Construction techniques for adiabatic demagnetization refrigerators using ferric ammonium alum

We describe techniques used to fabricate the cold stage of an adiabatic dem agnetization refrigerator that uses the paramagnetic salt ferric ammonium a lum. We discuss the design of a leak-tight housing for the salt as well as a technique for growing ferric ammonium alum crystals that results in a hou sing filled with > 98% refrigerant. These techniques have proven to be reli able in creating robust single-stage refrigerators. Similar techniques can be used for the second stage of a dual-stage adiabatic demagnetization refr igerator. (C) 1999 Elsevier Science Ltd. All rights reserved.