Simulation study of the influence on the tungsten concentration due to the cross-field transport in the scrape-off layer.

It is critical to keep a low level of tungsten impurity concentration in the core plasma of the fusion reactor. Using the OEDGE code, the influence on the tungsten concentration due to the cross-field transport in the scrape-off layer is studied. Based on the design parameters of the China Fusion Engineering Test Reactor, the background plasma with the peak target electron temperature of 15 eV is generated using the onion-skin model. The neon impurity with the assumed concentration of 0.2% inside the separatrix is included for estimating the tungsten sputtering source. In a series of simulations of tungsten transport, the diffusion coefficient D⊥ is varied from 0.1 to 10 m2 s−1, and the hypothetical inward pinch velocity VIMP is in the range of 0–5 m s−1. The tungsten concentration inside the separatrix increases with decreasing diffusion coefficient and exceeds 10−5 for the diffusion coefficient lower than about 0.2 m2 s−1. When the hypothetical inward pinch is included, the tungsten concentration increases. The relation between the relative increase in tungsten concentration and VIMP/D⊥ is fitted. [ABSTRACT FROM AUTHOR]