Evaluation of edge transport and core accumulation of tungsten for CFETR with EMC3-EIRENE and STRAHL

The edge transport and core accumulation of tungsten (W) particles on China Fusion Engineering Test Reactor (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 psi(N) = 0.20-0.98 and 0.00-0.90 (psi(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 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.