Time-resolved triton burnup measurement and preliminary study on EAST

摘要: The scintillating fiber (Sci-Fi) detection system has been implemented on the EAST device to facilitate time-resolved measurements of D-T fusion neutrons. In contrast to the prior approximate estimation of the D-T neutron discrimination threshold, which employed the "Two-Line" method by fitting two decay components to the counting spectrum, a more precise computational approach was developed with the assistance of the neutron activation system. This advancement enhanced the coefficient of determination for the integral yield of D-T neutrons from 0.97 to above 0.99. Furthermore, the comparison between the estimated threshold and the statistically calculated threshold for D-T neutron yield confirmed that the deviation associated with the "Two-Line" method remains below 7%, thereby validating its accuracy and reliability. At the current neutron yield level (S_{n, DD} ~ 10¹⁴), the time resolution capability of the Sci-Fi detection system on EAST is limited, and the conservative estimation is approximately 100 to 200 milliseconds. The triton burnup ratio (R_T) in the flattop region of the plasma current (IP) is markedly higher than the average value over the entire shot. Analysis of two sets of experimental shots with varying IP values indicates a potential positive correlation between R_T and IP, although plasma instabilities exert a significant influence on R_T. Time-resolved investigations further confirmed a rapid increase in the proportion of D-T neutrons within the total neutron yield following the cessation of neutral beam injection heating, and estimated the decay timescale of residual tritons in EAST plasma to be on the order of several hundred milliseconds.