The Visible Spectro-Polarimeter of the Daniel K. Inouye Solar Telescope

Wijn, A. G. de; Casini, R.; Carlile, A.; Lecinski, A.; Sewell, Scott; Zmarzly, P.; Eigenbrot, Arthur; Beck, C.; Wöger, Friedrich; Knölker, M.

doi:10.1007/s11207-022-01954-1

Cited by 26 publications

(8 citation statements)

References 61 publications

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“…The visible spectro-polarimeter (ViSP) is a three-arm, slit-based spectropolarimeter currently on offer for science observation and summarized by de Wijn et al. 18 The diffraction-limited near-infrared spectro-polarimeter (DL-NIRSP) is a fiber-optic-based integral field spectropolarimeter. 19 The cryogenic near-infrared spectro-polarimeter (Cryo-NIRSP) is a slit based system optimized for the infrared.…”

Section: Overview Of Dkistmentioning

confidence: 99%

Large aperture optically contacted MgF2 retarders for calibration and modulation at DKIST

Harrington

2023

J. Astron. Telesc. Instrum. Syst.

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Modern astronomical polarimeters often require simultaneous operation of multiple instruments over broad wavelength ranges. The 4 m DKIST solar telescope will soon cover 0.38 to 4.6 μm with at least 12 independent narrow band polarimeters, all in quasi-simultaneous operation. Calibration can be efficiently performed over this entire bandpass using our elliptical retarder design, achieved with just two optically contacted MgF 2 crystal retarder pairs. Calibration requires very well-characterized, uniform, defect-free retarders and polarizers. I report here on the successful development of four extremely large aperture (d ¼ 120 mm) optically contacted MgF 2 retarder pairs used to make a DKIST calibrator and a modulator for the Cryo-NIRSP instrument. All four crystal pairs have clear apertures free of defects. New procedures deliver fast axis alignment in the range of 0.1 deg to 0.2 deg post contact bonding. For the calibrator crystals, a new process was developed using deterministic fluid jet polishing driven by retardance mapping to achieve stringent retardance spatial uniformity. I show that transmitted wavefront error is not a sufficient proxy for retardance polishing. Polishing softer MgF 2 retarder crystals required substantial development to simultaneously achieve flatness, roughness, and retardance uniformity. The optical contact bond ensures there are no bonding agents (oils, epoxies) with spectral absorption bands in the entire 0.3 to 6 μm bandpass without any possibility for leaks or degradation. These four crystals will be used in DKIST and Cryo-NIRSP in a 300 W solar beam and are anticipated to mitigate heating, stability, and UV irradiation issues. I use the Berreman calculus to compute retarder depolarization, with >10% magnitudes found at the shortest wavelengths after including typical crystal optic axis cutting errors and incidence angle variation in converging beams.

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Section: Overview Of Dkistmentioning

confidence: 99%

Large aperture optically contacted MgF2 retarders for calibration and modulation at DKIST

Harrington

2023

J. Astron. Telesc. Instrum. Syst.

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“…Cryo-NIRSP is one of the five first-generation instruments at the DKIST -the others being the Visible Broadband Imager (VBI: Wöger et al, 2021), the Visible Spectro-Polarimeter (ViSP: de Wijn et al, 2022), the Diffraction Limited Near Infrared Spectro-Polarimeter (DL-NIRSP: Jaeggli et al, 2022) and the Visible Tunable Filter (VTF: von der Lühe et al, 2023). As the name suggests, Cryo-NIRSP is cooled to below 77 K to minimize the thermal background in the observations.…”

Section: Introductionmentioning

confidence: 99%

The Daniel K. Inouye Solar Telescope (DKIST) Cryogenic Near-Infrared Spectro-Polarimeter

et al. 2023

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The Cryogenic Near-Infrared Spectro-Polarimeter (Cryo-NIRSP) is a combination slit-based spectrograph and context-imaging instrument designed and built for the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST). It is optimized for polarimetric observations of spectral band-passes between 1 and 5 microns, which makes it uniquely suited for polarimetric observations of the solar corona, while also enabling access to other important infrared diagnostics such as the CO fundamental band at 4.6 microns. Integration, testing, and commissioning occurred between 2019 and 2020, and it is now conducting science experiments as part of DKIST early operations. In this article, we discuss its science mission, the requirements driving the design, its fabrication and installation, current capabilities, and the first science data.

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“…The present contribution to the subject adds to this body of knowledge by providing a unique glimpse at high spatial, spectral, and temporal resolution of 10 minutes in the hour or two lifetime of a mature umbral flash. This is achieved by employing the inaugural Science Verification (SV) data from the Visible Spectro-Polarimeter (ViSP; De Wijn et al 2022), attached to the NSF Daniel K. Inouye Solar Telescope (DKIST; Rimmele et al 2020).…”

Section: Introductionmentioning

confidence: 99%

First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP: The Anatomy of an Umbral Flash

French

Bogdan

Casini

et al. 2023

ApJL

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The Visible Spectro-Polarimeter of the NSF Daniel K. Inouye Solar Telescope collected its Science Verification data on 2021 May 7–8. The instrument observed multiple layers of a sunspot atmosphere simultaneously, in passbands of Ca ii 397 nm (H line), Fe i 630 nm, and Ca ii 854 nm, scanning the region with a spatial sampling of 0.″041 and an average temporal cadence of 7.76 s, for a duration of 38.8 minutes. The slit moved southward across the plane of sky at 3.83 km s−1. The spectropolarimetric scans exhibit prominent oscillatory “ridge” structures that lie nearly perpendicular to the direction of slit motion (north to south). These ridges are visible in the maps of line intensity, central wavelength, line width, and both linear and circular polarization. Contemporaneous Atmospheric Imaging Assembly observations indicate that these ridges are purely temporal in character and are likely attributed to the familiar chromospheric 3 minute umbral oscillations. We observe in detail a steady umbral flash near the center of the sunspot umbra. Although bad seeing limited the spatial resolution, the unique high signal-to-noise ratio data enable us to estimate the shock Mach numbers (≈2), propagation speeds (≈9 km s−1), and their impacts on the longitudinal magnetic field (ΔB ≈ 50 G), gas pressure, and temperature (ΔT/T ≈ 0.1) of subshocks over 30 s. We also find evidence for rarefaction waves situated between neighboring wave train shocks. The Ca ii 854 nm line width is fairly steady throughout the umbral flash, except for a sharp 1.5 km s−1 dip immediately before, and a comparable spike immediately after, the passage of the shock front. This zigzag in line width is centered on the subshock and extends over 0.″4.

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The Visible Spectro-Polarimeter of the Daniel K. Inouye Solar Telescope

Cited by 26 publications

References 61 publications

Large aperture optically contacted MgF2 retarders for calibration and modulation at DKIST

Large aperture optically contacted MgF2 retarders for calibration and modulation at DKIST

The Daniel K. Inouye Solar Telescope (DKIST) Cryogenic Near-Infrared Spectro-Polarimeter

First Observation of Chromospheric Waves in a Sunspot by DKIST/ViSP: The Anatomy of an Umbral Flash

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