9T Conduction-cooled Superconducting Magnets Design Of Physical Quantity Monitoring System

Since the discovery of superconductivity at the beginning of the last century,the research on the application of superconducting materials has never stopped,and superconducting magnet systems are one of the major applications of superconductivity technology.After more than a century of technological development,superconducting magnets are widely used in many applications such as biomedicine,laboratory research,superconducting energy storage systems and particle accelerator.Among the cooling methods of superconducting magnets,direct cooling by cryo-cooled occupies a major position in the future development of superconducting magnets because of its small size,compact structure and simple operation.This paper is aim to design a physical measurement system for 9T conductioncooled superconducting magnets,covering parameters such as temperature,stressstrain,voltage,and magnetic field strength.The main studies and results are as follows:(1)A low temperature thermometer Cernox-1030 and a carbon resistance thermometer are used for temperature measurement in the liquid helium temperature region,and PT100 thermometers are used in the liquid nitrogen temperature region for temperature acquisition in the full temperature region(3～300K).The OSP-A fiber optic grating strain gauge without temperature compensation and its accompanying fiber optic demodulator were used for the stress-strain measurement,and the reliability of the strain measurement system was verified through comparative experiments;(2)Build the hardware and software of the acquisition system using Lab VIEW development software and NI Compact RIO controller,NI 9209 voltage acquisition board and NI 9216 platinum resistance acquisition board.The data acquisition program can achieve the following functions: the acquisition frequency can be adjusted,the number of sampling points can be selected,the sampling channel can be selected,and the table look-up of voltage to temperature values can be achieved through sub-VI;(3)For the calibration needs of cryogenic thermometers,we independently develop a full temperature range cryogenic thermometer calibration device based on the liquid helium-free test system.A Cernox-1030 thermometer was used as the iii standard thermometer to calibrate the carbon resistance thermometer.The results show that the calibration system can realize the calibration function of cryogenic thermometers in the full range of 3—300K,and can be programmed to calibrate specific temperature zones at specified temperature intervals automatically.Based on the high integration of the cryogenic system and the data acquisition system,the calibration uncertainty is quantified and the calibration error of the calibration system in the temperature range of 3—7K is ± 8.38 m K.The ultimate goal of the research is that the measurement system will be stable,accurate and timely provide useful data to the magnet developer,be intelligent,intuitive and simple to operate,allow the user to quickly obtain the measurement data they needed to analyze the magnet’s operation.