Spherical compression of an applied magnetic field in inertial confinement fusion

TL;DR

This paper presents an analytic model for understanding how external magnetic fields are compressed and shaped during laser-driven inertial confinement fusion, revealing effects on thermal insulation and alpha particle trapping.

Contribution

The authors develop a simple analytic model to evaluate the topology of compressed magnetic fields in inertial confinement fusion, highlighting the impact of ablation and initial field configurations.

Findings

Ablation amplifies the central magnetic field.

Radially bent fields at the hotspot edge reduce thermal insulation.

Mirror initial fields provide the greatest suppression of thermal losses.

Abstract

Applying an external magnetic field to laser-driven inertial confinement fusion implosions is a promising approach for enhancing fusion yield. The field is compressed with the plasma, producing a magnetized hotspot that anisotropically suppresses thermal losses and traps alpha particles, making performance sensitive to the compressed field orientation. We derive a simple, readily applicable analytic model that enables rapid evaluation of the compressed field topology and show that ablation into the hotspot amplifies the central field, while the ablated ice near the hotspot edge develops a decaying, radially bent field, with a discontinuity in the field direction. The radially bent field renders thermal insulation at the hotspot edge negligible and largely independent of the applied field strength, whereas insulation in the hotspot core still depends strongly on the applied field. Applying the model to non-axial initial field configurations, we find that an initially applied mirror field provides the greatest suppression, followed by the standard axial field.