Geometry and Physics Design of Lower Divertor Upgrade in EAST

Experimental advanced superconducting tokamak (EAST) device is a D-shaped full superconducting tokamak with actively water cooled plasma-facing components. Before this upgrade, three generations divertors, which are steel divertor, carbon divertor, and international thermonuclear experimental reactor-like upper divertor, have been applied, respectively. To achieve long-pulse and high-beta H-mode plasma, new plasma configurations and shapes have been modeled and optimized in 2016 on EAST. The new geometry of lower divertor heavily relies on numerical simulations of the plasma in EAST. The new divertor is designed to fit the high-beta H-mode plasma and endure the heat flux up to 10 MW/m(2). To achieve this goal, the lower carbon divertor will be replaced in EAST, which is now in conceptual design phase. Compared to the outer target side, the inner target side is prone to plasma detachment. First, the geometry and physics of the divertor should be better designed with the advanced physical operation mode. Second, the divertor should be in advanced geometry and high efficient cooling structure. Third, considering balance the detachment between inner target side and outer target side. This paper mainly introduces the research progress of the fourth-generation tungsten divertor in EAST.