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The assessment of material deposition and fuel retention on Plasma Facing Components (PFCs) is of primary importance for the steady-state operations of future fusion devices. In this paper, an in situ diagnostic for mapping the deposition distribution (IMap) on a wide area of PFCs for HL-2M (Huan Liu Qi-2 Modification) is developed. The design, fabrication, integration, and lab test of the IMap have been implemented. This system is built with the laser-induced breakdown spectroscopy technique which is an in situ diagnostic technique to determine the constituents and the depth profile of deposition compositions on PFCs. With a molybdenum reflection mirror inside the chamber and its manipulator, the IMap system can scan from the inner wall across the lower divertor to the outer middle plane. The system can be remotely controlled, and its optical lenses, mirrors, and fibers can be adjusted automatically when scanning over the PFCs. Therefore, the wall properties over a wide area of the vessel can be measured. All elements with the emission lines in the range of 380–850 nm can be analyzed, and the isotope species H and D can also be identified clearly with this diagnostic. Moreover, the depth profiles of the deposited materials can be determined, and the fuel retention on PFCs can be evaluated in situ. This gives a clear picture of the deposition and retention over the wall of HL-2M.

The first wall is one of the key components in a tokamak, in particular, for DEMO in the future. The conceptual first wall for a DEMO reactor is designed, fabricated and tested in this paper. It has a sandwich-like structure, which consists of a reduced activation ferritic/martensitic (RAFM) substrate, an interlayer and a plasma-facing material of tungsten produced by chemical vapor deposition (CVD-W) due to its characteristics of high density, high purity and superior thermal shock resistance. The interlayer is required to not only have good adhesion between CVD-W and the CLF-1 substrate, which is a type of RAFM developed by the Southwestern Institute of Physics, but also the capability of tritium transport prevention due to the great importance of controlling the tritium buildup in the first wall, improving the fuel efficiency and conforming to the safety regulations of tritium. Titanium nitride (TiN), a well-known tritium barrier, is selected as the interlayer material in this work. In total, eight sandwich-like first wall samples have been fabricated, and thermal cycle tests and plasma exposure tests are implemented. The results of material analysis show that the quality of the TiN coating layer is critical for good adhesion and tritium prevention. At the defects of the TiN interlayer, fluorine (F) penetrated into the CLF-1 during the CVD-W fabrication and, as a result, the sandwich-like structure was broken near the CLF-1 side. For some samples, the TiN interlayer made by CVD has sufficient adhesion as an interlayer between CVD-W and CLF-1 during tests so far. These encouraging test results support further examination of TiN as an interlayer material for W on an RAFM steel as a first wall material. Preliminary results indicate that the design and fabrication of the conceptual first wall are feasible. Further tests, including the improvement of the interlayer quality and the tritium permeation test, are necessary in the future.