Study on formation mechanism of dust particles in divertor plasma simulators

在NAGDIS-II型线性偏滤器等离子体模拟器上，研究了高密度氢等离子体和氢/氦混合等离子体辐照下石墨表面碳尘粒子的形成。碳尘颗粒产生在面对高密度等离子体的石墨表面的中心区域。在外围区域中没有形成粉尘颗粒。这些观察结果表明，由于等离子体柱中心的强等离子体流，碳氢离子的再沉积过程是决定尘埃生长和化学溅射的关键因素之一。低能量和高通量的等离子体暴露在钨表面会导致气泡/孔洞的形成。随后在2,000K下，氦等离子体在水泡表面形成孔洞结构，包括水泡表面，一些水泡由于再结晶和水泡皮肤上气泡的形成而坍塌。在550K的氦等离子体辐照后，在1600K的预曝光形成空穴结构的W表面上观察到了颗粒抛射。

Formation of carbon dust particles on a graphite surface irradiated by a high-density hydrogen plasma and a mixed hydrogen/helium plasma has been investigated in the NAGDIS-II linear divertor plasma simulator. Carbon dust particles are generated at the center region of the graphite surface facing the high-density plasma. No dust particles are formed in the peripheral region. These observations indicate that the re-deposition process of the hydrocarbon ions due to a strong plasma flow at the center of the plasma column is one of the key factors determining the dust growth as well as chemical sputtering.Low-energy and high-flux plasma exposures on tungsten surfaces result in blister/hole formation. Subsequent He plasma exposure at 2,000 K on the blister-rich surface forms a hole structure on the surface, including the blister surface, and some blisters collapse due to recrystallization and bubble formation on the blister skin. Grain ejections were observed after deuterium plasma exposure at 550 K on a W surface on which a hole structure had formed due to He pre-exposure at 1,600 K.