Electron energy distribution function measured by electrostatic probes at divertor plasma in JFT-2M tokamak

The electron energy distribution function (EEDF) as well as the plasma parameters were measured by the electrostatic probe for divertor plasmas in the JFT-2M tokamak. The necessary condition for obtaining the precise EEDF including a wide range of electron energy is studied, in which the electrostatic probes should be placed in the region where the ratio of the electron saturation current to ion saturation current is sufficiently large. The behaviors of the EEDF estimated from the first derivative of the probe current were discussed for the ohmic heated (OH) and the electron cyclotron resonance heated (ECRH) plasmas. (author)