Abstract:
Background The retention and diffusion of helium on the surface of the first wall is one of the key problems in the study of magnetic confinement fusion. Laser-induced breakdown spectroscopy is the most promising technique for in-situ diagnosis of the first wall. Compared with the optical spectral range, laser-induced extreme ultraviolet spectroscopy has more advantages in sensitivity, noise suppression and accuracy.
Purpose To meet the requirement for high precision on-site measurement of helium impurity lines in magnetic confinement fusion, a ultra-high resolution EUV spectroscopy system was developed.
Methods The grazing incidence Czerny-Turner structure was used in the spectrometer, and the luminous flux and spectral resolution were adjusted through an adjustable incidence slit. The ray tracing simulation was carried out using a self-developed optical design software. And the wavelength calibration and performance testing were carried out by microwave plasma light source.
Results The simulation results show that the spectral resolution is better than 20 000, and the experimental results indicate that the spectrometer achieves a spectral resolution of 0.001 4 nm at He II (30.3786 nm).
Conclusions The spectrometer can meet the requirement for high-precision measurement of helium extreme ultraviolet spectral lines, and it is expected to provide an important theoretical support for the research on the helium retention and diffusion in the first wall.
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