Work

Study on erosion and deposition processes of lithium in magnetic shadow region on EAST

Year: 2026

Type: article

Abstract: The plasma–wall interaction in the magnetic shadow regions can influence phenomena such as fuel retention, though the role of neutral particle dynamics in the process remains scarcely quantified. Through a novel multi-diagnostic approach, this study investigates how neutral-induced erosion and impurity deposition modulates material migration behind limiters. By modifying and installing custom-designed Quartz crystal MicroBalances (QMBs) on the head of the Material and Plasma Evaluation System located at the equatorial port of sector H in EAST, the in-situ measurement of the erosion and deposition results of the lithium (Li) at different radial positions was performed. The average mass loss rates of the QMB crystal were −9.84 × 10 −1 ng cm −2 s −1 , 2.54 ng cm −2 s −1 , and 2.15 ng cm −2 s −1 at three locations with major radii of 2584 mm, 2784 mm, and 2734 mm, respectively. A clear transition from deposition to erosion was observed as the distance between QMB and plasma increased. Notably, the neutral-induced Li erosion rate was calculated using the 3D-GAPS code. The results prove that, in addition to the influence of plasma parameters on neutral-induced material erosion by varying the neutral energy spectrum, the radial position of the QMB also affects neutral-induced material erosion by changing the solid angle and the angle-dependent sputtering yield. This supports the existence of a limiter-adjacent impurity deposition zone, with material erosion by neutrals acting as a potential fuel retention mitigation mechanism. This work establishes the quantitative framework connecting neutral transport with wall material evolution, providing critical insights for next-step devices like ITER to optimize fuel retention amount.

Source: Nuclear Fusion

DOI: 10.1088/1741-4326/ae5c1a