An in situ diagnostic method for monitoring of fuel retention on the first wall under long-pulse operation of experimental advanced superconducting tokamak

Plasma-wall interaction (PWI) research is an active field of study in long-pulse operation in current magnetic confinement fusion devices, such as the Experimental Advanced Superconducting Tokamak (EAST). It is an urgent requirement to be able to investigate several key PWI issues, such as fuel retention, by in situ diagnostic methods. In this work, an in situ diagnostic method of laser-induced breakdown spectroscopy (LIBS) combined with optical emission spectroscopy (OES) is developed. The whole system is applied to study PWI and fill the research gap concerning the correlation between fuel retention and edge plasma conditions during long-pulse plasma operation conditions in EAST. The fuel retention intensity from LIBS on the first wall and the edge plasma condition from OES are monitored simultaneously during the long-pulse plasma operation in EAST. The results indicate that the deuterium (D) retention amount increases as the local edge D particle fluence increases. The results effectively demonstrate the potential of the LIBS method for in situ investigation of the fuel retention for PWI study in upcoming long-pulse fusion devices such as the International Thermonuclear Experimental Reactor (ITER). (topical issue article)