Study And Design Of An Improved Electron Drift Injection System On The J-TEXT Tokamak

The electron drift injection method injects electrons into tokamak by electric drift,So it's a simple method to realize low loop voltage start-up.Besides,this metod may accumulate extra negative charge which generates a radial electric field,thereby improving the plasma confinement.Some experiments about electron drift injection had been made in the J-TEXT tokamak,but some problems exist in the existing electron drift injection system,such as few emission electron,low electron's initial energy,complex transmission system in operation,low mobile accuracy,low insulation,unbalanced power supply and insufficient power,and all of them have a serious impact on electron drift injection.Therefore,in this paper,an improved electron drift injection system assisted with electron gun on J-TEXT tokamak is proposed and designed.According to the electron drift injection's basic principle,mathematical models on injected electrons' trajectories are built,and the relevant values of electron drift injection are calculated,and electrons' trajectories under the different conditions are simulated and analysed with a software.And simulation results show that the proposed design scheme is feasible.Thereforce,in order to improve the number of injected electrons,electrons' initial energy,an electron gun is designed;With the purpose of protecting magnetic field from the influence of the toroidal magnetic field,a magnetic shielding device is designed;Transmission system is designed to be a remote operation one driven by a stepping motor have an easier operation system about it and higher moving precision;An improved design is made for it so that the outgassing rate of the wire and improve its insulation can be reduced;In order to solve the problems including low output voltage and low output power of the existing bias voltage power supply,the voltage power supplies system is upgraded,and with LABVIEW software,the remote control interface of power supply system is designed.After the improvement of the electronic drift injection system,the heat test and simulation experiment on the electronic gun,the toroidal magnetic field test on the magnetic shielding device of the electronic gun are carried out,the test reults can meet design requirements;Transmission system is debugged,the results show its error is about 0.01 mm,which meets design requirements;the outgassing rate test and insulation test are made,the test results show that its outgassing rate is low and withstand 10 kV voltage without breakdown;The bias power supply is simulated and tested,the simulation results and experimental results meet the design requirements.Finally,the remote control interface of the designed power supplies system is debugged,and after debugging,it can achieve remote-control of the power supplies system in the control room.