Cryogenic cell

A cryogenic cell comprises a sealed external annular chamber, adapted to be maintained under vacuum which chamber surrounds an isothermal heat shield. A section of the shield is exposed and is adapted to make contact with a closed cycle cooler. The shield encloses a sealed inner chamber containing a solid/liquid refrigerant and also has a well in its upper region immediately above and in contact with the top of the inner chamber. The inner chamber is connected at its lower end to a section containing an adsorbent and the latter section is connected at is lower end to a further chamber suitable for the reception of a gamma radiation detector. The cryogenic cell is suitable for keeping the semi-conductor detector of a neutron borehole logging tool at the required low temperature. (author)