Magnetic Shield Design and Simulation Optimization of Metallic Magnetic Calorimeter in Ultra-Low Temperature Working State

Metallic magnetic calorimeters (MMC) are low-temperature particle detectors based on calorimetry. They typically operate at temperatures below 100 mK. They utilize a metallic paramagnetic temperature sensor to convert the temperature rise of an absorber, during the absorption of energetic particles, into a change in magnetic flux sensed by a superconducting quantum interference device (SQUID). Since the SQUID has a high sensitivity to magnetic signals, the MMC system is very sensitive to external magnetic field interference. The magnetic shielding effect of the MMC directly affects its detection capability. Therefore, the design of the MMC magnetic shield system is particularly important. In this study, a set of MMC magnetic shields is designed based on the principle of magnetic shielding. The design is optimized using the COMSOL magnetic field simulation module by varying relevant parameters, such as the thickness and height of the shields as well as the diameter of the radioactive source hole, which determines the magnetic shielding effect. Through the simulation, the optimized magnetic shielding device can reduce the magnetic field interference of 2–0.0264 nT. The value can be further reduced by one order of magnitude if a high-permeability material with superior performance is used. This research is instructive for the design of MMC magnetic shielding devices in subsequent experiments.