Reversal of in–out asymmetry of the particle-recycling associated with X-point MARFE and plasma detachment

Abstract Reversal of in–out asymmetry of the particle recycling in tokamak divertor regions and its physical mechanism have been studied. Numerical calculations by the `B2-EIRENE' code have been done for the JT-60U open divertor geometry. The following two cases, n D =1.0×10 19 m −3 and n D =2.0×10 19 m −3 for the D+ ion density at the core interface boundary, have been calculated. In the high-density case, typical behaviors of X-point MARFE and plasma detachment have been observed. In addition, asymmetry of the particle recycling between the inner and the outer divertor regions is reversed in comparison with the low-density case. The difference of the electron temperature between the inner and the outer regions together with the Te-dependence of the ionization rate coefficient is shown to be a possible cause of the reversal of the recycling source. Also, the difference of pressure loss between two regions plays a key role in the in–out asymmetry of the particle flux at the plate.