MUSCAT: the Mexico-UK Sub-Millimetre Camera for AsTronomy

Abstract

The Mexico-UK Sub-millimetre Camera for AsTronomy (MUSCAT) is a large-format, millimetre-wave camera consisting of 1,500 background-limited lumped-element kinetic inductance detectors (LEKIDs) scheduled for deployment on the Large Millimeter Telescope (Volcán Sierra Negra, Mexico) in 2018. MUSCAT is designed for observing at 1.1 mm and will utilise the full 4 field of view of the LMTs upgraded 50-m primary mirror. In its primary role, MUSCAT is designed for high-resolution follow-up surveys of both galactic and extra-galactic sub-mm sources identified by Herschel. MUSCAT is also designed to be a technology demonstrator that will provide the first on-sky demonstrations of novel design concepts such as horn-coupled LEKID arrays and closed continuous cycle miniature dilution refrigeration.Here we describe some of the key design elements of the MUSCAT instrument such as the novel use of continuous sorption refrigerators and a miniature dilutor for continuous 100-mK cooling of the focal plane, broadband optical coupling to Aluminium LEKID arrays using waveguide chokes and anti-reflection coating materials as well as with the general mechanical and optical design of MUSCAT. We explain how MUSCAT is designed to be simple to upgrade and the possibilities for changing the focal plane unit that allows MUSCAT to act as a demonstrator for other novel technologies such as multi-chroic polarisation sensitive pixels and on-chip spectrometry in the future. Finally, we will report on the current status of MUSCAT's commissioning.He sorption pump each, this is referred to as a He8 cooler (2 × 4 He). The second stage cooled by a CS cooler uses a system where each precooler consists of a 4 He pump and a 3 He pump, referred to as a He14 cooler (2 × [ 4 He+ 3 He]). The operation of these units including how they are cycled in MUSCAT to accommodate large thermal loads, has been described in a previous paper. 4

Early science with the Large Millimeter Telescope: a 1.1 mm AzTEC survey of red-Herschel dusty star-forming galaxies

“…The fast mapping speeds of a new generation of large format cameras for the 50m-LMT (Hughes et al 2020), e.g. MUSCAT (Brien et al 2018) and TolTEC 10 ( Bryan et al 2018), will result in thousands of DSFGs with better photometry and position accuracy for counterpart identification. The angular resolution provided by the 50m primary mirror of the LMT will allow the identification of multiple systems separated by, at least, angular scales 5 arcsec (i.e.…”

Applications for Microwave Kinetic Induction Detectors in Advanced Instrumentation

“…The Large Millimeter Telescope (LMT) Alfonso Serrano, Sierra Negra, Mexico, is the world's largest single aperture telescope for mm wavelengths, and two projects involving MKID cameras are ongoing at the LMT. MUSCAT, the Mexico UK Sub-mm Camera for AsTronomy [44,45] is a collaborative effort to install a 1600 pixels MKID camera at the LMT with a sensitivity band centered around 270 GHz (1.1 mm). MUSCAT uses aluminum MKID pixels that are insensitive to the incoming light's polarization and utilizes a meandering inductor optimized to absorb at the 1.1 mm wavelength.…”

Pre-deployment verification and predicted mapping speed of MUSCAT

“…MUSCAT uses a fully reflective optics train which provides high-quality, diffraction-limited beams in MUS-CAT's 1.1 mm band and also at 850 µm as described in Brien et al 10 In Figure 2 the final two mirrors (M7 and M8) can be seen mounted to the 450 mK plate.…”

“…As mentioned in Section 4.1, we assume a constant opacity of τ = 0.06 during the observation, this lies within the reported interquartile range for the good-weather season at the LMT. 10,15,16 Finally, we assume that all detectors see the same random sky noise.…”