Effect of sheared E  ×  B flow on the blob dynamics in the scrape-off layer of HL-2A tokamak.

The effect of sheared E  ×  B flow on the blob dynamics in the scrape-off layer (SOL) of HL-2A tokamak has been studied during the plasma current ramp-up in ohmically heated deuterium plasmas by the combination of poloidal and radial Langmuir probe arrays. The experimental results indicate that the SOL sheared E  ×  B flow is substantially enhanced as the plasma current exceeds a certain value and the strong sheared E  ×  B flow has the ability to slow the blob radial motion via stretching its poloidal correlation length. The locally accumulated blobs are suggested to be responsible for the increase of plasma density just outside the Last Closed Flux Surface (LCFS) observed in this experiment. The results presented here reveal the significant role played by the strong sheared E  ×  B flow on the blob dynamics, which provides a potential method to control the SOL width by modifying the sheared E  ×  B flow in future tokamak plasmas. [ABSTRACT FROM AUTHOR]