Continuous cooling from 10 to 4 K using a toroidal ADR Original Research Article

Future large infrared space telescopes will require cooling to 4 K to achieve background limited performance for submillimeter wavelengths. These observatories will require lifetimes of many years and will have relatively large cooling requirements making stored helium dewars impractical. We have designed and are building an adiabatic demagnetization refrigerator (ADR) for use in cooling relatively large loads (10–100 mW) at 4 K and rejecting that heat to a cryocooler operating at 10 K. The ADR magnet consists of eight short coils wired in series and arranged in a toroid to provide self shielding of its magnetic field. We will use gas gap heat switches to alternately connect the toroid to the cold load and the warm heat sink. A small continuous stage will maintain the cold end at 4 K while the main toroid is recycled.