MUSCAT focal plane verification

TL;DR

This paper presents the laboratory characterization of the MUSCAT focal plane, a large-format submillimetre camera with 1458 LEKID detectors, including resonance, noise, beam, responsivity, and spectral response measurements.

Contribution

It provides the first comprehensive laboratory characterization of the MUSCAT focal plane, demonstrating detector performance and spectral properties.

Findings

Detectors have a mean FWHM of ~3.27 mm, close to the expected 3.1 mm.

Most detectors are photon noise limited under 300 K optical load.

Spectral response confirms a bandwidth of 1.0--1.2 mm centered on 1.1 mm.

Abstract

The Mexico-UK Submillimetre Camera for Astronomy (MUSCAT) is the second-generation large-format continuum camera operating in the 1.1 mm band to be installed on the 50-m diameter Large Millimeter Telescope (LMT) in Mexico. The focal plane of the instrument is made up of 1458 horn coupled lumped-element kinetic inductance detectors (LEKID) divided equally into six channels deposited on three silicon wafers. Here we present the preliminary results of the complete characterisation in the laboratory of the MUSCAT focal plane. Through the instrument's readout system, we perform frequency sweeps of the array to identify the resonance frequencies, and continuous timestream acquisitions to measure and characterise the intrinsic noise and 1/f knee of the detectors. Subsequently, with a re-imaging lens and a black body point source, the beams of every detector are mapped, obtaining a mean FWHM size of $\sim$3.27 mm, close to the expected 3.1 mm. Then, by varying the intensity of a beam filling black body source, we measure the responsivity and noise power spectral density (PSD) for each detector under an optical load of 300 K, obtaining the noise equivalent power (NEP), with which we verify that the majority of the detectors are photon noise limited. Finally, using a Fourier Transform Spectrometer (FTS), we measure the spectral response of the instrument, which indicate a bandwidth of 1.0--1.2 mm centred on 1.1 mm, as expected.