Cooling experiments to ultra-cold temperatures permits exceptionally sensitive measurements to be made. This enables the study of subjects from quantum computation to subtle variations in the cosmic microwave background (CMB). To date, there is only one practical technology which can continuously cool high power experiments below 200 milliKelvin, the Helium Dilution Refrigerator (DR). These refrigerators are extremely expensive, complex, power intensive, orientation sensitive (with respect to gravity) and require the increasingly rare isotope Helium-3. There is another technology used to achieve these temperatures, Adiabatic Demagnetization Refrigeration (ADR). ADR technology relies on the demagnetization of paramagnetic solids which cool in a decreasing magnetic field. Once the field is lowered to zero, the cooling energy is depleted, and thus, typical implementations provide non-continuous refrigeration at the cold stage. Continuous cooling, as needed for CMB experimentation, requires the integration of 2 or more refrigerators. This has been done by NASA and a few others. However, while the resulting Continuous ADRs (CADRs) have a number of very attractive characteristics, such as cryogen-free operations, they have provided very limited load capacity a fraction of common DRs - and therefore, have never been a commercially viable option for the laboratory researcher. We will address these shortcomings and deliver a high power CADR via innovative design and laboratory-specific optimization of each CADR sub component and mechanism. In Phase I, we will create the design of a CADR optimized for power handling. This design will include CAD development and a detailed mathematical model of the CADR, to predict system performance. The design will include several innovations required to achieve high cooling for reasonable cost. A successful Phase I design will have a predicted cooling power exceeding 200microwatts at 100mK. In Phase II, we will develop and demonstrate a prototype system. The commercial applications of the high power CADR include researchers in CMB astronomy, quantum computing, and other fields where more reliable and affordable access to ultra-low temperatures is desired.
Keywords: Cosmic Microwave Background, CMB, Adiabatic Demagnetization Refrigerator, Low Temperature, Continuous Adiabatic Demagnetization Refrigerator, Dilution Refrigerator, Magnetocaloric Effect, Cryogenic, Salt Pill, Heat Switch, Instrumentation, Astronomy, Quantum Computing, Superconducting, Transition Edge Sensors, Bolometer, Kinetic Inductance Detector. Summary for Members of Congress: Ultra low temperature platforms enable cutting-edge science in astronomy, quantum computing, gamma ray spectroscopy and other research topics of national and commercial importance. A new breed of ultra-low temperature magnetic refrigerator will offer significant cost, reliability, and renewability advantages over the current use of helium dilution refrigerators.
