High Mach flow associated with X point MARFE and plasma detachment

High Mach flows and their formation mechanism in tokamak divertor regions h ave been studied. Numerical calculations using a two dimensional edge plasm a simulation code (the B2-EIRENE code) have been made for the JT-60U open d ivertor geometry with discharge parameter ranges of relatively low input po wer and L mode experiments. In the high density case, typical formation of an X point MARFE, which is accompanied by plasma detachment, has been obser ved. At the same time, high Mach flows appear near the ionization front, wh ere the plasma static pressure rapidly drops and is far away from the targe t plates. Redistribution from static pressure to dynamic pressure without a large momentum loss is shown to be a possible cause of the high Mach flows observed in the simulation. In addition, a simple 1-D analytic model along the field lines has been applied and the results are compared with the B2- EIRENE results in order to identify the formation mechanism of high Mach fl ows.