Development of a spatial heterodyne spectrometer for time-resolved measurement of Zeeman effect on Hα emission line spectra

•Optimizing spectrometer parameters doubles etendue over conventional designs.•A modified method sums sub-spectra to improve spectrum measurement.•The constructed SHS achieves 4 × better SNR than a Czerny-Turner spectrometer.•The modified method fits Zeeman-effect spectra well without phase correction or apodization. A spatial heterodyne spectrometer (SHS) for measuring the Zeeman effect on Hα emission line spectra was developed using an optimization design method that maximizes the product of the resolving power and etendue. Modified data processing steps were also used to improve the signal-to-noise (S/N) ratio of the spectra. The S/N ratio of the developed SHS was evaluated by measuring Ne I emission line spectra and compared with that of a Czerny–Turner spectrometer (CT) at a comparable resolving power. The results indicated that the S/N ratios of SHS spectra were approximately four times higher than those of CT spectra over an exposure time range of 0.5−80 ms. Additionally, Hα emission line spectra with the Zeeman effect were measured at magnetic field strength of 1−3 T comparable to that in a confinement device. It was confirmed that the theoretical instrumental function with a measured instrumental width can be used to analyze the line shape of multiple emission splitting lines.