3He Insert

A. S. Scientific Products Ltd. manufactures a simplified version of a 3He insert for the Orange Cryostat. This Insert has been developed by the I. L. L. Sample Environment Laboratory.

The insert has the following characteristics

  • Maximum sample dimensions: diameter 42 mm, length 90 mm.
  • Minimum temperature: 400 mK
  • Pure Aluminium Calorimeter (A5), internal diameter 45 mm, external diameter 48 mm.

Hence, for temperatures down to 400 mK, the much more complex dilution systems can be avoided and this system, which is not more difficult to use than a Standard Orange Cryostat, can be operated by the users, avoiding the long preparation and cool-down times characteristic of Dilution Cryostats

Schematic view of the 3He insert

This insert features an extra cooling circuit, which uses the same 3He gas to cool the sample from room temperature to 4 K (see schematic view above). Temperatures between 4K and 0.4K are obtained by switching to the Joule - Thomson expansion circuit also shown above.

In this insert no exchange gas is required, not even for fast cool-down. Thermalisation is guaranteed in the insulation vacuum via sample holder conduction. When, for example, electric fields have to be applied to the sample this represents a significant advantage.

Nevertheless, it is always possible to use exchange gas in the sample chamber just as in a classical dilution unit. Cooling time is about 3 hours and the refrigerating power at 0.5 K is 300 µW.

In order to automate the cool-down procedure, a computer is used to control the various parameters (temperature, cold valve etc.) of the Orange Cryostat and to execute the different valve sequences of the gas handling equipment. There is also a graphical display of the temperature progress available to the operator.