Observation and interpretation of core ion cyclotron emission driven by D–D fusion-produced tritium ions in EAST

Abstract Recently, in a series of EAST discharges using deuterium neutral beam injection, tritium (T) ions were produced via deuterium-deuterium (D-D) fusion reactions, resulting in excited ion cyclotron emission (ICE) within the plasma core in H-mode discharge. Experimental studies were conducted under both L-mode and H-mode conditions. In H-mode, ICE excited by T ions was observed with a duration of approximately 5–9 ms; the signal was very strong, and pronounced spectral splitting was clearly visible. In contrast, under L-mode conditions, ICE excited by T ions was not detected following neutral beam injection (NBI). However, an L-H mode transition occurred after NBI injection, leading to the emergence of ICE excited by T ions. Compared with the H-mode with NBI, the ICE signal following the L-H transition was relatively weaker and exhibited no significant spectral splitting but persisted much longer, lasting up to 100 ms. The disappearance of ICE was attributed to degraded plasma confinement, evidenced by decreasing stored energy and increasing plasma radiation. By the way, the enhancement of ICE shows good temporal consistency with the increase in neutron radiation. Furthermore, theoretical analysis based on the magnetized cyclotron instability (MCI) demonstrated that significant growth occurs at the fundamental frequency, providing a quantitative explanation for the observed ICE spectrum. ICE is a valuable potential noninvasive diagnostic for fast-ion behaviour , have important implications for ICE diagnostics of fusion-born fast ions in future fusion devices. The results reported in the this paper have important implications for fast-ion diagnostics in future fusion devices.