Narrowband EUV Sc/Si Multilayer for the Solar Upper Transition Region Imager at 46.5 nm

• Published in: Research in astronomy and astrophysics Vol. 23; no. 10; pp. 105002 - 217
• Main Authors: Qi, Runze, Wu, Jiali, Yu, Jun, He, Chunling, Jiang, Li, Yu, Yue, Zhang, Zhe, Huang, Qiushi, Zhang, Zhong, Wang, Zhanshan
• Format: Journal Article
• Language: English
• Published: Beijing National Astromonical Observatories, CAS and IOP Publishing 01.10.2023; IOP Publishing; Institute of Precision Optical Engineering,School of Physics Science and Engineering,Tongji University,Shanghai 200092,China; Key Laboratory of Advanced Micro-structured Materials,Ministry of Education,Tongji University,Shanghai 200092,China
• Subjects: Astronomical Instrumentation; Corona; instrumentation: high angular resolution; Lower atmosphere; Methods and Techniques; Multilayers; Narrowband; Primary mirrors; Reflectance; Secondary mirrors; Solar atmosphere; Spectral resolution; Sun: UV radiation; Temporal resolution; Sun:UV radiation; instrumentation:high angular resolution; Astronomical Instrumentation; Methods and Techniques
• ISSN: 1674-4527; 2397-6209
• DOI: 10.1088/1674-4527/acee4e

The transition region is the key region between the lower solar atmosphere and the corona, which has been limitedly understood by human beings. Therefore, the Solar Upper Transition Region Imager (SUTRI) was proposed by Chinese scientists and launched in 2022 July. Right now, the first imaging observation of the upper transition region around 46.5 nm has been carried out by SUTRI. To ensure the spectral and temporal resolution of the SUTRI telescope, we have developed a narrowband Sc/Si multilayer. Based on the extreme ultraviolet (EUV) reflectivity measurements, the multilayer structure has been modified for ensuring the peak position of reflectivity was at 46.5 nm. Finally, the narrowband Sc/Si multilayer was successfully deposited on the hyperboloid primary mirror and secondary mirrors. The deviation of multilayer thickness uniformity was below than 1%, and the average EUV reflectivity at 46.1 nm was 27.8% with a near-normal incident angle of 5°. The calculated bandwidth of the reflectivity curve after primary and secondary mirrors was 2.82 nm, which could ensure the requirements of spectral resolution and reflectivity of SUTRI telescope to achieve its scientific goals.