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Description
The divertor is one of the most crucial components of a tokamak device, serving two primary functions: heat exhaust and helium ash removal. In future fusion reactors, the parallel power flux entering the divertor is expected to exceed 1 GW/m². The divertor is expected to experience extremely high thermal loads in future fusion reactors. Therefore, the development of an advanced divertor is essential to reduce the heat load on the divertor targets. Extensive experimental studies have demonstrated that the snowflake divertor (SF-) can effectively reduce the target heat flux. This reduction can be attributed mainly to two mechanisms: (1) The extremely weak poloidal magnetic field near the second X-point decreases the projection angle between the magnetic field lines and the divertor targets, and (2) The SF- spreads the incident particle flux over a larger area, increasing the plasma–divertor contact surface.
The HL-3 tokamak is capable of flexibly realizing multiple snowflake configurations, including snowflake-plus (SF+) and snowflake-minus (SF−) [1]. Experiments have verified that the SF- effectively disperses the particle flux and reduces the local heat load on the divertor targets. However, HL-3 experimental results also showed that although the open SF-divertor provides strong flux spreading, it exhibits relatively weak particle recycling and low neutral pressure, which are unfavorable for achieving both detachment and effective pumping [2]. Thus, in this work, based on HL-3 SF- experiments, we employed SOLPS-ITER simulations to investigate the physics of the open SF-divertor. The main topics include [3]: (a) the mechanism of target particle flux double peaks and particle flux spreading, and (b) the impact of drifts on particle transport and detachment behavior for SF-. This work provides a solid theoretical foundation for the application of the SF- divertor in future reactors.