Research reveals the influence of different impurity gas injection on EAST divertor state and core constraint

Recently, Yang Zhongshi's research group in the Fusion Reactor Materials and Components Research Office of the Institute of Plasma Physics, Hefei Institute of Material Science, Chinese Academy of Sciences has made new progress in the radiation divertor experiment, studying the effects of different impurity gases (Ar and Ne) implantation on the divertor state and core confinement. The related research results are entitled Comparison of divertor behavior and plasma determination between argon and neon seed in EAST, which was published on Nuclear Fusion by Ph.D. student Li Kedong et al.

The high power long pulse operation of Tokamak will lead to more and more particle flow and heat flow hitting the divertor target plate, thus causing strong sputtering etching on the target plate surface, and the heat load on the target plate will exceed several times that the material/component can bear. However, impurities caused by target damage may be transported to the core, which affects the quality of fusion plasma and increases the difficulty of stable control of plasma. The most effective plasma physics scheme to reduce the sputtering and surface thermal deposition of the target plate is to properly introduce impurities at the boundary and reduce the electron temperature near the target plate surface through radiation and charge exchange. This is the operation mode of the radiation divertor that can effectively reduce the thermal load of the target plate. According to the requirements of high-parameter long-pulse operation, researchers have carried out radiation divertor experiments on EAST device for several consecutive years, and studied the effects of different inflation positions and different inflation types (Ne, Ar, D2) injection on the divertor plasma behavior and particle flow and heat flow distribution.

In a series of recent physical experiments of EAST radiation divertor, through the injection of Ar and Ne, part of the energy miss near the impact point of the upper and outer divertors was realized, and the sputtering of materials was well suppressed. However, the research shows that under the current EAST condition, whether Ar or Ne is injected from the upper outer divertor, the electron temperature near the strike point of the upper inner divertor is maintained above 10 eV, which fails to realize miss target and cannot fully protect the target surface of the upper inner divertor. In addition, when Ar implantation achieves partial energy miss, the core constraint decreases, while for Ne implantation, the core constraint increases slightly (~ 10%). The related research results provide a reference physical experimental scheme for realizing and maintaining the steady-state plasma under the condition of tungsten divertor, solving the problems of steady-state heat load and sputtering etching of target plate, and ensuring the stable operation of EAST device under the condition of high power and long pulse.


Comparison of discharge parameters between EAST # 85282 (Ar injection) and # 85291 (Ne injection)

Source: zkyzswx Voice of Chinese Academy of Sciences

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