This section gives an introduction on cryocooling. Why do we need cryocooling? Further it briefly describes the Gifford McMahon cycle.

We use cryocoolers to cool some of the  instruments down to liquid Nitrogen temperatures. 

• INGRID
• LIRIS (available from beginning 2003)

These are two of the instruments were cryocoolers are used. Ingrid is an infrared photo-imager, Liris is an infrared spectrograph.

Working Cryopumps.

Cryogenic pumping is the process of 'freezing' gas or vapour out of a vacuum onto  very cold surfaces.

Components:

The system consist of the following parts:

• Compressor

• Coldhead

• Helium flexlines

The coldhead is mounted in the instrument, the compressor sits in Ghril at this moment. In the future it will be moved down to the oilplant again. It will be better to move the compressor out of the dome area to stop 'heat contamination'.

Helium is pumped through the system by the compressor to extract the heat from the coldhead. Compressor and coldhead are connected with Helium flexlines. In the coldhead expansion of the helium takes place thus providing cooling. In Ingrid cooldown temperatures down to 68K are achieved. If further cooldown is required a second stage will be needed.

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Last Updated 07/06/2002, Michiel van der Hoeven