlying theory of this technique is developed and applied to three classes of implosions on the National Ignition Facility: direct-drive exploding pushers, indirect-drive 1-shock and 2-shock implosions, and polar direct-drive implosions. In the 1-and 2-shock implosions, the electron temperature is inferred to be 0.65 times and 0.33 times the burn-averaged ion temperature, respectively. The inferred mixed mass in the polar direct-drive implosions is in agreement with measurements using alternative techniques. V

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“…Its development is motivated by flows that are transient and move between small and large K or contain multiple interacting components with different Knudsen numbers. One possible future application lies in inertial confinement fusion (ICF) capsule implosion studies [12][13][14]. Although the implosion dynamics is governed by hydrodynamic phenomena, the fusion fuel ions (deuterium and tritium (D/T)) can have large mean-free-paths, which leads to kinetic effects and might impact ignition [15][16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

“…One possible future application lies in inertial confinement fusion (ICF) capsule implosion studies [12][13][14]. Although the implosion dynamics is governed by hydrodynamic phenomena, the fusion fuel ions (deuterium and tritium (D/T)) can have large mean-free-paths, which leads to kinetic effects and might impact ignition [15][16][17][18][19][20][21]. At present, our code does not have ICF capabilities since the required physics input (e.g.…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional implosion simulations with a kinetic particle code

2017

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We perform two-dimensional (2D) implosion simulations using a Monte Carlo kinetic particle code. The application of a kinetic transport code is motivated, in part, by the occurrence of nonequilibrium effects in inertial confinement fusion (ICF) capsule implosions, which cannot be fully captured by hydrodynamic simulations. Kinetic methods, on the other hand, are able to describe both, continuum and rarefied flows. We perform simple 2D disk implosion simulations using one particle species and compare the results to simulations with the hydrodynamics code RAGE. The impact of the particle mean-free-path on the implosion is also explored. In a second study, we focus on the formation of fluid instabilities from induced perturbations. We find good agreement with hydrodynamic studies regarding the location of the shock and the implosion dynamics. Differences are found in the evolution of fluid instabilities, originating from the higher resolution of RAGE and statistical noise in the kinetic studies.

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Science of Fusion Ignition on NIF

Cited by 17 publications

References 10 publications

Diagnosing implosion performance at the National Ignition Facility (NIF) by means of neutron spectrometry

Diagnosing implosion performance at the National Ignition Facility (NIF) by means of neutron spectrometry

Using multiple secondary fusion products to evaluate fuel ρR, electron temperature, and mix in deuterium-filled implosions at the NIF

Two-dimensional implosion simulations with a kinetic particle code

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