Research on Cryogenic Technology for Phased Array Feed Receivers with Multiple Refrigerators

Similar to cryogenic receivers equipped in radio telescopes, Phased Array Feed (PAF) receivers can also achieve noise temperature improvements by refrigerating key components. This paper focuses on a cryogenic PAF receiver with a larger refrigeration capacity requirement, adopting a technical approach of full-array refrigeration and employing a cryogenic system consisting of multiple refrigerators for experimental investigation. The initial design adopted a structure where two M350 refrigerators were jointly used for refrigeration, and the measured temperature at the Low Noise Amplifier (LNA) mounting structure was only 22.3 K. Subsequently, the individual refrigeration performance of each refrigerator and the actual refrigeration power of each cold stage were tested and analyzed, and an improved partition design was proposed. In this design, the original LNAs and their mounting structure were divided into two equal parts, each independently refrigerated by one refrigerator. The improved partition design eliminated the thermal coupling and thermal back-flow in the common structure of the original joint refrigeration scheme, while halving the original thermal load and distributing it independently to each refrigerator, thereby enhancing the refrigeration efficiency of the entire cryogenic system. With this improved design, the measured temperatures of the two separated LNA mounting structures reached 15.2 K and 18.2 K, respectively, both achieving the target below 20 K. The above research systematically verifies the impact of structural differences on refrigeration performance in multi-refrigerator PAF cryogenic designs, providing a feasible approach for improving receiver noise performance, while also offering valuable guidance for the design of cryogenic systems composed of multiple refrigerators under large refrigeration capacity requirements.