Experimental study of the influence of gas puff locations on H-mode boundary plasmas with argon seeding on EAST

To investigate the optimal scenario of impurity seeding to obtain divertor plasma detachment for target protection, experiments with Ar&D2 seeding from two different poloidal locations, the upper outer (UO) divertor target and lower outer (LO) target, were carried out on EAST. Partial energy detachment (the electron temperature near the strike point Te,spt ≤10 eV) were obtained with Ar&D2 mixture puffing from the UO target and, for the first time, from the LO target into H-mode plasmas in the upper single null (USN) configuration. The peak heat flux qt on the UO target was significantly reduced (by ~80%). The rollover of ion flux density js did not appear probably due to insufficient momentum loss, which is independent of the puff locations. The poloidal asymmetries of particle and heat fluxes on the targets have also been investigated. The UO-dominant asymmetry of particle flux was reversed, while the UO-dominant asymmetry of heat flux was mitigated but not reversed. The plasma confinement dropped by only 14% and 8.2% in the LO-puff case and UO-puff case, respectively, during detachment. The high level of C may contributed greatly to the higher radiation in the bulk plasma region and the greater decline in WMHD in the LO-puff case.

为探究实现偏滤器等离子体脱靶以保护靶板的最优杂质注入方案，本研究在东方超环（EAST）上开展了实验，分别从极向两个不同位置——上外侧（UO）偏滤器靶板与下外侧（LO）靶板——喷注氩气（Ar）与氘气（D₂）。在采用上单零位形（USN）的高约束模（H-mode）等离子体中，通过从UO靶板喷注Ar与D₂混合气实现了部分能量脱靶（打击点附近电子温度T_e,spt ≤10 eV），且首次在从LO靶板喷注的工况下达成该条件。UO靶板上的峰值热流q_t显著降低约80%。离子流密度j_s未出现滚降现象，该现象大概率源于动量损失不足，且与喷注位置无关。本研究同时对靶板上粒子流与热流的极向不对称性展开了探究：原本以UO侧为主导的粒子流不对称性发生反转，而以UO侧为主导的热流不对称性虽得到缓解，但并未发生反转。在脱靶过程中，LO喷注工况与UO喷注工况下的等离子体约束性能分别仅下降14%与8.2%。LO喷注工况下，等离子体主体区域的辐射水平更高，加权磁流体动力学（WMHD）能量约束的降幅也更大，这一现象大概率与高浓度碳杂质密切相关。