Plasma characteristics near the X-point in W-shaped divertor of JT-60U

A reciprocating Langmuir probe was installed below the X-point of W-shaped divertor in JT-60U. Plasma profiles were measured from the outer divertor n ose to the X-point. A large peak was observed in the density profile near t he X-point as the main plasma density exceeded about 60% of MARFE onset den sity. The electron density at the peak exceeded the average density of the main plasma. The difference in electron temperature between the X-point and the outer target was smaller at the separatrix than outside the separatrix . The electron temperature near the separatrix decreased rapidly from 60 to 20 eV as the density peak increased. The electron temperature profile beca me flat and decreased down to similar to 10 eV during a MARFE. (C) 1999 Els evier Science B.V. All rights reserved.