Description: NASA's future science missions to investigate the structure and evolution of the universe require highly 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 in the range of 2 K with a heat sink at about 15 K. The AMRR system uses a vibration-free, reversible cryogenic circulator and Micromachined Active Magnetic Regenerators (MAMRs) to achieve a large cooling capacity and very high thermal efficiency. The MAMRs use an innovative flow channel configuration and novel micromachining technologies to achieve very high thermal and flow performance. In Phase I we proved the feasibility of our approach by demonstrating critical fabrication methods for the micromachined regenerator and its thermal and flow performance through detailed analysis. In Phase II we will build and demonstrate a full-scale micromachined regenerator for a prototype AMRR system that can provide 70 mW of cooling near 2 K. In Phase III we will demonstrate the operation of an AMRR system incorporating the MAMRs and Creare's innovative reversible cryogenic circulator.

Benefits: The 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, cryogenic particle detectors, and biomolecule mass spectrometry using superconducting tunnel junction detectors.

The proposed AMRR system will enable NASA to carry out future science missions that use cryogenic infrared, gamma ray, and X-ray detectors. Potential missions include the International X-Ray Observatory (IXO) and the Single Aperture Far-Infrared observatory (SAFIR). 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 magnetic regenerator can also be applied to the fabrication of advanced regenerators for mechanical cryocoolers.