Prime-Cam, a first-generation science instrument for the Atacama-based Fred Young Submillimeter Telescope, is being built by the CCAT Collaboration to observe at millimeter and submillimeter wavelengths using kinetic inductance detectors (KIDs). Prime-Cam’s 280 GHz instrument module will deploy with two aluminum-based KID arrays and one titanium nitride-based KID array, totaling ∼10,000 detectors at the focal plane, all of which have been fabricated and are currently undergoing testing. One complication of fielding large arrays of KIDs under dynamic loading conditions is tuning the detector tone powers to maximize signal-to-noise while avoiding bifurcation due to the nonlinear kinetic inductance. For aluminum-based KIDs, this is further complicated by additional nonlinear effects which couple tone power to resonator quality factors and resonant frequencies. While both nonequilibrium quasiparticle dynamics and two-level system fluctuations have been shown to give rise to qualitatively similar distortions, modeling these effects alongside nonlinear kinetic inductance is inefficient when fitting thousands of resonators on-sky with existing models. For this reason, it is necessary to have a detailed understanding of the nonlinear effects across relevant detector loading conditions, including how they impact on on-sky noise and how to diagnose the detector’s relative performance. We present a study of the competing nonlinearities seen in Prime-Cam’s 280 GHz aluminum KIDs, with a particular emphasis on the resulting distortions to the resonator line shape and how these impact detector parameter estimation.
Prime-Cam is a first-generation science instrument for the CCAT Observatory’s six-meter aperture Fred Young Submillimeter Telescope (FYST). FYST’s crossed-Dragone design provides high optical throughput to take advantage of its unique site at 5600 m on Cerro Chajnantor in Chile’s Atacama Desert to reach mapping speeds over ten times greater than current and near-term submillimeter experiments. Housing up to seven independent instrument modules in its 1.8-meter diameter cryostat, Prime-Cam will combine broadband polarization-sensitive modules and spectrometer modules designed for observations in several frequency windows between 210 GHz and 850 GHz to study a wide range of astrophysical questions from Big Bang cosmology to the formation of stars and galaxies in the Epoch of Reionization and beyond. In order to cover this range of frequencies and observation modes, each of the modules contains a set of cold reimaging optics that is optimized for the science goals of that module. These optical setups include several filters, three or four anti-reflection-coated silicon lenses, and a Lyot stop to control the field of view and illumination of the primary mirror, satisfy a series of mechanical constraints, and maximize optical performance within each passband. We summarize the design considerations and trade-offs for the optics in these modules and provide a status update on the fabrication of the Prime-Cam receiver and the design of its 1 K and 100 mK thermal BUSs.
KEYWORDS: Sensors, Resonators, Detector arrays, Data acquisition, Signal attenuation, Equipment, Quantum reading, Calibration, Signal processing, Signal detection
We outline the development of the readout software for the Prime-Cam and Mod-Cam instruments on the CCAT Fred Young Submillimeter Telescope (FYST), primecam readout. The instruments feature Lumped-element Kinetic Inductance Detector (LEKID) arrays driven by Xilinx ZCU111 RFSoC boards. In the current configuration, each board can drive up to 4000 KIDs, and Prime-Cam is implementing approximately 25 boards. The software runs on a centralized control computer connected to the boards via dedicated ethernet and facilitates such tasks as frequency-multiplexed tone comb driving, comb calibration and optimization, and detector timestream establishment. The control computer utilizes dynamically generated control channels for each board, allowing for simultaneous parallel control overall, while uniquely tracking diagnostics for each. This work demonstrates a scalable RFSoC readout architecture where computational demands increase linearly with the number of detectors, enabling control of tens-of-thousands of KIDs with modest hardware, and opening the door to the next generation of KID arrays housing millions of detectors.
The epoch of reionization spectrometer (EoR-Spec) is an instrument module that will be deployed in the Prime-Cam receiver on the Fred Young Submillimeter Telescope (FYST), which is a 6m off-axis telescope for the CCAT-prime facility. FYST is currently being built in the Atacama Desert in Chile at an altitude of 5600 m. With the Fabry-Perot interferometer (FPI), EoR-Spec will measure the 158 µm [CII] line intensity at redshifts from 3.5 to 8 (420 to 210 GHz), with the lower redshifts tracing star formation and higher redshifts tracing the late stages of reionization. An EoR-Spec module includes three monolithic and monochroic feedhorn-coupled arrays of kinetic inductance detectors (KIDs), two of which are centered at 260 GHz with the other centered at 370 GHz. We present the design and integration process of the EoR-Spec detector array at both bands. The 370 GHz detector array will consist of 3072 detectors and each of the 260 GHz arrays will consist of 1728 detectors. Each of the detector arrays contains an aluminum feedhorn array and is read out by a few pairs of coaxial cables.
The Epoch of Reionization Spectrometer (EoR-Spec) will be an instrument module for the Prime-Cam receiver on the CCAT-prime Collaboration’s Fred Young Submillimeter Telescope (FYST), a 6-m primary mirror Crossed Dragone telescope. With its Fabry-Perot interferometer (FPI), EoR-Spec will step through frequencies between 210 and 420 GHz to perform line intensity mapping of the 158 µm [CII] line in aggregates of star-forming galaxies between redshifts of 3.5 and 8 to trace the evolution of structure in the Universe during the epoch of reionization. Here we present the optical design of the module including studies of the optical quality and other key parameters at the image surface. In order to achieve the optimal resolving power (R∼100) with the FPI, it is important to have a highly collimated beam at the Lyot stop of the system; the optimization process to achieve this goal with four lenses instead of three as used in other Prime-Cam modules is outlined. As part of the optimization, we test the effect of replacing some of the aspheric lenses with biconic lenses in this Crossed Dragone design and find that the biconic lenses tends to improve the image quality across the focal plane of the module.
Mod-Cam is a first light and commissioning instrument for the CCAT-prime project’s six-meter aperture Fred Young Submillimeter Telescope (FYST), currently under construction at 5600 m on Cerro Chajnantor in Chile’s Atacama Desert. Prime-Cam, a first-generation science instrument for FYST, will deliver over ten times greater mapping speed than current and near-term facilities for unprecedented 280–850 GHz broadband and spectroscopic measurements with microwave kinetic inductance detectors (MKIDs). CCAT-prime will address a suite of science goals, from Big Bang cosmology to star formation and galaxy evolution over cosmic time. Mod-Cam deployment on FYST with a 280 GHz instrument module containing MKID arrays is planned for early science observations in 2024. Mod-Cam will be used to test instrument modules for Prime-Cam, which can house up to seven instrument modules. We discuss the design and status of the 0.9 m diameter, 1.8 m long Mod-Cam receiver and 40 cm diameter 280 GHz instrument module, with cold stages at 40 K, 4 K, 1 K, and 100 mK. We also describe the instrument module’s cryogenic readout designs to enable the readout of more than 10,000 MKIDs across 18 networks.
Prime-Cam is a first-generation instrument for the Cerro Chajnantor Atacama Telescope-prime (CCAT-prime) Facility. The 850 GHz module for Prime-Cam will probe the highest frequency of all the instrument modules. We describe the parameter space of the 850 GHz optical system between the Fλ spacing, beam size, pixel sensitivity, and detector count. We present the optimization of an optical design for the 850 GHz instrument module for CCAT-prime. We further describe the development of the cryogenic RF chain design to accommodate 30 readout lines to read 41,400 kinetic inductance detectors (KIDs) within the cryogenic testbed.
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