Constraining fundamental plasma physics processes using doped capsule implosions

Garbett, Warren; James, Steven; Kyrala, G. A.; Wilson, D. C.; Benage, J.F.; Wysocki, F. J.; Gunderson, Michael A.; Frenje, J. A.; Petrasso, R. D.; Glebov, V. Yu.; Yaakobi, B.

doi:10.1088/1742-6596/112/2/022016

Cited by 7 publications

(11 citation statements)

References 7 publications

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“…Previously published modeling of these implosions 4,5 identified a discrepancy between experimental and calculated yields using a 1-D integrated model described below.…”

Section: Introductionmentioning

confidence: 99%

The effects of laser absorption on direct-drive capsule experiments at OMEGA

et al. 2012

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The yield of an inertial confinement fusion capsule can be greatly affected by the inclusion of high-Z material in the fuel, either intentionally as a diagnostic or from mixing due to hydrodynamic instabilities. To validate calculations of these conditions, glass shell targets filled with a D 2 and 3 He fuel mixture were fielded in experiments with controlled amounts of pre-mixed Ar, Kr, or Xe. The experiments were fielded at the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using 1.0 ns square laser pulses having a total energy 23 kJ and direct drive illumination of shells with an outer diameter of $925 lm and a thickness of $5 lm. Data were collected and compared to one-dimensional integrated models for yield and burn-temperature measurements. This paper presents a critical examination of the calculational assumptions used in our experimental modeling. A modified treatment of laser-capsule interaction improves the match to the measured scattered laser light and also improves agreement for yields, burn-temperatures, and the fuel compression as measured by the ratio of two yields. Remaining discrepancies between measurement and calculation will also be discussed. V C 2012 American Institute of Physics. [http://dx

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“…Previously published modeling of these implosions 4,5 identified a discrepancy between experimental and calculated yields using a 1-D integrated model described below.…”

Section: Introductionmentioning

confidence: 99%

The effects of laser absorption on direct-drive capsule experiments at OMEGA

et al. 2012

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“…Observation of the resulting fuel stratification in the DT implosion, which upsets the initially optimal arrangement of equal number densities of D and T, in experiments [11] and kinetic simulations [12][13][14][15] have recently been reported. The targets with high-Z dopants show a particularly strong yield anomaly [6,7,16], suggesting that even stronger fuel stratification may take place.Perhaps the most intriguing physics aspect of interion-species diffusion in a collisional plasma is the role of thermo-diffusion, which, as its name suggests, is driven by the gradients of ion and electron temperatures. The novelty comes through as a sharp contrast to the better-known case of a neutral mixture, where thermo-diffusion is substantially less important than baro-diffusion, though often counteracts it [9].…”

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confidence: 99%

Thermo-diffusion in inertially confined plasmas

Kagan

Tang

2014

Physics Letters A

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In a plasma of multiple ion species, thermodynamic forces such as pressure and temperature gradients can drive ion species separation via inter-species diffusion. Unlike its neutral mix counterpart, plasma thermo-diffusion is found comparable to, or even much larger than, baro-diffusion. It is shown that such a strong effect is due to the long-range nature of the Coulomb potential, as opposed to short-range interactions in neutral gases. A special composition of the tritium and 3 He fuel is identified to have vanishing net diffusion during adiabatic compression, and hence provides an experimental test in which yield degradation is minimized during ICF implosions.In inertial confinement fusion (ICF), the central "hotspot" plasma, assembled by laser-driven spherical implosion [1], contains multiple ion species. Common combinations include low-Z fuel mixtures such as deuterium (D)/tritium (T) and D 3 He with possible addition of high-Z pusher ions, such as carbon or silicon, due to plastic or glass shell mixing [2,3] into the gas fill. Sometimes high-Z gas dopants such as Ar [4] or Kr [5] are intentionally introduced for diagnostic purposes, as well as to specifically study the pre-mix effects [6,7]. The powerful thermodynamic forces (e.g. pressure [8][9][10] and temperature gradients [9,10]) in an imploding target can drive ion species separation via inter-species diffusion. Observation of the resulting fuel stratification in the DT implosion, which upsets the initially optimal arrangement of equal number densities of D and T, in experiments [11] and kinetic simulations [12][13][14][15] have recently been reported. The targets with high-Z dopants show a particularly strong yield anomaly [6,7,16], suggesting that even stronger fuel stratification may take place.Perhaps the most intriguing physics aspect of interion-species diffusion in a collisional plasma is the role of thermo-diffusion, which, as its name suggests, is driven by the gradients of ion and electron temperatures. The novelty comes through as a sharp contrast to the better-known case of a neutral mixture, where thermo-diffusion is substantially less important than baro-diffusion, though often counteracts it [9]. According to statistical physics, thermo-diffusion strongly depends on the details of the collisional exchange between and within the species [10]. Due to the long range nature of Coulomb collisions in plasmas, as opposed to short range collisions between neutral particles, one may expect thermo-diffusion in plasmas and neutral mixtures to be fundamentally different. This difference becomes particularly striking with the observation that plasma baro-diffusion ratio k p is identical to its neutral counterpart [17].

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“…Equally important, in low-Z/high-Z mixtures, k T were found to attain large absolute values and slopes at small concentrations of the high-Z component [20]. Plasma thermo-diffusion may thus be potentially responsible for the anomalous yield reduction in doped capsule implosions [8,9] in addition to the laser absorption effects considered earlier [18].…”

Section: Inter-ion-species Diffusionmentioning

confidence: 96%

“…The central hot plasma in a spherical implosion contains multiple ion species, which can include both low-Z and high-Z elements [7,8,9,10,11]. Their relative concentrations can evolve substantially over the course of implosion due to inter-ion-species diffusion [12,13].…”

Section: Inter-ion-species Diffusionmentioning

confidence: 99%

“…Observation of the resulting fuel stratification in experiments [14,15,16,17] and fully kinetic simulations [3,4] have recently been reported. The targets with high-Z dopants show particularly pronounced yield anomalies [8,9,18], suggesting that even stronger fuel stratification may take place. In addition, this is the same diffusion process that underlies the atomic mixing at the shell/fuel interface.…”

Section: Inter-ion-species Diffusionmentioning

confidence: 99%

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Kinetic studies of ICF implosions

Kagan

Herrmann

Kim

et al. 2016

J. Phys.: Conf. Ser.

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Abstract. Kinetic effects on inertial confinement fusion have been investigated. In particular, inter-ion-species diffusion and suprathermal ion distribution have been analyzed. The former drives separation of the fuel constituents in the hot reacting core and governs mix at the shell/fuel interface. The latter underlie measurements obtained with nuclear diagnostics, including the fusion yield and inferred ion burn temperatures. Basic mechanisms behind and practical consequences from these effects are discussed.

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Constraining fundamental plasma physics processes using doped capsule implosions

Cited by 7 publications

References 7 publications

The effects of laser absorption on direct-drive capsule experiments at OMEGA

The effects of laser absorption on direct-drive capsule experiments at OMEGA

Thermo-diffusion in inertially confined plasmas

Kinetic studies of ICF implosions

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