Features and initial results of the EAST divertor plasma experiments

The first dedicated divertor physics experiments were carried out on Experimental Advanced Superconducting Tokamak (EAST) in April 2009. Detailed measurements of plasma parameters at the divertor targets were made using an extensive array of divertor diagnostics, and some insights into several divertor physics issues were gained. This work was focused primarily on ohmic discharges. The behavior of divertor plasma, power asymmetry between inner and outer targets, and different fueling methods were investigated in both single null (SN) and double null (DN) divertor discharges. Divertor plasma detachment was achieved, for the first time on EAST, by ramping up the density during the discharge with well controlled, steady divertor configuration. The screening of carbon has been studied by puffing methane into the divertor. In addition, radiative divertor experiments were performed by localized argon injection, leading to a significant reduction in the heat flux on the target plates due to enhanced radiation in the divertor. This provides a means to avoid excess heat load on divertor components, specifically the divertor target tiles, which is essential for high power and long pulse operations, as envisioned for EAST.