Dilution Refrigeration
3He-4He DilutionThe CryostatDetails of the CryostatPicturesFridge Links


Above is the 400 microwatt dilution fridge. It is completely open with all of the fridge components visible. The detectors are placed into the copper cylinder or "can" at the bottom of the image. Other larger cans fit over each other and each exist at a higher temperature then the smallest can.

Before installing the detectors, a temporary clean room must be placed around the bottom of the fridge to prevent contaminants from interfering with the tower electronics. Seen above is the 75 fridge with the clean room being installed.

Above is a retired "tower", which contains the detectors and the cold hardware and electronics.

This image is taken from the bottom of the 75 fridge showing the tower installed in the cans. Note the multiple layers of cans with the detectors in the middle.

In order to create a very good vacuum seal at extremely low temperatures an indium wire is placed around the bottom can of the fridge. This can closes the fridge with the tower inside. When The can is screwed into the rest of the fridge the indium wire is squeezed and forms a near perfect seal. IN normal temperatures a rubber O-ring is used, however at cryogenic temperatures the rubber hardens and indium must be used.

The above pictures show the bottom can with indium about to be put on the 75 fridge. The flat electronic components are squets, cold hardware devices that help read the detectors. The ribbon like cables coming out of the image are called striplines, which take the data from the squets to the data collection electronics.

Here are just some of the devices and electric components that provided information about he fridge and collect data from the striplines.

The above images shows the 75 fridge completely closed, with the outer vacuum chamber (OVC) in blue, which prevents heat transfer from the room to the inner components in order to keep the fridge old. The metal casing holds the yellow "lead castle" that begins at the bottom of the fridge. The lead castle is made of lead bricks and it helps to absorb radiation to prevent the detection of background noise.