Diffusive tunneling of Gamow fuel ions in a mixture of fusion fuel and inert pusher

Tang, Xian-Zhu; Elder, Todd; McDevitt, C. J.; Guo, Zehua

doi:10.1209/0295-5075/123/65002

Cited by 2 publications

(1 citation statement)

References 32 publications

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“…More careful considerations would suggest the role of the pusher material type and the thickness of the inert pusher material that partitions the DT fuel. In particular, in the limit where the inert pusher material separating fuel segments becomes sufficiently thin, fast ions will be able to diffusively tunnel through the inert layer with little loss of energy, as discussed in [28]. In such a limit, Knudsen layer losses can be anticipated to be strongly mitigated.…”

Section: Introductionmentioning

confidence: 99%

Yield reduction via the Knudsen layer effect in a mixture of fuel and pusher material

McDevitt¹,

Tang²,

Guo³

2018

Plasma Phys. Control. Fusion

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Hydrodynamic mix in inertial confinement fusion capsules produces chunk mix between deuterium-tritium fuel and inert pusher materials. The characteristic size of the intermingled fuel and pusher materials can be rapidly reduced by fluid mix, especially when the streamlines of the flow field are chaotic. This leads to an increasing Knudsen number for the fuel segments and a decreasing size of the pusher remnant with respect to the fuel ion mean-free-path. The former exacerbates Knudsen layer yield degradation due to fast ion losses, while the latter tends to alleviate Knudsen layer yield reduction due to other kinetic effects such as diffusive tunneling.

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Section: Introductionmentioning

confidence: 99%

Yield reduction via the Knudsen layer effect in a mixture of fuel and pusher material

McDevitt¹,

Tang²,

Guo³

2018

Plasma Phys. Control. Fusion

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Diffusive tunneling in an isobaric but non-isothermal fuel-pusher mixture

et al. 2019

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The hydrodynamic mix of fusion fuel and inert pusher can simultaneously generate smaller fuel pockets and finer pusher layers that separate them. Smaller fuel pockets have greater local Knudsen numbers, which tend to exacerbate the Knudsen layer reactivity reduction. A thinner pusher layer separating the neighboring fuel pockets, on the other hand, can enable the diffusive tunneling of Gamow fuel ions through the pusher layer and hence alleviate the Knudsen layer reactivity degradation. Here, the diffusive tunneling phenomenon describes a random walk process by which the Gamow fuel ions from one fuel pocket can traverse the inert pusher layer to join a neighboring fuel pocket without losing much of their energy. This is made possible by the much slower collisional slowing down rate compared with the pitch angle scattering rate of light fuel ions with heavier pusher ions. In an isobaric target mixture where fuel and pusher segments can have distinct temperatures, due to their different compressibilities, the temperature effect on the critical pusher layer areal density below which diffusive tunneling can occur, which is a property of the hydrodynamic mix, is understood by computing the ion charge state distribution using a collisional radiative model. This information is fed into the collisionality evaluation, enabling a parametric scan of the diffusive tunneling physics in terms of the target pressure, fuel, and pusher temperatures. It is found that when the gold pusher layer has a temperature above 1 keV, the variation of the pusher temperature has little effect on the critical areal mass density below which diffusive tunneling can occur. If the pusher layer is 1 keV or below, the critical areal mass density rises sharply, indicating that for a stronger fuel-pusher temperature disparity, the onset of diffusive tunneling will be at an earlier stage of the hydrodynamic mix when the fuel-pusher mixing structures are of less reduced size.

show abstract

Diffusive tunneling of Gamow fuel ions in a mixture of fusion fuel and inert pusher

Cited by 2 publications

References 32 publications

Yield reduction via the Knudsen layer effect in a mixture of fuel and pusher material

Yield reduction via the Knudsen layer effect in a mixture of fuel and pusher material

Diffusive tunneling in an isobaric but non-isothermal fuel-pusher mixture

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