**4. Discussion/conclusion**

Because of safety issue, it is important to understand how and where tritium will be stored in tokamaks due to plasma‐wall interaction. In this chapter, we have demonstrated the ability of Rama microscopy to detect and characterize material changes subsequently to interac‐ tion with hydrogen, for both carbon‐based tokamaks and for ITER‐like wall materials (tung‐ sten that is oxidized and beryllium). The comparison between well‐controlled samples and sample extracted from tokamak has been used to better characterize some of the tokamaks' properties.

Among other findings, we report that by changing temperature on various carbon samples, extracted from tokamak (Tore Supra) or comparative reference laboratory samples (a‐C:H) synthesized in controlled conditions, we have shown how Raman spectroscopic parameters can be used to characterize structural and H‐content evolution/changes.

We also report that beryllium hydrides that can form high tritium reservoir in tokamaks can be formed and detected under ion implantation.

To conclude, next studies will have to use different laser wavelengths as they can be used to probe gradients of properties in the beryllium's depth due to the fact the depth probed is in the range of few tens of nanometer. This is the typical depth at which a high content of hydro‐ gen isotope is found in modern tokamak samples like JET. Future studies have to be driven with this technique to better characterize the so‐called supersaturated layer.
