Evolution of Neutron-Initiated Micro-Big-Bang in superfluid He 3B

TL;DR

This paper investigates the long-lived energy storage in superfluid helium-3 after neutron capture, proposing that vortex loops emitted from a hot spot carry energy to container walls, explaining prolonged energy retention.

Contribution

It introduces a novel scenario where vortex loops emitted from a hot spot in superfluid helium-3 explain long-term energy storage, resolving previous contradictions.

Findings

Vortex loops carry significant energy away from the hot spot.

Loops reach container walls and survive longer than bulk vortex tangles.

The proposed mechanism explains the observed long delay in energy dissipation.

Abstract

A nuclear capture reaction of a single neutron by ultra-cold superfluid $^3$He results in a rapid overheating followed by the expansion and subsequent cooling of the hot subregion, in a certain analogy with the Big Bang of the early Universe. It was shown in a Grenoble experiment that a significant part of the energy released during the nuclear reaction was not converted into heat even after several seconds. It was thought that the missing energy was stored in a tangle of quantized vortex lines. This explanation, however, contradicts the expected lifetime of a bulk vortex tangle, $10^{-5}-10^{-4}\,$s, which is much shorter than the observed time delay of seconds. In this Letter we propose a scenario that resolves the contradiction: the vortex tangle, created by the hot spot, emits isolated vortex loops that take with them a significant part of the tangle's energy. These loops quickly reach the container walls. The dilute ensemble of vortex loops attached to the walls can survive for a long time, while the remaining bulk vortex tangle decays quickly.