1：Experimental Design and Method Selection:

The study used Laser Induced Breakdown Spectroscopy (LIBS) with a single pulse technique to analyze deuterium retention. The experimental layout involved remote measurements from approximately 2.5 meters away through a port, with collinear transmission of the laser beam and detection of emitted light using a dielectric mirror. The aim was to detect spectral lines, particularly Dα and Hα, under high vacuum, nitrogen, or argon atmospheres.

2：5 meters away through a port, with collinear transmission of the laser beam and detection of emitted light using a dielectric mirror. The aim was to detect spectral lines, particularly Dα and Hα, under high vacuum, nitrogen, or argon atmospheres. Sample Selection and Data Sources:

2. Sample Selection and Data Sources: The samples were the Mo (TZM) toroidal limiter tiles in the FTU tokamak, consisting of twelve sectors with 30 tiles each. Measurements were conducted during short breaks in operations or machine maintenance, focusing on accessible points from an equatorial port.

3：List of Experimental Equipment and Materials:

Equipment included a Quantel "Twin BSL" laser (λ = 1064 nm), a sapphire window for laser transmission, a dielectric mirror for light detection, a bundle of 12 optic fibers (100 μm core), a Jobin Ivon "Triax 550" spectrometer (550 mm with 2400 grooves/mm grating), and an Andor "Istar DH320T-18F-63" ICCD camera (1024 × 512 sensor). Materials involved the FTU vacuum vessel, nitrogen, and argon gases for atmospheric conditions.

4：Experimental Procedures and Operational Workflow:

The laser was fired to generate a plasma plume on the limiter tiles. The emitted light was focused onto optic fibers and analyzed by the spectrometer. Measurements were performed under vacuum (～10^{-5} Pa), nitrogen (105 Pa), and argon (5 × 10^4 Pa) atmospheres. Timing and parameters were adjusted based on machine availability, with detection gate delays varied (e.g., 300 ns, 350 ns, 2000 ns) to optimize signal acquisition.

5：Data Analysis Methods:

Spectral data were analyzed to identify and resolve Dα (656.11 nm) and Hα (656.28 nm) lines. In some cases, Voigt fitting was used to estimate electron temperature and density. Relative concentrations were calculated using an internal standard method with deuterium, and the Calibration Free (CF) method was considered but not fully applied due to limitations.