Abstract:
The solar physics community is entering a golden era that is ripe with next-generation
ground- and space-based facilities, advanced spectral inversion techniques, and realistic
simulations that are becoming more computationally streamlined and efficient. With ever increasing resolving power stemming from the newest observational telescopes, it becomes
more challenging to obtain (near-)simultaneous measurements at high spatial, temporal and
spectral resolutions, while operating at the diffraction limit of these new facilities. Hence,
in recent years there has been increased interest in the capabilities integral field units (IFUs)
offer towards obtaining the trifecta of high spatial, temporal and spectral resolutions contem poraneously. To date, IFUs developed for solar physics research have focused on mid-optical
and infrared measurements. Here, we present an IFU prototype that has been designed for
operation within the near-ultraviolet to mid-optical wavelength range, which enables key
spectral lines (e.g., Ca II H/K, Hβ, Sr II, Na I D1/D2, etc.) to be studied, hence provid ing additional spectral coverage to the instrument suites developed to date. The IFU was
constructed as a low-budget proof-of-concept for the upcoming 2 m class Indian National
Large Solar Telescope and employs circular cross-section fibres to guide light into a Czerny–
Turner configuration spectrograph, with the resulting spectra captured using a high quantum
efficiency scientific CMOS camera. Mapping of each input fibre allows for the reconstruc tion of two-dimensional spectral images, with frame rates exceeding 20 s−1 possible while
operating in a non-polarimetric configuration. Initial commissioning of the instrument was
performed at the Dunn Solar Telescope, USA, during August 2022. The science verification
data presented here highlights the suitability of fibre-fed IFUs operating at near-ultraviolet
wavelengths for solar physics research. Importantly, the successful demonstration of this
type of instrument paves the way for further technological developments to make a future
variant suitable for upcoming ground-based and space-borne telescope facilities.
