Investigation of 3D elemental distribution on the dome surface of HL-2A divertor by laser-induced breakdown spectroscopy

In this work, three-dimensional (3D) diagnostics of the graphite tile surface elements in the dome region of the HL-2A divertor in both poloidal and toroidal directions were investigated using laser-induced breakdown spectroscopy (LIBS) technology under simulated HL-2A vacuum conditions. LIBS spectroscopic analysis revealed the presence of impurity elements such as Si, Cu, Ca, Al, Fe, Cr, Ni, and Mn on the graphite tile surface. Depth profile results of the impurity deposited layer on the shoulder part of graphite tile showed that Fe, Cr, Ni, and Mn emission intensities gradually decreased and disappeared with depth. The Si, Cu, Ca, and Al initially increased, then decreased, and eventually disappeared in the depth profile. Two-dimensional (2D) depth profile results of impurity elements in the poloidal direction showed significant asymmetry in impurity deposition within 70 mm of the shoulder and 20 mm from the top, and the impurity layer thickness on the shoulder greater than that on the top (approximately 5.7 μm vs. 3.1 μm). Further 3D imaging of the surface elements of the HL-2A divertor demonstrated strong asymmetry of impurity elements on the graphite tile surface in the poloidal direction, but no significant asymmetry was observed in the toroidal direction within 50 mm.