The Effect Of The Plasma Irradiation On Tungsten Surface Change

There are two key factors to successful fusion energy application, especially the development of plasma facing materials: controllable thermonuclear fusion device ―Tokamak‖ and the future development of materials in a nuclear reactor. Tungsten is a rare metal material, which possesses national defense strategic significance. Its high melting point, hardness, thermal conductivity, low expansion coefficient and excellent mechanical properties, make tungsten widely used in many fields, such as national defense, aviation, photoelectric material etc. In the development process of the plasma facing materials, due to tungsten’s advantage like low sputtering rate, not reacting with plasma in fusion and low retention rate with deuterium tritium plasma, tungsten coating, block and alloy have become the most promising plasma facing material. During the service process, Tungsten, as the plasma facing material, is bearing the energetic particle bombardment continuously to protect the internal material and exclude15% fusion reaction heat. Tungsten surface damage will appear in the extreme working conditions, for example, bubble, crack, erosion and surface morphology changes. Therefore, research of plasma irradiation on tungsten has both important scientific and engineering application value in the field of fusion and far-reaching significance for the development of new energy.After design and refit the MW-ECR device, it can do long time(about 1.5×1021/m2s) and stability irradiation experiments for irradiating tungsten with a relatively large ion flux density.Investigate the influence of the material surface changing through different plasma irradiation experiments. The study found that, changing plasma ion flux density and radiation dose have influence on sputtering damage of tungsten, and changing plasma ion flux density has more outstanding effect on sputtering degree than irradiation dose. After mixing Ar/He gas with different ratio, we found that the loss thickness by sputtering is increasing gradually on the sample surface, as proportion of Ar gas increases. But once the Ar content exceeds 35%, the phenomenon disappear. Irradiate tungsten with different density of hydrogen plasma, analyze samples’ surface morphology change with different irradiation dose, and compare with deuterium plasma irradiation results in the existing references, we found that, after irradiation the surface of sample can not produce bubbles like deuterium plasma retention. Convex portion caused by irradiation will increase as radiation dose increase. After test the particle spectral line intensity of tungsten atoms, He ion, Ar ion etc in different plasma irradiation conditions by using fiber optic spectrometer, we found that, sample tungsten did not sputter at the beginning, as the irradiation dose accumulate, samples tungsten will sputter under He plasma radiation condition.Research on the damage mechanism of tungsten in plasma irradiation process, which has important and long-term significance to the further research on tungsten-based materials in fusion area, has enriched the field of low-energy and large ion flux density plasma irradiation.