抄録
Quasi-steady state long pulse H-mode discharges with pulse lengths of 5 to 10 second, corresponding to up to about 100 times the energy confinement time have been obtained in the DIII -D tokamak. The so-called Edge Localized Modes (ELMs) play a key role for the long time sustainment through their regulative effect on plasma density, which builds up during the H-mode due to an enhancement of particle confinement. Although the improvement of energy confinement of the ELMy H-mode discharges is somewhat degraded, some of these discharges display a gradual decrease in the overall impurity level throughout the discharge. This effect is significant since it prevents radiation collapse in present devices and should mitigate fuel dilution in future machines. This paper reviews the status of the DIII-D long pulse H-mode experiments and summarizes understandings of the physics and phenomenology of ELMs including impurity behaviour. A brief introduction to the Advanced Divertor (AD) system is also given. Initial operation of AD allowed DIII-D to demonstrate an increased particle flow to the divertor baffle chamber when electrical bias was applied.
