The Construction Of EAST Radiative Divertor Feedback Control System And Experimental Study Of The Radiative Feedback Control

The divertor is one of the essential components on tokamak devices,which is used to exclude and shield the impurity particles during the plasma discharge.Also,to protect the other plasma facing components,the divertor target plates will sustain the excessive heat power.The sputtered impurity particles from the damaged divertor will contaminate the plasma,degrade the confinement quality and fusion efficiency.With the increment of the input power and the upgrade of the plasma parameters,the power load on the divertor will be far beyond than the material tolerance.Thus,the divertor heat load has been one of the most challengeable issues for the ITER project and the fusion reactors.It is necessary to develop the control technique to reduce the power flux on the divertor,which is of benefit to extend the device lifetime and mitigate the discharge environment.The divertor heat flux is determined by the edge plasma,especially by the scrape-off layer(SOL).The "two-point" model is a typical description of the particle and power transport between the divertor surface,SOL and the main plasma,and it provides two ways to optimize the divertor heat flux:1.Lifting the power exhaust of the volumetric radiation process by additional impurity seeding;2.Generating the stable detachment or partial detachment plasma by high edge radiation power loss or high upstream plasma density.The one of the main purposes of this thesis is building the radiative divertor feedback control system to realize the active control of the plasma radiation power and detached phase.The multiple algorithms are developed in the EAST plasma control system(PCS).The real-time target value is calculated by the diagnostic data from the radiative measurement,divertor probe and the infrared camera system.The actuator are several kinds of the EAST gas puffing system.The joint control function of the electrical temperature and radiated power is also set up.The radiative feedback control has been implemented in the both L-mode and H-mode EAST discharges.Injecting different kinds of the impurity gas,the total radiated power was stably controlled in the continuous adjustment experiments of the radiated power.The experimental results suggest that,in the reasonable control range,the radiation fraction is high enough to optimize the divertor heat load,while the plasma confinement has no obvious degradation.The control methods of the divertor temperature and particle flux are also implemented in the experiments to achieve the controllable plasma detachment.The CD4 is firstly used in the Te,div control system to lower the divertor electrical temperature at 5eV.The two control methods of the saturation ion current are also realized in the actual experiments.The control algorithm can precisely judge the roll-over process to make the plasma into the partial detach phase by lifting the upstream plasma density.The feedback control of the divertor target surface temperature was also implemented successfully in the H-mode discharge.The joint Te div-Prad feedback control are realized in both the total and the single-chord radiated power mode.Using less impurity seeding amount,the high-performance plasma is into detachment phase,and the stabilization of the control system is also improved.EAST radiative feedback control system provides a stable control stage to the research of the EAST radiative divertor.The upgrade of the control system and the relative physical issues in the feedback control experiments will be studied further in the future.