Disruption of superfluid helium film flow in a filling capillary

Journal article

Superfluid liquid ⁴He consists of superfluid and normal components. The superfluid component has zero viscosity and zero entropy, therefore flows without dissipation. The normal component carries heat and can produce a high velocity flow which leads to very high thermal conductivity. In neutron scattering and muon spectroscopy experiments with powder samples, 4He gas is often used as an exchange medium to thermalise the sample. Samples are usually cooled using a dilution refrigerator with installed capillaries which admit ⁴He into the experimental volume. Below 2 K the inner surface of the capillary is covered with a superfluid ⁴He film, which can thermally link stages of the dilution refrigerator with a catastrophic effect on its performance. In our experiment, we utilised a 0.1% mixture of ³He in ⁴He to disrupt the superfluid helium film flow and, as a result, significantly reduced the parasitic thermal flow to the experimental can. The addition of a small amount of ³He into ⁴He allows a significant improvement of thermal performance when using this technique in neutron scattering experiments at very low temperatures.

Authors: Jones, A; Kirichek, O; Horney, S; Lawson, C

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Springer Nature
• Journal: Journal of Low Temperature Physics
• Volume: 222
• Issue: 3
• Article number: 77
• Publication date: 2026-05-05
• Acceptance date: 2026-04-21
• DOI: 10.1007/s10909-026-03412-9
• EISSN: 1573-7357
• ISSN: 0022-2291
• Language: English
• Keywords: sample environment; superfluid helium; neutron scattering