Fuel recycling feedback control via real-time boron powder injection in EAST with full metal wall

A feedback control of fuel recycling via real-time boron powder injection, addressing the issue of continuously increasing recycling in long-pulse plasma discharges, has been successfully developed and implemented on EAST tokamak. The feedback control system includes four main parts: the impurity powder dropper (IPD), a diagnostic system measuring fuel recycling level represented by Dα emission, a plasma control system (PCS) implementing the Proportional Integral Derivative (PID) algorithm, and a signal converter connecting the IPD and PCS. Based on this control system, both active control and feedback control experiments have recently been performed on EAST with a full metal wall. The experimental results show that the fuel recycling can be gradually reduced to lower level as PCS control voltage increases. In the feedback control experiments, it is also observed that the Dα emission is reduced to the level below the target Dα value by adjusting boron injection flow rate, indicating successful implementation of the fuel recycling feedback control on EAST. This technique provides a new method for fuel recycling control of long pulse and high parameter plasma operations in future fusion devices.