This Small Business Innovation Research (SBIR) Phase I project will demonstrate the feasibility of a novel Continuous Adiabatic Demagnetization Refrigerator (CADR) design by building and testing a prototype. This new technology has the potential to greatly reduce the cost of ultra-low temperature research. Currently, if a researcher needs to keep an experiment below 0.1K for more than a few days, there is only one viable technology: Dilution Refrigerators. These refrigerators rely on the very rare isotope He-3 (largely sourced from Tritium decay within the nuclear stockpile) and are quite expensive ($350,000 or more). The technology to be developed in Phase I promises to reduce this cost significantly by avoiding the complexity, size, infrastructure requirements, and He-3 reliance of Dilution Refrigerators. The envisioned CADR has the potential to help enable cost-effective quantum computing, the wide deployment of hyper-sensitive detectors for tracking nuclear material, the creation of quantum-information sensors critical to certain cryptographic schemes, in addition to other outcomes heretofore unknown.
The intellectual merit of this project is the creation of a revolutionary ultra-low temperature refrigerator. During this Phase I effort, a prototype refrigerator will be created which demonstrates the basic working principles of this new design. This prototype refrigerator will operate using a single stage of Gadolinium Gallium Garnet (GGG) as a refrigerant for continuously lifting heat from sub-Kelvin temperatures to a 3K pulse tube. This refrigerator will serve as a proof-of-concept for a two-stage refrigerator to be designed and tested in Phase II. The future two-stage refrigerator will use GGG to precool ferric ammonium alum (FAA) in order to reach 0.1 Kelvin and below. The research in this Phase I effort will feature an iterative process of subsystem characterization (heat switches, magnetic shielding, etc.), design, build and test. The Phase I effort is focused on answering the feasibility questions surrounding the engineering of this CADR while leaving 100 mK temperatures, multi-stage cooling, and deep analysis to Phase II. A successful proof of concept refrigerator to be demonstrated and characterized at the end of Phase I will move useful heat (goal of 0.5 milliwatts) from sub-Kelvin temperatures to a 3K pulse tube.
