Design And Implementation Of Data Acquisition System For Superconducting Magnet

In 1911,Onnes discovered the superconductivity of mercury below 4.2K,which opened the door to the world of superconductivity.In 1933 Meissner and Ochsenfeld discovered that superconductors were perfectly diamagnetism;In 1954,the National Bureau of Standards created the first permanently stable superconducting magnet;In 1961,the Massachusetts Institute of Technology produced the first large superconducting magnet cooled by liquid helium.Since then,the technology of making superconducting magnet by using superconductivity phenomenon has developed rapidly.Thanks to the same volume of superconducting magnets can produce a very strong magnetic field,it has created the bright pearl of science Island-particle accelerator.The Institute of Modern Physics of the Chinese Academy of Sciences undertook the construction of two major scientific facilities in the Twelfth Five-Year Plan period,which were listed in the Medium and Long-term Plan for the Construction of National Major Scientific and Technological Infrastructure(2012-2030).They are High Intensity heavy-ion Accelerator Facility(HIAF)and China initiative Accelerator Driven System,respectively.CiADS).Both HIAF and CiADS contain superconducting beam wires made up of multiple superconducting magnets.In the process of realizing the high stability magnetic field,not only the stability of the output excitation current of the magnet power supply is required to be high,but also the acquisition accuracy of the magnetic field value is also required.At the same time,the superconducting magnet is interfered by external factors during its operation to generate loss and timeout.In order to avoid magnet damage,the protection system needs to cut off the excitation current quickly.Obviously,the faster the monitoring of the loss signal and the triggering of the protection action,the better.To sum up,high precision and real-time data acquisition of superconducting magnet is particularly important.At present,the data acquisition system based on cRIO series products is relatively complete in function and stable in operation,which can meet the requirements of magnetic field measurement and quench detection.However,as it is a commercial product,it is difficult to upgrade by itself,and the supply and after-sales cycle is long.Besides,the price of cRIO and I/O module is high,which is not conducive to largescale distributed field deployment.Therefore,it is very necessary to develop a new data acquisition system for superconducting magnets that meets the performance requirements and costs less.In this paper,based on ZYNQ-7045 and high precision ADC,a data acquisition system of superconducting magnet is designed.Meanwhile,its software is developed,which can realize data acquisition,fault detection,machine protection and other functions.The EtherCAT protocol can be used for networking and distributed deployment.The data acquisition system consists of ZYNQ digital processing board and ADC acquisition sub-board.The former is responsible for digital signal filtering,algorithm processing,logic judgment,also responsible for communication with the upper computer or EtherCAT master station;The latter is responsible for filtering the acquired signal and AD conversion.In addition,aiming at the application scenarios of high-precision real-time magnetic field measurement,this paper proposes a magnetic field measurement scheme based on multi-sensor fusion,and carries out actual measurement verification on the two-stage magnet.The results show that after multi-sensor fusion,the influence of noise is reduced and the measurement accuracy is improved.The software and hardware tests of the superconducting magnet data acquisition system show that the dynamic performance of AD conversion is good,the noise level is low,the channel is not easy to be affected by cross talk,the effective resolution number is up to 14 bits,the short-circuit noise is less than 3.5mV,and the error is less than 0.69%,which can meet the requirements of data acquisition.Its communication interface works properly and can communicate with upper computer and EtherCAT master station.