MEASUREMENT OF EDGE PLASMA PARAMETERS AND THEIR ELECTROSTATIC FLUCTUATIONS ON THE HT-7 SUPERCONDUCTING TOKAMAK

Abstract

The radial profiles of the electron temperature Te,the electron density ne,the plasma potential φp,the toroidal Mach number Mp and their electrostatic fluctuations in the plasma boundary region of the HT-7 superconducting tokamak have been measured with a multiarray of Langmuir probes and a set of Mach probes,under the conditions of both ohmic discharge and a lower hybrid current drive.The experimental results show that,under ohmic discharge condition,there is a poloidal velocity shear layer located in the vicinity of the limiter radius,which has a suppression effect on the fluctuations and results in the increase of the radial gradients of Te and ne LHCD intensifies the shear.In the same radial position of the poloidal shear layer,there is also a radial shear with the toroidal velocity,which could be the drive source of the mean poloidal flow needed by the formation for radial electric field.