Uniformity of fuel target implosion in Heavy Ion Fusion

TL;DR

This paper discusses the importance of implosion uniformity in heavy ion fusion, explores the dynamics of fuel hotspot stagnation, and reviews mitigation techniques like wobbling beam illumination to achieve stable, uniform target implosion.

Contribution

It provides a detailed analysis of implosion uniformity requirements and introduces wobbling heavy ion beam techniques to reduce non-uniformities in inertial confinement fusion.

Findings

Implosion uniformity should be less than a few percent for steady operation.

Fuel hotspot stagnation enhances vorticity, affecting implosion dynamics.

Wobbling heavy ion beams can reduce non-uniformity and mitigate Rayleigh-Taylor instability.

Abstract

In inertial confinement fusion the target implosion non-uniformity is introduced by a driver beams' illumination non-uniformity, a fuel target alignment error in a fusion reactor, the target fabrication defect, et al. For a steady operation of a fusion power plant the target implosion should be robust against the implosion non-uniformities. In this paper the requirement for the implosion uniformity is first discussed. The implosion uniformity should be less than a few percent. A study on the fuel hotspot dynamics is also presented and shows that the stagnating plasma fluid provides a significant enhancement of vorticity at the final stage of the fuel stagnation. Then non-uniformity mitigation mechanisms of the heavy ion beam (HIB) illumination are also briefly discussed in heavy ion inertial fusion (HIF). A density valley appears in the energy absorber, and the large-scale density valley also works as a radiation energy confinement layer, which contributes to a radiation energy smoothing. In HIF a wobbling heavy ion beam illumination was also introduced to realize a uniform implosion. In the wobbling HIBs illumination, the illumination non-uniformity oscillates in time and space on a HIF target. The oscillating-HIB energy deposition may contribute to the reduction of the HIBs' illumination non-uniformity by its smoothing effect on the HIB illumination non-uniformity and also by a growth mitigation effect on the Rayleigh-Taylor instability.