This paper provides an investigation of the production/transport properties of W impurity in the edge of experimental advanced superconducting tokamak (EAST) H-mode discharges with upper-single-null configurations by using DIVIMP Monte-Carlo code. The background plasmas are provided by SOLPS5.0 calculations. Firstly, to address the detailed dependence of W impurity behaviors on plasma conditions in the scraped-off layer (SOL)/divertor region of EAST, two pre-edge localized mode (ELM) cases with divertor plasmas in high-recycling and partially-detached regimes, respectively, are considered and compared. It is found that, due to the competitions between the thermal and friction forces (FFs), in the high-recycling case, large quantities of W impurities are transported to the upstream; while in the partially-detached case, most of the W impurities are located near the inner and outer divertors. Furthermore, the W core contamination in type-I ELMy H-mode plasmas of EAST has been estimated by the DIVIMP-SOLPS5.0 simulations, without the consideration of the release of W impurity from the core due to ELMs. During the ELM, simulations exhibit the low-recycling regime of divertor plasma, and high (several hundred eV) target plasma temperatures together with low SOL collisionality ( ∼ 1–3), lead to an order of magnitude increase in the W core contamination rate. However, in the ELM-recovering phase, with the decrease (increase) of divertor plasma temperature (density), significant increase of divertor retention is obtained due to the remarkable increase of FFs on W ions. Besides, intra-ELM phase approximately contributes to more than 50% of the total W core contamination per an ELM cycle. This work represents a step toward a deeper understanding of the W impurity production/transport in EAST H-mode discharges.
本论文利用DIVIMP蒙特卡洛代码，对实验先进超导托卡马克（EAST）H模放电中上单零位形下边缘区域W杂质的产生/输运特性进行了研究。背景等离子体由SOLPS5计算提供。首先，针对EAST刮削层（SOL）/偏滤器区域中W杂质行为对等离子体条件的详细依赖性，分别考虑了高再循环和部分脱离两种偏滤器等离子体状态下的两个预边缘局域模（ELM）案例，并进行了比较。研究发现，由于热力与摩擦力（FFs）之间的竞争，在高再循环案例中，大量W杂质被输运到上游；而在部分脱离案例中，大部分W杂质则位于内、外偏滤器附近。此外，通过DIVIMP-SOLPS5模拟，在不考虑ELM引起的W杂质释放的情况下，估算了EAST I型ELMy H模等离子体中的W芯部污染。在ELM期间，模拟显示出偏滤器等离子体处于低再循环状态，靶板等离子体温度较高（数百电子伏特），且刮削层碰撞率较低（约1–3），这导致W芯部污染水平增加约一个数量级。然而，在ELM恢复阶段，随着偏滤器等离子体温度（密度）的降低（升高），由于W离子所受摩擦力的显著增强，偏滤器对W的滞留能力明显提高。此外，ELM内阶段对单个ELM周期内W芯部总污染的贡献约超过50%。这项工作为深入理解EAST H模放电中W杂质的产生/输运机制迈出了重要一步。