“Clean” helium – no more blocking sub-4 K cryostats

Prof. Conrado Rillo of the University of Zaragoza together with his colleagues and the Spanish research council have finally found a recipe for “clean” Helium. Some low temperature applications require temperatures below the condensation point of liquid helium at 4.2 K. This temperature can be achieved by pressing helium through fine capillary tubes. Upon exiting the capillary tube, it cools down to 3 K and below due to expansion. However, at these temperatures molecular hydrogen freezes, which is a normal, but hard to remove impurity in liquid helium. Prof. Rillo and his colleagues assumed that a great number of the known failures in cryogenic experiments could be traced to frozen hydrogen on capillary tubes. To verify this, they pumped helium through a capillary. It was clogged within only 10 hours and could only be made permeable again by heating it to over its melting point.

The scientists assumed that to prevent blocking altogether, the concentration of molecular hydrogen would have to be approximately 10 mio. times less than what can be found in commercially available helium gas (~99,9%). To achieve this degree of purity, in a two-stage process, impurities like oxygen and nitrogen are removed by condensation. An additional chemical getter absorbs the remaining hydrogen. Prof. Rillo and his group have been using this cleaning procedure for over a year now and have not had any blocking effects since.

The procedure was developed in cooperation with Quantum Design, USA. The group uses the Quantum Design Advanced Technology Purifier ATP30. Please contact us to get quotations on both the ATP30 and the chemical getter. Read the full publication to geht more details on the research results.

We look forward to discussing your application and the implementation possibilities of the ATP in your laboratory with you.