Design and Deployment of a Multichroic Polarimeter Array on the Atacama Cosmology Telescope

TL;DR

This paper details the design, deployment, and initial performance of a pioneering multichroic polarimeter array on the Atacama Cosmology Telescope, enabling simultaneous observations in multiple CMB frequency bands.

Contribution

It introduces the first multichroic detector array used in a CMB experiment, combining broadband optics and novel anti-reflection coatings for enhanced observational capabilities.

Findings

Successful deployment and initial performance validation on sky

Effective multichroic detection in 90 and 146 GHz bands

Paves the way for future multichroic CMB instruments

Abstract

We present the design and the preliminary on sky performance with respect to beams and pass-bands of a multichroic polarimeter array covering the 90 and 146 GHz Cosmic Microwave Background (CMB) bands and its enabling broadband optical system recently deployed on the Atacama Cosmology Telescope (ACT). The constituent pixels are feedhorn-coupled multichroic polarimeters fabricated at NIST. This array is coupled to the ACT telescope via a set of three silicon lenses incorporating novel broad-band metamaterial anti-reflection coatings. This receiver represents the first multichroic detector array deployed for a CMB experiment and paves the way for the extensive use of multichroic detectors and broadband optical systems in the next generation of CMB experiments.