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

Abstract

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/(cm2s). 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/(cm2s) 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/(cm2s). Measurement results by the QMBs are demonstrated by a good agreement with the post-mortem analysis by Rutherford Backscattering Spectrometry (RBS).

Keywords

• Erosion and deposition
• Real time monitoring
• QMBs
• RBS