Main technical parameters of the system:

1. Cooling capacity: primary cooling 40W@45K Two stage refrigeration 1 0W@4.2K The power required is 380V, 50 Hz.

2. Working pressure: < 2 × 10-4Pa； During normal production, the leak will be detected by helium mass spectrometer leak detector, and the vacuum degree can reach 10-5pa, depending on the limit vacuum of the pump. T-station 85 molecular pump group produced by Edward is selected for this vacuum pump, and the limiting vacuum of the molecular pump is 10-6pa.

3. Temperature monitoring: a temperature measuring point is set at the sample table to monitor and display the temperature of the sample. Temperature measurement accuracy ± 0.01K.

4. The cooling and heating time of the sample: the cooling time to 4.2K is less than 2h, and the time to return to normal temperature in vacuum is less than 3h after the refrigeration is shut down. The device is cooled by a closed cycle refrigerator without liquid helium, and the refrigeration capacity is 4.5K 2K@1.0W The cooling time from no load to 4.2K is 30min. When the load is installed, considering the cooling of the load and related supporting devices, the cooling system is designed.The cooling time will be prolonged correspondingly, but according to experience, the cooling time is about 50 minutes, which meets the experimental requirements.

5. Integrated control system: control vacuum system, refrigerator operation and safety feedback function. It can set and display working target parameters and system working status, and has feedback safety control function.