Simulation of divertor pumping in JT-60U with SOLDOR/NEUT2D code

To characterize the divertor pumping for particle and heat control in the SOL/divertor and to extrapolate to future devices, simulations using the SOLDOR/NEUT2D code are performed on the JT-60U experiment. The simulation reproduces fairly well the neutral pressure and pumping flux in the exhaust chamber. A parametric survey shows that the pumping efficiency ηpump (ratio of pumping flux to generated flux around the divertor targets) increases with the pumping speed. It is found that a pumping speed higher than the present capability (26 m3/s) is necessary for the active particle control under the wall saturation condition. When the strike-point distance is shortened from 10 to 2 cm, the ηpump is enlarged by a factor of 1.5 with increase of the slot view angle. A virtual tilt of the divertor targets to 15° vertically enhances ηpump by a factor of 1.2 and leads simultaneously to a lower target heat load.