The Design of the CCAT-prime Epoch of Reionization Spectrometer Instrument

The epoch of reionization spectrometer (EoR-Spec) is an instrument module for the Prime-Cam receiver of the 6-m aperture CCAT-prime Telescope at 5600 m in Chile. EoR-Spec will perform 158 $$\upmu $$m [CII] line intensity mapping of star-forming regions at redshifts between 3.5 and 8 (420–210 GHz), tracing the evolution of structure during early galaxy formation. At lower redshifts, EoR-Spec will observe galaxies near the period of peak star formation—when most stars in today’s universe were formed. At higher redshifts, EoR-Spec will trace the late stages of reionization, the early stages of galaxy assembly, and the formation of large-scale, three-dimensional clustering of star-forming galaxies. To achieve its science goals, EoR-Spec will utilize CCAT-prime’s exceptionally low water vapor site, large field of view ($$\sim 5^\circ $$ at 210 GHz), and narrow beam widths ($$\sim 1$$ arcminute at 210 GHz). EoR-Spec will be outfitted with a cryogenic, metamaterial, silicon substrate-based Fabry–Perot interferometer operating at a resolving power ($$\lambda /\varDelta \lambda $$) of 100. Monolithic dichroic arrays of cryogenic, feedhorn-coupled transition edge sensor bolometers provide approximately 6000 detectors, which are read out using a frequency division multiplexing system based on microwave SQUIDs. The novel design allows the measurement of the [CII] line at two redshifts simultaneously using dichroic pixels and two orders of the Fabry–Perot. Here we present the design and science goals of EoR-Spec, with emphasis on the spectrometer, detector array, and readout designs.