Metallic first mirrors (FMs) make up important components in many of the optical diagnostic systems in the fusion reactor ITER. They are responsible for directing the light from the fusion plasma towards the diagnostic sensors through an optical labyrinth to prevent neutron leakage. However, being the initial elements in the optical path, the FMs are subject to constant erosion from charge exchange neutrals as well as deposition of the first wall materials: beryllium (Be), tungsten (W) and their oxides, which would significantly degrade their optical properties. Read more
