The kinetic inductance detectors for the MISTRAL instrument: Installation and characterization at the Sardinia Radio Telescope

Abstract

The MISTRAL instrument, a cryogenic W-band camera equipped with 415 lumped element kinetic inductance detectors, achieved a significant milestone in May 2023 with its successful installation at the Gregorian focus of the Sardinia Radio Telescope, a 64 m aperture telescope in Italy. MISTRAL features a focal plane of approximately 94.4 mm in diameter, providing an instantaneous field of view of about 4 arcmin. To maintain the telescope’s angular resolution of $\sim \text{12}\text{arcsec}$, the focal plane has been over-sampled with pixels separated by 4.2 mm, meaning a pixel separation of approximately 10.6 arcsec. The lumped element kinetic inductance detectors in MISTRAL are made of a titanium–aluminum bilayer, $10+\text{30}\text{nm}$ thick, on a 100 mm-diameter Silicon wafer, 235 µm thick. The detectors are designed to have 415 resonances over a $\sim \text{500}\text{MHz}$ bandwidth, to work in a temperature range of 200 to 240 mK, and to be sensitive in the W-band. In this contribution, we present the preliminary characterization of the MISTRAL detectors at the Sardinia Radio Telescope, comparing their performance to measurements conducted in the laboratory.