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The MIllimeter Sardinia radio Telescope Receiver based on Array of Lumped elements KIDs, MISTRAL, is a cryogenic LEKID camera, operating in the W band ( 77 - 103 GHz ) from the Gregorian focus of the 64-m aperture Sardinia Radio Telescope (SRT), in Italy. This instrument features a high angular resolution ( ∼ 12 arcsec ) and a wide instantaneous field of view ( ∼ 4 arcmin ), allowing continuum surveys of the mm-wave sky with many scientific targets, including observations of galaxy clusters via the Sunyaev–Zel'dovich effect. In May 2023, MISTRAL has been installed at SRT for the technical commissioning. In this contribution, we will describe the MISTRAL instrument focusing on the laboratory characterization of its focal plane: a ∼ 400 -pixel LEKID array. We will show the optical performance of the detectors highlighting the procedure for the identification of the pixels on the focal plane, the measurements of the optical responsivity and NEP, and the estimation of the optical efficiency. [ABSTRACT FROM AUTHOR]

Large radio and mm–wave telescopes use very sensitive detectors requiring cryogenic cooling to reduce detector noise. Pulse Tubes (PT) cryocoolers are widely used to reach temperatures of a few K, defining the base temperature of further sub–K stages. This technology represents an effective solution for continuous operation, featuring high stability and reduced vibration levels on the detectors. However, the compressor used to operate the PT is a significant source of microphonics and electrical noise, making its use at the focus of large steerable telescopes not advisable. This calls for long flexible helium lines between the compressor, operated at the base of the radio telescope, and the cold–head, mounted in the receivers cabin with the receiver detectors. The distance between the receiver cabin and the base can be >100 m long for large radio telescopes. In the framework of our development of the MIllimetric Sardinia radio Telescope Receiver based on Array of Lumped elements kids (MISTRAL), a W–band camera working at the Gregorian focus of the 64 m aperture Sardinia Radio Telescope (SRT) with an array of Lumped Elements Kinetic Inductance Detectors (LEKID), we have developed a cryogenic system based on a PT refrigerator as the first cooling stage. Here we describe the MISTRAL cryogenic system and focus on the validation of the use of a commercial PT Cryocooler with 100 m helium lines running from the cold head to the compressor unit. The configuration allows us to operate the 0.9 W PT reaching below 4.2 K with 0.5 W dissipation. [ABSTRACT FROM AUTHOR]

The MIllimetric Sardinia radio Telescope Receiver based on Array of Lumped elements KIDs, MISTRAL, is a cryogenic W-band (77–103 GH) LEKID camera which will be integrated at the Gregorian focus of the 64 m aperture Sardinia Radio Telescope, in Italy, in Autumn 2022. This instrument, thanks to its high angular resolution ( ∼ 13 arcsec ) and the wide instantaneous field of view ( ∼ 4 arcmin ), will allow continuum surveys of the mm-wave sky with a variety of scientific targets, spanning from extragalactic astrophysics to solar system science. In this contribution, we will describe the design of the MISTRAL camera, with a particular focus on the optimisation and test of a prototype of the focal plane. [ABSTRACT FROM AUTHOR]