Reversed-slit spectroscopy method for in situ measurement of H isotopes on plasma facing material

Optic spectroscopy methods are employed for plasma facing component (PFC) material diagnostics and H isotopes retention on various platforms. A common issue of those spectroscopy methods is the measurement sensitivity. Various improvement methods have been investigated. In the current work, a 'reversed-slit' method is explored, aiming to maximise signal input while retain a reasonably good line resolution. A thin metal wire with a diameter that is comparable to a normal slit width is placed in front of an open slit. By opening the slit the input of the emission light is maximised. The thin wire casts a line of shadow on the spectral image. The shadow line is used as the 'characteristic line' to identify and separate the spectral line of each H isotope. The result shows that an open slit of 3 mm width can bring an intensity increase of 20–30 times compared to a 100 μm wide normal slit without compromising the resolution.