|Ports (optics/electrical feedthroughs)||Four on the side of the cryostat *|
|Maximum port clear aperture||28 mm (77 K radiation shield limit)|
|Electrical connector (standard)||10 pint low-voltage electrical connector|
|Optic axis height||20 mm|
|Headroom (when cold)||77 mm|
|(Helium temperature) cold plate diameter||250 mm|
|Liquid helium capacity||9.5 litres|
|Liquid nitrogen capacity||10.0 litres|
|Hold time, subsequent fill (typical,not including initial fill)||60-80 days (ports blanked, no wiring)|
|21-28 days (reduced band mm detector)|
|14-21 days (broadband mm detector)|
|Liquid nitrogen hold time (approx)||>3 days|
|Cryostat diameter||365 mm|
|Cryostat height (excluding lifting handle)||710 mm|
|Mass (empty)||??? kg|
This dual reservoir cryostat is the largest non-bespoke cryostat that we manufacture. It has a 77 K liquid nitrogen Dewar and jacket, with an intermediate 40 K cold helium gas cooled radiation shield. This surrounds a central 4.2 K liquid helium Dewar. The liquid nitrogen hold time is over three days enabling this cryostat to be used in environments where minimal user intervention is required. A liquid helium hold time of up to twenty eight days is typical when this cryostat is used as a reduced band mm wave detector.
Readying the cryostat for operation by evacuating and cooling to liquid helium temperature, takes about one day. This includes a twenty four hour liquid nitrogen pre-cool. It is recommended that sufficient time be allowed to pre-cool the cryostat so that the gas cooled radiation shield has time to reach 77K before the liquid helium is transferred into the cryostat. A shorter pre-cool can be carried out, but this will require excessive use of the more expensive liquid helium cryogen.
Note that we regular customise the cryostat to suit customer applications. For example, extended radiation shields can be built that give a greater height above the 4.2K cold plate to accommodate larger apparatus. For example, a mini-refrigerator, or bespoke customer equipment can then be mounted in the cryostat.