Research On Measurement Technology Of Key Experimental Parameters For Steady Operation Of EAST-NBI Ion Source

Neutral beam injection(NBI)is one of the auxiliary heating methods with the the clearest heating mechanism and highest heating effect,which is widely used in plasma heating and current driving of nuclear fusion experimental devices.With the development of research on magnetic confinement nuclear fusion,the neutral beam injection system is developing towards high energy,high power and stable operation.As the core component of the neutral beam injecter,the ion source directly determines the performance of the device.The experimental parameters measurement of ion source is the most intuitive and effective mean of mastering operating state and achieving steady state operation.The research on experimental parameters measurement technology of ion source has important engineering application value for the steady state operation of EAST NBI ion source.The main research contents of this paper are shown in follows:Firstly,according to the experimental parameters characteristic of the ion source,the overall design of experimental parameter measurement system of ion source is carried out.According to the analysis of the experimental parameters of the hot cathode ion source and specific needs of physical analysis,the experimental parameters of the hot cathode ion source are defined as low-speed experimental parameters,high-speed experimental parameters,and weak signal experimental parameters.With the development of radio frequency(RF)ion source technology,the effect of RF interference on experimental parameters is solved by using band reject filter(BRF)technology.On the basis of the accurate measurement of the experimental parameters and experimental needs,the requirements of the RF power feedback control system and the cesium injection constant temperature control system are proposed.Secondly,based on the hot cathode ion source,the technical research and system development of the experimental parameters measurement system are carried out.Voltage-to-Frequency(VF)and Frequency-to-Voltage(FV)conversion technology are adopted in low-speed experimental parameters measurement system,which complete the acquisition and isolation transmission of experimental parameters.The high-speed data coding and photoelectric conversion technology are used in high-speed experimental parameters measurement system,which complete real-time acquisition and isolation transmission of high-speed analog.The weak signal experimental parameters measurement system uses the polling method to complete the signal acquisition of 16-channel thermocouples of the backstream electron dump.The system combines the serial communication protocol with the photoelectric sensor,which realizes the isolated transmission of weak signal experimental parameters.Thirdly,according to the development of RF ion source,the research on suppressing RF interference is carried out for the measurement of low-speed experimental parameters,high-speed experimental parameters and weak signal experimental parameters.The control system of RF ion source power feedback and the constant temperature control system of cesium injection are developed.In the RF discharge environment,the RF power source will cause RF interference to the experimental parameters.The experimental parameters measurement system of RF ion source is based on the hot cathode ion source,and the interference of the 1 MHz RF power source is effectively reduced by BRF.On the basis of solving the RF interference and experimental requirements,the design research of the control system of RF ion source power feedback and the constant temperature control system of RF ion source cesium injection are carried out.The control system of RF ion source power feedback realizes real-time control of the matching network,which also ensures the maximum RF incident power.The constant temperature control system of RF ion source cesium injection realizes the constant temperature control of injection environment,which supports a technical foundation for improving the negative ion yield in discharge of ion source.Finally,the measurement accuracy,frequency response,protection response time and control accuracy of the system are tested on the NBI comprehensive test bed.The test results show that the low-speed experimental parameters measurement system realizes sinusoidal test with 0-10V,3kHz.The high-speed experimental parameters measurement system realizes sinusoidal test with-10～10V,1MHz.The weak signal experimental parameters measurement system realizes 16-channel thermocouples with 25 samples per second.Experimental results show that the experimental parameters measurement systems ion source provide powerful technical support for steady state operation of NBI with high power and long pulse.