Effect of 'wandering' and other features of energy transfer by fast electrons in a direct-drive inertial confinement fusion target

TL;DR

This paper theoretically investigates how the 'wandering' of fast electrons in the corona of ICF targets reduces their negative impact on target compression, showing only a small fraction of electrons reach the core.

Contribution

It introduces a model accounting for electron wandering in corona, demonstrating its effect on energy transfer and fuel compression in ICF targets.

Findings

Only 12% of fast electrons reach the compressed core.

Wandering significantly decreases the negative impact of fast electrons.

Energy distribution to the target is altered, reducing fuel compression loss.

Abstract

The heating of inertial confinement fusion (ICF) target by fast electrons, which are generated as a result of laser interaction with expanding plasma (corona) of a target, is investigated theoretically. It is shown that due to remoteness of the peripheral region, where electrons are accelerated, a significant portion of these particles, moving in corona and repeatedly crossing it due to reflection in a self-consistent electric field, will not hit into the compressed part of target. Using the modern models of fast electron generation, it is shown that in a typical target designed for spark ignition, the fraction of fast electrons that can pass their energy to compressed part of target is enough small. Only 12% of the total number of fast electrons can do it. Such an effect of 'wandering' of fast electrons in corona leads to a significant decrease in a negative effect of fast electrons on target compression. Taking into account the wandering effect, the distribution of energy transmitted by fast electrons to different parts of target and the resulting reduction of deuterium-tritium (DT) fuel compression are established.