DEVELOPMENT OF AN ADIABATIC DEMAGNETIZATION REFRIGERATOR FOR SIRTF

An adiabatic demagnetization refrigerator (ADR) is being developed for the Multiband Imaging Photometer for SIRTF (MIPS). This refrigerator will cool infrared bolometers to 0.1 K to allow background limited sensitivity across the wavelength range from 0.2 to ≈1.5 mm. Two ADRs have been built and tested to demonstrate the capabilities required for a space mission. One, a laboratory ADR, achieves a hold time of > 12 h at 0.1 K. Temperature stability of ≈ 3 μK r.m.s. is obtained by regulating the magnetic field. A method for growing durable salt pills has been developed, and a system for suspending them with Kevlar cords has been demonstrated to withstand accelerations of 30 g from 5 Hz to 1 kHz. A second, similar ADR will fly on a balloon borne telescope. A ferromagnetic shield and a reliable, solenoid activated mechanical heat switch have been developed for this refrigerator. Techniques for constructing low heat leak current leads will also be discussed. © 1990.