<p>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&#xa0;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&#xa0;K the inner surface of the capillary is covered with a superfluid ⁴He film, which can thermally link stages of the&#xa0;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.</p>