Abstract
By using the recently developed Thomson scattering diagnostic, the pedestal structure of the H-mode with neutral beam injection (NBI) or/and lower hybrid wave (LHW) heating on EAST (Experimental Advanced Superconducting Tokamak) is analyzed in detail. We find that a higher ratio of the power of the NBI to the total power of the NBI and the lower hybrid wave (LHW) will produce a large and regular different edge-localized mode (ELM), and a lower ratio will produce a small and irregular ELM. The experiments show that the mean pedestal width has good correlation with , The pedestal width appears to be wider than that on other similar machines, which could be due to lithium coating. However, it is difficult to draw any conclusion of correlation between ρ* and the pedestal width for limited ρ* variation and scattered distribution. It is also found that Te/Te is ~2 cm, which is the same as the AUG (ASDEX Upgrade), DIII-D and JET (Joint European Torus) results.
Highlights
The high confinement regime H-mode is one of the most promising scenarios for tokamak operation
When the RNT is higher than 67%, the frequency of the edge-localized mode (ELM) increases slowly with increasing the total power, which is similar to the type I ELMy H-mode, while when the RNT is lower than 55%, the lower hybrid wave (LHW) begin to dominates the heating, and the frequency of ELMs increases dramatically with increasing of total power, which is similar to the type III ELMy H-mode
A πB0 are defined as those given by DIII-D and the flux coordinates come from the results of the EAST EFIT calculation
Summary
The high confinement regime H-mode is one of the most promising scenarios for tokamak operation. The pedestal is a remarkable feature of H-mode confinement in tokamak edge plasmas, and is assumed to be associated with high performance and achievable central temperature. The pedestal structures of type I ELM and type III ELM H-mode discharges, which are by far the most common two high confinement regimes on EAST, are mainly discussed in this paper. This is the first systematic study of the pedestal structure on EAST, and three pedestal characteristics—the value at the transition to the core plasma (pedestal height), the extent of the pedestal region (pedestal width) and the gradient of the pedestal—are analyzed with. Other plasma properties, some results of these analyses are compared with various theories, and the major influences on the pedestal structure are discussed
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