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 ultra-violet (EUV) spectrometers working at 5-138 angstrom were newly established on EAST tokamak. A back-illuminated complementary metal oxide semiconductor (CMOS) detector with a small pixel size of 6.5 x 6.5 mu m2 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 angstrom and Cu XXI at 10.392 angstrom 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.

Automated summary

Two pairs of space-resolved extreme ultra-violet (EUV) spectrometers were newly established on EAST tokamak to observe the radial profile of impurity line emission in a short wavelength range and study the transport of metallic impurity ions in plasma. The spectrometers, equipped with a back-illuminated complementary metal oxide semiconductor (CMOS) detector and a varied-line-spacing (VLS) concave holographic grating, demonstrated excellent performance in impurity diagnostics. The radial intensity profile of Cu XX and Cu XXI at different wavelengths was successfully observed, as well as the rapid change in the radial profile of W XXXIII during the impurity burst period.