Direct Measurement of Ion Behavior using Modified Ion Sensitive Probe in Tokamak Boundary Plasma

Abstract

Simultaneous measurement of ion temperature and electron temperature as well as correlation with a H α line and the ion behavior are performed by using a modified ion sensitive probe in the boundary plasma in the JFT-2M tokamak. The modified ion sensitive probe for the ion temperature measurement mounted in the JFT-2M can be used to vary the height of the electron barrier for suppressing the electron current by remote control without breaking of the vacuum. The electron temperature is simultaneously measured using the electron guard as a Langmuir probe while the ion temperature is measured by the ion collector of the probe. It has been confirmed that the ion temperature is higher than the electron temperature in the tokamak boundary plasma. It has also been found that the decrease of the ion current at the ion collector coincides with that of the H α line intensity when the plasma confinement is improved during the divertor biasing.