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在中国聚变工程实验堆(China Fusion Engineering Test Reactor,CFETR)的工程概念设计中,为探索有效降低偏滤器靶板热负荷的途径,相对于国际热核聚变实验堆(International Thermonuclear Experimental Reactor,ITER)特别增加了两个极向场线圈用于产生近年来新提出的雪花偏滤器位形。脱靶运行状态下,偏滤器靶板上的热负荷显著降低,但同时由于偏滤器温度的降低,杂质约束性能会变差,因此需要对CFETR雪花偏滤器的脱靶运行状态进行研究。基于边界等离子体物理模拟软件SOLPS(Scrape-off Layer Plasma Simulation),通过数值模拟研究了CFETR雪花偏滤器的脱靶运行状态。模拟中通过主等离子体室内的D2充气改变等离子体密度。当充气速度足够高时,CFETR雪花偏滤器实现完全脱靶,靶板上的离子流和热负荷都显著降低。但此时偏滤器区域等离子体温度已经非常低,杂质将容易通过X点进入芯部,有产生辐射不稳定性的风险。因此,对于CFETR雪花偏滤器较为合适的工作状态应当是部分脱靶运行。
In the conceptual design of China Fusion Engineering Test Reactor (CFETR), in order to explore ways to effectively reduce the heat load on the divertor target plate, compared with the International Thermonuclear Experimental Reactor (ITER) In particular, two polar field coils have been added to create the newly proposed snowflake divertor configuration. In off-target operation, the heat load on the divertor target plate is significantly reduced, but at the same time the impurity restraint performance is deteriorated due to the decrease of divertor temperature. Therefore, the off-target operation of CFETR snowflake divertor should be studied. Based on the boundary-layer plasma physics simulation software SOLPS (Scrape-off Layer Plasma Simulation), the off-target operation of CFETR snowflake divertor was studied by numerical simulation. In the simulation, the plasma density is changed by inflating D2 in the main plasma chamber. When the inflation rate is high enough, the CFETR snowflake divertor achieves a complete off-target, with a significant reduction in ion flux and heat load on the target. However, at this time, the plasma temperature in the divertor zone is already very low and impurities will easily enter the core through point X with the risk of radiation instability. Therefore, a more suitable working condition for the CFETR snowflake divertor should be a partial off-target operation.