Research On New Quench Detection Method Based On Radio Frequency Wave Technology

Magnetic confinement fusion is the most probable method of controlled nuclear fusion at present.This method mainly uses a magnetic field to constrain the plasma to cause controlled nuclear fusion under a sufficiently high temperature environment.Superconducting magnets store huge amounts of energy when operated at heavy current.The huge energy stored will be quickly converted into heat,which will cause great harm to superconducting magnets and device when quench.Therefore,quench detection is critical in the operation of large superconducting Tokamak devices.The research content of this paper is the new type of quench detection method proposed in the world for the first time-a new quench detection method based on radio frequency wave technology.During the propagation of radio frequency waves,changes in impedance cause changes in reflectivity.Once the superconductor is quenched somewhere,the reflectivity there will change.It is determined whether the reflectance changes by detecting the received radio frequency wave,thereby judging whether or not the quench is exceeded.The biggest advantage of the RF wave quench detection method is that it does not require the installation of sensors or leads inside the test object,and it has a faster response speed than other backup detection methods.According to the characteristic of radio frequency wave,the possibility of applying radio frequency wave technology to quench detection is proposed.Then,the influence of the resistance change of the test object on the reflectivity is calculated by the theory of radio frequency wave transmission line,and the influence of the characteristic impedance of the transmission line on the system performance is analyzed.The analysis shows that the RF wave quench detection method is theoretically completely feasible.According to the principle of radio frequency,the RF wave quench detection system is designed into the following main components:power source,ring isolator,balun and receiver.According to the requirements of quench detection,the performance indicators of each component are proposed.The RF wave quench detection system completed the overload quench detection,the thermal trigger quench detection and the 0 current quench detection.The feasibility of the detection method is proved by comparison with voltage detection.The quench detection can be performed during the change of the superconductor from zero resistance to several tens of micro ohms.And found some shortcomings to provide experience for the next step of improvement.At present,verification experiments on small coils of high temperature superconducting coil have been completed,and it is hoped that relevant verification experiments will be carried out on low temperature superconducting coils and large superconducting coils in the future.The radio frequency wave quench detection method is the first international exploration of the application of radio frequency wave technology to quench detection.The experiments prove that the radio frequency wave quench detection method is qualified for the backup quench detection method of large Tokamak devices in the future,and is an effective supplement to the existing quench detection methods.