An upgrade to the lower divertor is currently being planned for EAST superconducting tokamak, aiming at reaching over 400 s long-pulse H-mode operations with a full metal wall and a divertor heat load of ˜10 MW/m2. A new divertor concept for EAST, “Tightly Baffled Divertor”, suited to water- cooled W/Cu plasma face components (PFC) with minimized divertor volume, has been proposed to achieve Te,target <5 eV across entire outer target at lower separatrix plasma density and optimized pumping by a simple closed divertor structure combining horizontal target with inclined baffle, dome and duct. This divertor should allow access to high-triangularity small Edge Localized Mode (ELM) H-mode regimes and also allow achieving advanced magnetic divertor configurations with the assistance of two water-cooled in-vessel divertor coils (Divertor coils). Preliminary engineering design of in-vessel Divertor coils indicates a maximum current of 8 kA for long-pulse discharges, and 20 kA for the shortest ones. However, flexibility on Divertor coils position optimization is limited to the water cooling system. Initial plasma equilibrium studies by EFIT code, used in combination with CREATE-NL and FIXFREE tools, show that the distance of the two nearby divertor poloidal field nulls, can be decreased up to ˜ 0.95 m with a plasma current IP ˜ 400 kA, leading to a configuration with the secondary X-point located close to the target, with a significant increase of magnetic poloidal flux expansion and connection length. This may provide a promising divertor solution compatible with advanced steady-state core scenarios.
|Titolo:||Progress on in-vessel poloidal field coils optimization design for alternative divertor configuration studies on the EAST tokamak|
|Data di pubblicazione:||2019|
|Appare nelle tipologie:||1.1 Articolo in rivista|