The heat flux deposition on the divertor targets with neon impurity injection on EAST has been investigated by the three-dimensional (3D) edge transport code EMC3-EIRENE. Impact of the different poloidal neon injection positions on heat flux deposition has been studied. It is found that neon impurity injected at the in-and out-board divertors (i.e. strike points) leads to the toroidally asymmetric distributions of heat load on the in-and out-board targets, respectively. However, the neon gas puffing at the upstream shows a toroidally symmetric distribution of heat load. The 3D effects of the neon radiation on the heat load have been investigated with the help of a field line tracing technique, which indicates that neon impurity injected near the strike point can radiate more power and result in a lower heat load compared with the upstream neon injection. In order to further verify the asymmetric distribution of heat load, two impurity injection locations away from the strike points at the divertor are investigated, which shows the symmetric distribution of heat load as the upstream neon injection.
The edge transport and core accumulation of tungsten (W) particles on CFETR have been studied by integrated modelling consisting of EMC3-EIRENE and STRAHL codes. The edge transport and power dissipation of W particles are simulated by EMC3-EIRENE. An in-out asymmetry of W(1-28)+ ions density has been revealed in the in- and out-board divertor regions. This is mainly due to the stronger reversal flow velocity of W ions at the outboard divertor. The upward flow of W ions near the separatrix leads to a moderate W impurity leakage from the divertor on CFETR compared to the existing full W device ASDEX Upgrade due to the high plasma density near the CFETR divertor targets. Further, the density distribution and radiation loss of W ions in the core region are investigated by STRAHL code. The high charge-state W(29-60)+ and W(61-74)+ ions mainly reside in the regions of Ψ_N = 0.20~0.98 and 0.00~0.90 (Ψ_N is the normalized poloidal magnetic flux), respectively. The W induced energy dissipation in different regions is assessed according to both STRAHL and EMC3-EIRENE simulations. Particularly, the impacts of the W core radiation on the operation regime are discussed according to the H-mode threshold scaling law proposed by Martin [Martin Y R et al 2008 J. Phys.: Conf. Ser. 123 012033] for the baseline plasma on CFETR. Further, parameter studies on the pinch velocity (v_imp) and diffusion coefficient (D_imp) have been performed to check their impacts on the operation regime of CFETR. A three-fold increase of v_imp/D_imp results in a higher W core energy loss, which can lead to the transition from H-mode back to L-mode.
Simulations of the lithium (Li) impurity transport behaviors with a liquid lithium divertor (LLD) on EAST tokamak have been performed by the fluid code EMC3-EIRENE and the Monte Carlo code ITCD. The interactions between particles and wall surface like the gyration-induced scrape-off effect, sheath acceleration, kinetic self-sputtering and reflection are typically ignored or simplified in fluid models. In order to uncover the impacts of the scrape-off effect, sheath acceleration, kinetic self-sputtering and reflection on Li distribution, the detailed analysis of the density distributions of Li1+ and Li2+ ions at the divertor region have been carried out by ITCD modelling. The newly-upgraded ITCD code can principally reproduce the distribution patterns of Li ions as well as EMC3-EIRENE under the identical plasma conditions on EAST. While, due to the scrape-off effect and sheath acceleration, the densities of Li1+ and Li2+ ions simulated by ITCD are evidently reduced compared to the EMC3-EIRENE simulations. The kinetic self-sputtering by redeposited Li particles in ITCD can increase the Li ions densities. Moreover, the kinetic reflection database calculated by SRIM code has been employed by ITCD, which leads to an increase in the Li densities compared to the reflection approach used in EMC3-EIRENE. Overall, by adding the aforesaid physical effects in ITCD, the total Li ions number shows an obvious reduction compared to the EMC3-EIRENE modelling.
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