2026 年 21 巻 論文ID: 1402045
A near-infrared (NIR) spatial heterodyne spectrometer was developed for the hydrogen Paschen-α emission line (Paα, 1,875 nm) to enable temporally and spatially resolved measurements of hydrogen atomic density, temperature, and flow velocity in the edge region of magnetically confined fusion plasmas. To overcome the frame-rate limitations of two-dimensional NIR image sensors, an indium gallium arsenide (InGaAs) linear array was employed, and the interferogram was compressed into one dimension using a custom cylindrical imaging lens system. Spectral measurements of Ne I emission lines in a glow discharge tube confirmed an instrumental wavelength resolution of 125 pm. At zero magnetic field, the measured Paα interferogram in the glow discharge tube exhibited a contrast ratio of approximately 0.58, demonstrating agreement with the numerical model. Furthermore, spectral measurements under magnetic fields up to 3 T demonstrated that spectra influenced by the Zeeman effect were reproducible using fitting functions that incorporate the instrumental function and Doppler broadening. Despite a magnetic field-induced contrast-ratio degradation to approximately 0.4, a signal-to-noise ratio of approximately 20 was achieved at a 1-ms exposure time for a spectral radiance of 1.2 W m−2 sr−1 nm−1, which is comparable to the emission expected in the ITER divertor region.
