Description: NASA's future science missions to investigate the structure and evolution of the universe require efficient, very low temperature coolers for low noise detector systems. We propose to develop a highly efficient, lightweight Active Magnetic Regenerative Refrigeration (AMRR) system that can continuously provide remote/distributed cooling at temperatures of about 2 K with a heat sink at about 15 K. The AMRR system uses three novel design features to achieve a large cooling capacity and very high thermal efficiency: a vibration-free, reversible cryogenic circulator; innovative micromachined regenerators; and lightweight superconducting magnets. The superconducting magnet uses low-current superconducting YBCO tapes and a unique winding arrangement to enable an AMRR to achieve high thermal efficiency. In Phase I, we will develop a design for the superconducting magnet and its electrical, thermal, and structural support subsystems. Based on the performance characteristics of the magnet system, we will optimize the magnetic field in the AMRR to minimize the overall system size and mass. In Phase II, we will build a superconducting magnet and demonstrate the performance of a magnetic regenerator driven by this magnet under prototypical conditions. In Phase III, we will assemble an integrated AMRR system and demonstrate its performance.

Benefits: The proposed AMRR system will enable NASA to carry out future space astronomy missions that use cryogenic infrared, gamma ray, and X-ray detectors. These detectors need to operate at temperatures in the range of 4 K to below 1 K to reduce the thermal emission of the detectors themselves and to achieve high sensitivity and resolution. The vibration-free, lightweight AMRR can provide efficient cooling for these missions at the required temperature ranges. The fabrication technologies developed for the lightweight superconducting magnets can also be applied to the fabrication of advanced magnets for multistage ADRs, particle accelerators, and portable MRIs.

Military applications for the proposed magnetic cooler include cooling systems on space-based surveillance, missile detection, and missile tracking systems. Scientific applications include cooling systems for material microanalysis using X-ray microcalorimeter spectrometers, superconducting radio frequency cavities, superconducting cavities, and superconducting digital electronics.