Design and Test Analysis of Thermometer Calibration Platform for 1.8 K to 300 K

The precise measurement of temperature is crucial for nuclear fusion devices operating in ultra-low temperature magnetic field environments. The accurate temperature measurement and calibration in ultra-low temperature environment has a direct impact on the development of nuclear fusion, high energy physics, aerospace and other research fields involving ultra-low temperature environment. Relying on the comprehensive research facility CRAFT for fusion reactor host systems, a liquid helium temperature calibration platform has been designed to carry out temperature calibration and experimental research in the temperature range of 1.8 K to 300 K. The platform uses the Gifford-McMahon Cycle Chiller （GM Chiller） and capillary throttling refrigeration to cool the sample chamber to 1.8 K. By controlling the temperature of the sample chamber by adjusting the heater power, the temperature environment of ±5 mK fluctuation in the temperature zone of 1.8 K to 20 K and ±15 mK fluctuation in the temperature zone of 20 K to 300 K can be achieved. Low-temperature measurement and control equipment are used for temperature control and data acquisition at different temperature points in the calibration area, resulting in a calibration accuracy of ±4.39 mK at 1.8 K to 4.2 K, ±6.08 mK at 4.2 K to 20 K, and ±75.62 mK at 20 K to 300 K.