Measurement of natural plasma flow along the field lines in the scrape-offlayer on the JT-60U divertor tokamak

The plasma profile and parallel plasma flow in the scrape-off layer (SOL) w ere systematically measured using reciprocating Mach probes installed at th e outer midplane and near the divertor magnetic null (x point) in the JT-60 U tokamak with a single null divertor. For the ion vertical drift due to th e toroidal magnetic field gradient lion del B drift) directed cowards the d ivertor, SOL plasma flow along the magnetic field lines away from the: dive rtor ("flow reversal") was discovered at the midplane far from the divertor . A quantitative evaluation of the ion "Pfirsch-Schluter now," wherein the parallel flow is naturally produced in a toroidal plasma, was consistent wi th the measurement.