Analysis of impurity distribution and composition on a gas puffing pipe for Lower Hybrid Wave system in EAST by LIBS approach

Abstract Impurities generated by plasma-wall interactions significantly impact the performance of nuclear fusion devices by increasing radiation and dilution of plasma while also forming co-deposited layers on plasma-facing components that retain critical hydrogen isotopes like tritium. This study utilized laser-induced breakdown spectroscopy (LIBS) to investigate impurity distribution and composition on the surface of the gas puffing pipe (GPP) for the Lower Hybrid Wave system in the Experimental Advanced Superconducting Tokamak (EAST) tokamak during the 2021 experimental campaign. Elemental analysis found impurities (Cu, W, Mo, C, and Li) originating from specific components and materials in the EAST. Further analysis revealed complex co-deposition patterns, where impurity levels increased from a melt region, peaked near the melt region, and then decreased toward the end of the pipe. This distribution indicates a dynamic competition between erosion and deposition processes. Spatial analysis further revealed higher impurity concentrations on the ion side of the pipe compared to the electron side, likely due to differences in plasma interactions. To achieve quantitative measurements of impurities, one-point calibration LIBS (OPC-LIBS) was utilized to enhance the analytical accuracy of impurity deposition on the GPP. The results confirm that OPC-LIBS is an applicable approach for the quantitative analysis of impurity deposition in fusion devices.