CCAT: Mod-Cam Cryogenic Performance and Its Impact on 280-GHz KID Array Noise

Abstract

The CCAT Observatory’s Fred Young Submillimeter Telescope (FYST) is designed to observe submillimeter astronomical signals with high precision, using receivers fielding state-of-the-art kinetic inductance detector (KID) arrays. Prime-Cam is a first-light, multiband, wide-field camera for FYST, designed to field up to seven instrument modules and provide unprecedented sensitivity across a broad frequency range. Mod-Cam serves as a single-module testbed for Prime-Cam, delivering detailed evaluation of cryogenic behavior prior to deploying modules in Prime-Cam on FYST. We present the cryogenic performance of Mod-Cam in an “optically open” cooldown to validate the testbed, and present detector results from a “cold-load” cooldown to measure the effect of focal-plane temperature stability on detector noise. During the optically open test, we achieved stable base temperatures of $\text{1.5} \,\text{K}$ on the $\text{1} \,\text{K}$ stage and $\text{85} \,\text{m}\text{K}$ at the detector stage. In the cold-load configuration, we measured a detector focal-plane root-mean-square temperature stability of $\text{3.2} \times \text{10}^{-\text{5}} \,\text{K}$. From this stability measurement, we demonstrate that the equivalent power from focal-plane thermal fluctuations is only 0.0040% of a $\text{5} \,\text{p}\text{W}$ incident photon power for aluminum detectors and 0.0023% for titanium-nitride detectors, a negligible level for CCAT science goals. This highlights the success of the cryogenic system design and thermal management.