Institute Science and Technology of Accelerating Systems

Cryogenics

The cryogenics group provides cooling for scientific equipment at very low temperatures, both at BE-IAS and at BESSY II. Among other things, two helium liquefiers are operated for the supply at 4.2 K and 1.8 K. 

The following are supplied with cryogenic helium: 
- three test stands for superconducting cavities at 1.8K, 
- all cryomodules at SEALab at 1.8 K and 
- two superconducting magnets (wavelength shifters) at BESSY at 4.2 K. 

The cryogenic infrastructure is continuously being expanded and adapted to changing requirements. Preparations are underway to set up the supply for a complete superconducting accelerator module to be tested.

The two superconducting magnets at BESSY use small coolers to permanently compensate for thermal losses in the helium bath.

Helium is an expensive commodity. Ideally, it should not leave the system circuits. Two 10,000 litre and one 2000 litre dewar are available for storing the cold inventory. Two 400m³ and one 75m³ tank are available for storing the hot inventory.

Two liquid nitrogen tanks are also available. The liquid nitrogen is used for
- pre-cooling the circuits in the helium liquefiers, 
- direct cooling of thermal radiation shields in the cryogenic equipment, 
- indirect cooling of thermal radiation shields via helium intermediate circuits,
- as well as the cooling of a cryogenic undulator to 77K level.
The liquid nitrogen is consumable and released into the atmosphere after the stored cold has been removed.

Figure 1: Insulated cable in production, detail

Figure 2: Liquid nitrogen tank blow-off

Figure 3: Temperature sensor mounted inside a valve box

Figure 4: Valve plate in production, detail