| Fusion energy is one of the most promising ways to solve the problem of energy in the future, and magnetic confinement fusion is one of the key issues in the study of fusion energy. People have developed a lot of magnetic confinement fusion devices researching for above half a century, in which Tokamak is considered to be one of the most potential device, and a large number of experimental devices have been built around the world. ITER plan’s establishing marks a milestone for magnetic confinement fusion research. Subsequently, Tokamak research is based on ITER as the goal to start. Together with DEMO, ITER undertakes the task of Tokamak research in the next few decades.EAST is the first full superconducting tokamak in the world, and it is one of the signs of fusion energy research in China. Since the device was built and put into operation in 2006, it has experienced many times of transformation and upgrading, and also achieved a lot of breakthrough in the plasma performance. For EAST, the surface area of vacuum chamber is about 60m2, while the plasma volume is about 48m3. On EAST, the first wall is molybdenum tile, and the filter is made of tungsten and copper material. A variety of wall processing technology is taken on EAST, such as baking, GDC, ICRF, and silicon or lithium for coating.In this paper, the influence of the wall treatment technology on the wall condition and the performance of the plasma was analyzed based on EAST experiments. Conclusions are as follows:(1) Baking is mainly effected by the baking temperature and baking time. Baking leads the high-temperature desorption of impurities in the wall, so the removal effect of adsorption with low energy bond and high Z organic impurity results good. Vacuum conditions have improved after a long time baking, but still cannot meet the needs of high performance plasma discharge.(2) Discharge cleaning. Due to particles of high energy impacting the wall surface, impurities with high energy bond can be removed. Discharge cleaning is helpful for the removal of impurities and the establishment of the plasma. The effect of discharge cleaning is different from that of the working gas.th or D2 discharge cleaning involves chemical reactions, so the removal effect is better than He discharge cleaning, while the latter can remove H2. However, H2 removal efficiency of D2 discharge cleaning is still better than that of He.The difference between GDC and ICRF discharge cleaning is also very significant. GDC cleaning effect is more uniform. But GDC can’t carry out in magnetic field, which differs from ICRF discharge cleaning. As auxiliary technology for coating, ICRF discharge cleaning is better than GDC.(3) Boronization, siliconization, and lithiation can greatly decrease the level of impurities, increase the plasma density and improve fuel recycling. Due to the excellent characteristics of lithium, ITER takes special attention to the lithiation. Lithium can also have a protective effect on the wall of the device under the discharge disruption.In addition, the disruption can be used as a strong wall treatment measure as well. Wall treatment technology can improve the wall conditions, which is conducive to the realization of the next plasma discharge, and greatly improve the performance of the plasma. The treatment of hydrogen isotope retention problems is also helpful to solve the problem of safety due to tritium retention in the future device. These studies can provide a reference to reduce the wall impurities and retention for the high parameter plasma operation as well as the effect of parameters on composition analysis in the Future. |
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