The trick

The trick of helium-flow dilution cryostats

The film [1] shows a series of neutron images taken on NEUTROGRAPH at ILL in 2005.

We can see the progressive dilution of the helium 3 droplets in helium 4 inside a capillary tube. The in situ observation of cold being produced in the D10 cryostat is possible because helium 4 is almost transparent to neutrons, whilst helium 3 is very opaque (isotopic effect).


  1. M. Enderle, S. Pujol, A. Hillenbach (Institut Laue-Langevin), A. Benoit (CRTBT CNRS) (2005), personal communication.