Analysis of particle pumping using SOLDOR/NEUT2D code in the JT-60U tokamak

Kawashima, Hisato; Shimizu, Katsuhiro; Takizuka, Tomonori

To characterize the divertor pumping for particle control in the SOL/divertor and to extrapolate to future devices, simulations using the SOLDOR/NEUT2D code are performed on JT-60U. It reproduces fairly well the neutral pressure and pumping flux in the exhaust chamber at experiment. It shows that higher pumping capability within is necessary for active particle control. In order to improve pumping capability, we analyze the inward/outward neutral flux into/from the exhaust chamber with introducing the pumping efficiency (pumping flux/generating flux). We find that the efficiency is increased by shortening the distance from pumping slot to strike point on the target or tilting the targets vertically. For the design study of JT-60SA divertor, an increase of the efficiency is indicated with narrowing the pumping slot width. To understand these phenomena, we are identifying the role of neutral processes such as ionization, charge-exchange and so on.