Real time monitoring of material erosion and deposition for the first wall using quartz crystal microbalance in EAST

Two new quartz crystal microbalance (QMB) systems have been installed at different locations in the mid-plane of EAST to measure erosion and deposition of the first wall materials. The two QMBs with different distances from the plasma show complex and distinct erosion and deposition behavior. The QMB in the mid-plane H port closer to the plasma shows a relatively higher net erosion result with an average erosion rate of 1.34 ng/(cm2 s). The normal discharges mainly contribute to the total net erosion and the maximum erosion amount reaches up to 110 ng/cm2 . Contrarily, a slight net deposition of 0.11 ng/(cm2 s) is obtained for the QMB in the mid-plane G port further away from the plasma and the erosion and deposition amount of most discharges are much lower due to lower particle flux. The disruptive discharges lead to a total net deposition rate of 0.48 ng/(cm2 s). Measurement results by the QMBs are demonstrated by a good agreement with the post-mortem analysis by Rutherford Backscattering Spectrometry (RBS).

两套全新的石英晶体微天平（quartz crystal microbalance, QMB）系统已安装于EAST装置中平面的不同位置，用于测量第一壁材料的腐蚀与沉积行为。两套QMB与等离子体的间距存在差异，展现出复杂且迥异的腐蚀与沉积特性。其中，靠近等离子体的中平面H端口QMB，其净腐蚀量相对更高，平均腐蚀速率达1.34 ng/(cm²·s)；正常放电是总净腐蚀的主要来源，最大腐蚀量可达110 ng/cm²。与之相反，远离等离子体的中平面G端口QMB的净沉积速率仅为0.11 ng/(cm²·s)；由于粒子通量更低，多数放电过程的腐蚀与沉积量均显著偏低。破裂放电则带来了0.48 ng/(cm²·s)的总净沉积速率。QMB的测量结果与卢瑟福背散射谱（Rutherford Backscattering Spectrometry, RBS）的事后分析结果具有良好的一致性，验证了测量数据的可靠性。