The Study Of Real-time Temperature Monitoring Of The First Wall Components And Active Control Of Divertor Heat Flux In EAST

In EAST(Experimental Advanced Superconductive Tokamak)and future magnetic confinement fusion devices,the divertor is the region where the interaction between plasma and wall material is the most intense,and bears a large number of steady and transient heat flux in the limited and narrow region of strike point.The local high heat load results in the corrosion and melting of the target material,which affects the safe operation of the target and the device.At the same time,impurities enter the main plasma and affect the performance of the plasma.Therefore,it is necessary to develop the heat load mitigation technology of divertor,actively control the local high heat load on the target plate,reduce the impurity sputtering on the target plate,and make the target plate operate in a safe condition,which is the basis for EAST to achieve the goal of long pulse steady-state operation with higher parameters in the future.Therefore,in the long pulse high parameter plasma operation experiment,real-time monitoring of the temperature of the key components of the first wall and the development of active heat flux mitigation technology in high heat load area are of great significance to protect the safe operation of EAST device and realize long pulse discharge with higher parameters.This thesis is based on the national mega-science project EAST,which has carried out the construction and experimental research of an optical diagnostic system for monitoring and analyzing the interaction process between plasma and wall materials.By building two sets of wide angle infrared visible integrated endoscope systems on EAST,real-time monitoring,active control and analysis of the surface temperature and heat flux distribution of the first wall key areas,such as the divertor target plate and the antenna protection limiter,are carried out.The main work is as follows:Two sets of wide angle infrared-visible integrated endoscope systems were developed on EAST.The integrated endoscope system adopts a common optical path design for infrared and visible.Two sets of endoscopes monitor the first wall of the inner vacuum chamber along the tangential direction from two horizontal windows(K,G).The field of view of the endoscope can completely cover the poloidal cross section of the inner vacuum chamber,including upper tungsten copper divertor target plate,lower graphite divertor target plate,the high field side facing the neutral beam and electron cyclotron heating system,2.45GHz/4.6GHz lower hybrid wave antenna port,part of the ion cyclotron antenna and other key areas.The rear end of the endoscope is equipped with infrared band(3-5um)and visible band(0.38-0.76um)cameras,which can provide real-time plasma discharge image inside the device and surface temperature distribution data of the key components of the first wall to protect the safe operation of the device and important diagnostic data for the study of boundary and divertor physics.By using the finite element analysis software COMSOL Multiphysics,a three-dimensional heat flux calculation model of the EAST tungsten copper divertor was developed,and the two-dimensional heat flux distribution on the surface of the target was calculated by using the target temperature measured by the infrared camera.The calculation model is constructed based on the real size,structure,and material properties of the EAST tungsten copper divertor.The calculation is performed by adding the initial value,water cooling,radiation,surface temperature evolution and other fixed solution conditions.The two-dimensional heat flux distribution on the surface of the target,the peak heat load and the total energy deposited on the target with time are given by numerical calculation,and the data are compared with the heat flux data of the target given by the divertor probe,which shows a high consistency.Based on the developed infrared camera diagnosis,a real-time feedback system for the first wall temperature data was established on EAST for the first time.A new camera control and real-time data reading program was developed by using the infrared camera software development kit(SDK),at the same time,the emissivity,transmittance and environmental temperature are compensated online to obtain the surface temperature of the measured material.The obtained surface temperature of the material would be sent back to the plasma control system(PCS)in real time through the reflective memory network built,which provides the necessary conditions for the next step temperature based feedback control experiment.Based on the material surface temperature data provided by the infrared thermal imaging camera diagnosis and the developed three-dimensional thermal load calculation model of the tungsten copper divertor,the heat load characteristics of the target under the active heat load control experiment of radiation divertor are studied.The possibility of radiation feedback control experiment based on the target plate temperature is proposed.Based on the established real-time feedback system of the first wall temperature data,a new feedback control method for the radiation divertor experiment was developed.By taking the target surface temperature measured by the infrared camera as the real-time control target and controlling the divertor impurity seeding by feedback,the active control of the heat flux on the W-Cu divertor target surface based on the wall surface temperature is realized for the first time under the high confinement mode discharge in EAST.As a new type of feedback control method,the first wall material surface temperature feedback control provides a solution with good application prospects for the temperature and heat flux control of the first wall component in EAST long pulse operation.