Probing helium interfaces with light scattering : from fluid mechanics to statistical physics

TL;DR

This paper explores helium droplet formation in different physical contexts using light scattering, highlighting how helium's unique optical properties enable detailed analysis of fluid mechanics and statistical physics phenomena.

Contribution

It introduces novel experimental approaches to study helium interfaces via light scattering, emphasizing helium's near-unity refractive index to reduce multiple scattering effects.

Findings

Helium droplets can be effectively studied using light scattering techniques.

The near-unity refractive index of helium minimizes multiple scattering issues.

Experimental results provide insights into helium's fluid mechanics and condensation processes.

Abstract

We have investigated the formation of helium droplets in two physical situations. In the first one, droplets are atomised from superfluid or normal liquid by a fast helium vapour flow. In the second, droplets of normal liquid are formed inside porous glasses during the process of helium condensation. The context, aims, and results of these experiments are reviewed, with focus on the specificity of light scattering by helium. In particular, we discuss how, for different reasons, the closeness to unity of the index of refraction of helium allows in both cases to minimise the problem of multiple scattering and obtain results which it would not be possible to get using other fluids.