Development of space-resolved EUV spectrometers working at 5–138 Å for profile observation of high-Z impurity ions in EAST plasma

In order to observe the radial profile of impurity line emission in a short wavelength range and to study the transport of metallic impurity ions intrinsically existing in plasma, two pairs of space-resolved extreme ultraviolet (EUV) spectrometers working at 5–138 Å were newly established on EAST tokamak. A back-illuminated complementary metal oxide semiconductor (CMOS) detector with a small pixel size of 6.5 × 6.5 μm2 and a varied-ling-spacing (VLS) concave holographic grating with a central density of 2400 grooves/mm allows the EUV spectrometers have good spectral resolution. A precise wavelength calibration is performed with cubic polynomial fitting using well-known emission lines from light impurity ions. The radial intensity profile of Cu XX at 12.570 Å and Cu XXI at 10.392 Å were observed successfully by space-resolved EUV spectrometers during H-mode discharge. The rapid change in the W XXXIII radial profile during the impurity burst period was clearly observed with sufficient intensity. The results show that the newly developed space-resolved EUV spectrometers have excellent performance in impurity diagnostics.