The Cryospot uses a commercial off-the-shelf cryocooler to get down to slightly below liquid helium temperatures (typically below 3K). Cryocoolers or cryorefrigerators use a sealed reservoir of a cryogenic gas that is continually compressed, typically in two stages. In our case, the cryogenic gas is Helium, a very abundant gas in the universe but a dwindling (therefore expensive) resource on Earth. Cryocoolers operate in a "closed-cycle" manner, meaning that no external input of cryogen (whether in liquid or gas form) is required for normal operation. Cryocoolers come in two distinct varieties: Gifford McMahon (GM) and pulse-tube (PT), each with their own advantages.
Our helium sorption fridge is an add-on to the Cryospot systems, and operates in tandem with the cryocooler. The sorption fridge achieves a base temperature below 0.8K, which enables the operation of our nanowire detectors and enables other experiments that normally cannot function at 3K. Additionally, the sorption fridge holds a much more stable temperature than that of any typical cryocooler.