CYRA (CrYogenic solar spectrogRAph) is a facility instrument of the 1.6-meter Goode Solar Telescope (GST) at the Big Bear Solar Observatory (BBSO). CYRA focuses on the study of the near-infrared solar spectrum between 1 and 5 microns, an under-explored region which is not only fertile ground for photospheric magnetic diagnostics but also allows a unique window into the chromosphere lying atop the photosphere. CYRA is the first-ever fully cryogenic spectrograph in any solar observatory with its two predecessors, on the McMath-Pierce and Mees Telescopes, being based on warm optics except for the detectors and order sorting filters. CYRA is used to probe magnetic fields in various solar features and the quiet photosphere. CYRA measurements will allow new and better 3D extrapolations of the solar magnetic field and will provide more accurate boundary conditions for solar activity models. The superior spectral resolution of 150,000 and better allows enhanced observations of the chromosphere in the carbon monoxide (CO) spectral bands and will yield a better understanding of energy transport in the solar atmosphere. CYRA is divided into two optical sub-systems: The Fore-Optics Module and the Spectrograph. The Spectrograph is the heart of the instrument and contains the IR detector, grating, slits, filters, and imaging optics all in a cryogenically cooled Dewar (cryostat). The sensor is a 2048 by 2048 pixel HAWAII 2 array produced by Teledyne Scientific and Imaging, LLC. The cryostat interior and the readout electronics are maintained at 90 Kelvin by helium refrigerant-based cryo-coolers, while the IR array is cooled to 30 Kelvin. The Fore-Optics Module de-rotates and stabilizes the solar image, provides scanning capabilities and transfers the GST image to the Spectrograph. CYRA has been installed and is undergoing its commissioning phase. This paper reports on the design, implementation, and operation of CYRA in detail. The preliminary scientific results have been highlighted as well.
Sc/Si multilayer has excellent reflectivity at the wavelength of 35-50 nm and is expected to be fabricated for application in the solar EUV telescope, reflecting Ne VII line (46.5 nm) at normal incidence angle. For obtaining the stable narrow bandwidth, Sc/Si multilayers with different Sc thickness ratios were designed. And the structure and temporal stability of fabricated multilayers were studied. Sc/Si multilayers with a period thickness of about 24 nm were deposited by DC magnetron sputtering. The GIXR measurements indicated that interface diffusion was existed between Sc and Si layers. As the thickness ratio of the Sc increased, the width on Sc-on-Si interfaces increased. The surface roughness of these samples were no obviously different under AFM tests. After two months, the periodic structure and thickness were found to be stable. With a Sc thickness ratio value of 0.67, Sc/Si multilayer not only have the narrow bandwidth, but also have a good temporal stability.
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