Research On Optimization Of Arc Discharge Control System For Neutral Beam Injection High Current Ion Source

Neutral beam injection(NBI)heating is one of the most effective heating methods for tokamak devices.Large and medium-sized tokamak devices at home and abroad are equipped with complete NBI heating beams,and have achieved remarkable results.Arc power supply is one of the important parts of the NBI power system,and its performance seriously affects the efficiency and stability of NBI.The HL-2M device has undergone a major upgrade and transformation on the HL-2A device.Among them,the NBI arc power supply is improved from the thyristor phase-controlled voltage regulation technology to the super capacitor-based switching power supply technology,which greatly improves the performance of the arc current power supply.At present,the NBI arc power supply of the HL-2M device is undergoing debugging experiments on the ion source test platform,and the experimental results have been improved compared with the HL-2A device.However,due to the particularity of the load,the current ripple needs to be optimized to ensure that the beam is drawn normally.Therefore,the influence of the sampling frequency of the control system on the stability of arc discharge is studied.At the same time,in order to solve the accelerator load problem and realize long pulse injection,the central control system was optimized and transformed,and an experimental scheme of high and low power alternating pulse injection was proposed.This paper uses the NBI ion source test platform to carry out related experimental research,compares and analyzes the NBI arc current power supply of the HL-2A device and the NBI arc current power supply of the HL-2M device.By establishing the mathematical model of the control system of the arc current power supply of the two devices,we can calculate the system transfer function.Meanwhile,we use MATLAB to simulate the step response performance of the arc current power supply of the two devices,compare and analyze the performance of the arc current power supply of the two devices,and simulate and analyze the influence of sampling frequency on NBI arc current power supply of HL-2M device.Then,an arc discharge experiment was performed on the NBI ion source test platform to verify the simulation results.The arc discharge experiment at different sampling frequencies was completed on the NBI test platform.The experimental test obtained the effect of the sampling frequency on the arc discharge stability,which was consistent with the simulation results.The optimal sampling frequency for stable arc discharge on the NBI ion source experimental platform was determined.The arc discharge experiment was completed on the HL-2A device,and the experimental test results were consistent with the simulation.The influence of the arc current power supply on the stability of the arc discharge was determined,which laid the foundation for the optimization of the arc current power supply.In order to achieve long pulse injection,a scheme of high and low power alternating pulse injection is proposed.Optimize the central control system of the NBI ion source test platform to realize the alternating operation of arc current power supply and high-voltage power supply.The arc discharge experiment was completed on the NBI ion source test platform,which proved that the scheme was feasible.However,arc discharge is unstable at low parameters,which is not conducive to beam extraction.Therefore,the reasons for the unstable arc discharge under low parameters are analyzed and the relationship between the filament voltage and the arc current during stable arc discharge is matched,which provides a basis for the parameter settings of the filament power supply and the arc current power supply in the future experiments.