Change of neutral energy distribution at L-H, H-L transitions and ELM in the JFT-2M tokamak

Abstract

The analyses of the neutral energy distribution measured by the time of flight (TOF) method in the JAERI Fusion Torus 2M (JFT-2M) tokamak are summarized. The TOF technique is also reviewed. Rapid changes of the neutral energy distribution at L-H, H-L transitions, edge localized mode (ELM) and sawtooth crash are observed and these occur earlier than the change of Halpha intensity. This means that the ion energy distribution changes and is playing a very important role at L-H, H-L transitions and ELM. The change of the energy distribution is observed as an increase or decrease of the high energy outflux above an energy of 200 eV. An energy of greater than 200 eV for hydrogen corresponds to the collisionless condition nu *i<1 just inside the separatrix. The observations during an L-H transition from a sawtooth crash to a fall in the Halpha intensity are discussed sequentially