ABSTRACT
This chapter discusses two-stage adiabatic demagnetization refrigerator (ADR), as well as Helium-3 backed, single-stage ADRs. ADRs are typically used in the temperature range from a few Kelvin down to a few millikelvin, and, depending upon heat load, common ADRs can offer cooling durations anywhere from a few minutes to on the order of a week. ADR cryostats produce the cooling by cycling the magnetic field applied to a paramagnetic refrigerant material. This material is commonly referred to as a “salt pill” since many of the materials used are paramagnetic salts. The beauty of an ADR is that its temperature can be regulated, in a straightforward manner, anywhere between the system’s base temperature and its launch temperature. In order to generate an elegant design solution, one must identify the requirements of the ADR system. Prototype components—including cryogenic detectors, feedhorn-waveguide assemblies, and the various electronics—are placed into laboratory cryostats for characterization and testing.
