DMRadio-50L: Cryogenic Design

In order to effectively search for the axion, the DMRadio-50L experiment is cooled to sub-Kelvin temperatures, thus minimizing thermal noise and increasing sensitivity. A variety of stable temperatures are required for operation: 4K for the magnet, <1K for superconducting shields, and 20mK for high-Q resonant components. To achieve these different temperatures within a large bottom-supported cryostat, various cryogenic engineering solutions were employed including the development of a cold-snout to deliver ultra-cold temperatures to the center of the detector. I will discuss the unique constraints of connecting a bottom-supported cryostat with a horizontal dilution refrigerator by the cold-snout, the design of which requires a balance of the different heat load demands, light leaks, and various mechanical compliances. I will also touch upon the expected heat loads on different temperature stages of the experiment and the thermal gradients associated with them as well as present results from preliminary thermal tests of the cryogenic system intended for use in the experiment.