J-TEXT Tokamak Discharge Cleaning Effect Measurement And Research

Except for the reactant hydrogen,other particles in the tokamak are called impurities,which are divided into light impurities and heavy impurities according to the relative atomic mass.Light impurities will cause the dilution of hydrogen fuel and the increase of plasma radiation loss during the discharge process.Studies have shown that the discharge cleaning technology in the wall conditioning technology can effectively reduce the content of light impurities in the tokamak,so the use of the discharge cleaning technology plays a vital role in improving the discharge performance of the tokamak.In this paper,the J-TEXT Tokamak device is used as an experimental platform to conduct experimental research on the effect of discharge cleaning to remove impurities and the specific parameters of plasma generated by discharge cleaning.First,a differential pumping system outside the main vacuum chamber is established,which is mainly composed of a vacuum chamber,a pumping system and a measuring element.The differential pumping system is used to monitor the changes in the partial pressure of each gas in the main vacuum chamber.During the hydrogen glow discharge cleaning and Taylor discharge cleaning,the differential pumping system was used to monitor the changes in the partial pressure of each gas,thereby confirming that the discharge cleaning has a significant removal effect on light impurities.By comparison,it is found that using Taylor discharge cleaning on J-TEXT has a more obvious effect on removing impurities.During the engineering test discharge,it was detected that the impurity partial pressure and hydrogen pressure increased significantly after the discharge disruption,and the greater the plasma current and the longer the duration time before the disrupture,the more obvious the cleaning effect of the light impurity,which proved that the discharge disrupture is also effective Impurities have obvious removal effect.In addition,the discharge disrupture can remove a large amount of hydrogen adsorbed on the first wall of the device,so that the density of the plasma generated by the discharge can be easily controlled.In addition,it is verified that helium Taylor discharge cleaning can also play a role in removing hydrogen.Finally,by monitoring the partial pressure of each gas in the early morning of J-TEXT,it was confirmed from the macro that the discharge disrupture in the engineering test stage and the discharge cleaning has a good removal effect on light impurities.In addition,use the existing electrostatic probes,magnetic probes and visible light radiation diagnosis on J-TEXT to measuring plasma electron temperature,electron density,plasma current,loop voltage,carbon radiation,and hydrogen radiation for hydrogen and helium Tayor discharge cleaning.The changes of plasma parameters generated by discharge cleaning when the discharge cleaning parameters were changed were compared and the power of generating plasma was calculated.The change of the partial pressure of each gas after the discharge parameters change is measured,and the relationship between the discharge plasma parameters and the discharge cleaning effect is explored.The experiment shows that hydrogen and helium Taylor discharge cleaning have the most suitable working pressure,discharge voltage and toroidol field strength.