Hollow Density Profile on Electron Cyclotron Resonance Heating JFT-2M Plasma

The first hollow electron density profile in the central region on the JAERI Fusion Torus-2M (JFT-2M) is measured during electron cyclotron resonance heating (ECRH) with a TV Thomson scattering system (TVTS). The peripheral region is not hollow but is accumulated due to pump-out from the central region. The hollowness increases with time but is saturated at ~40 ms and maintains a constant hollow ratio. The hollowness is strongly related to the steep temperature gradient of the heated zone.