Response to “Comment on ‘Species separation in inertial confinement fusion fuels’” [Phys. Plasmas 20, 044701 (2013)]

Bellei, C.; Amendt, Peter; Wilks, S. C.; Casey, D. T.; Li, C. K.; Petrasso, R. D.; Welch, D. R.

doi:10.1063/1.4799821

Cited by 8 publications

(3 citation statements)

References 8 publications

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“…from pure-D 2 implosions, and with 1D hydrodynamics simulations where species separation could not be taken into account. However, the ion-kinetic simulations that we conducted [10] did not confirm that explanation, generating further discussion [11][12][13].…”

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confidence: 85%

Species separation and modification of neutron diagnostics in inertial-confinement fusion

Inglebert

Canaud

Larroche

2014

EPL

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The different behaviours of deuterium (D) and tritium (T) in the hot spot of marginally igniting cryogenic DT inertial-confinement fusion (ICF) targets are investigated with an ion Fokker-Planck model. With respect to an equivalent single-species model, a higher density and a higher temperature are found for T in the stagnation phase of the target implosion. In addition, the stagnating hot spot is found to be less dense but hotter than in the single-species case. As a result, the fusion reaction yield in the hot spot is significantly increased. Fusion neutron diagnostics of the implosion find a larger ion temperature as deduced from DT reactions than from DD reactions, in good agreement with NIF experimental results. ICF target designs should thus definitely take ion-kinetic effects into account.

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confidence: 85%

Species separation and modification of neutron diagnostics in inertial-confinement fusion

Inglebert

Canaud

Larroche

2014

EPL

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“…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.…”

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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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“…a) Current affiliation: Administration and Technology Center for Science and Engineering, Technology Management Division, Waseda University invention of the cone-in-shell target [7] enables a heating laser to interact with close to the dense core without affecting the plasma surrounding the compressed fuel. However, only a small portion of the REB collides with the core because of its large divergence of the REB [8].…”

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confidence: 99%

Simple Analysis of the Laser-to-Core Energy Coupling Efficiency with Magnetized Fast Isochoric Laser Heating

Sakata

Johzaki

Lee

et al. 2019

Plasma and Fusion Research

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In this study, we have demonstrated the enhancement of laser-to-core energy coupling using magnetized fast isochoric laser heating on the GEKKO-LFEX laser facility. We achieved a maximum coupling of 8% by applying an external magnetic field, and the coupling gradually degraded with increasing energy of the heating laser, maintaining the pulse duration and the spot diameter constant. The obtained energy couplings are consistent with those obtained using simple calculation models. The models predict that an energy coupling of 20% -35% can be achieved by an ignition-scale core exhibiting a moderate guiding field and heating laser intensity.

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Response to “Comment on ‘Species separation in inertial confinement fusion fuels’” [Phys. Plasmas 20, 044701 (2013)]

Abstract: The claims made in the preceding Comment are categorically refuted. Further evidence to support the conclusions of our original paper is herein provided.

Cited by 8 publications

References 8 publications

Species separation and modification of neutron diagnostics in inertial-confinement fusion

Species separation and modification of neutron diagnostics in inertial-confinement fusion

Thermo-diffusion in inertially confined plasmas

Simple Analysis of the Laser-to-Core Energy Coupling Efficiency with Magnetized Fast Isochoric Laser Heating

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