Abstract
We present the design, manufacturing, and testing of a 37-element array of corrugated feedhorns for Cosmic Microwave Background CMB) measurements between 140 and 170 GHz. The array was designed to be coupled to Kinetic Inductance Detector arrays, either directly (for total power measurements) or through an orthomode transducer (for polarization measurements). We manufactured the array in platelets by chemically etching aluminum plates of 0.3 mm and 0.4 mm thickness. The process is fast, low-cost, scalable, and yields high-performance antennas compared to other techniques in the same frequency range. Room temperature electromagnetic measurements show excellent repeatability with an average cross polarization level about − 20 dB, return loss about − 25 dB, first sidelobes below − 25 dB and far sidelobes below − 35 dB. Our results qualify this process as a valid candidate for state-of-the-art CMB experiments, where large detector arrays with high sensitivity and polarization purity are of paramount importance in the quest for the discovery of CMB polarization B-modes.
Highlights
The Cosmic Microwave Background (CMB) is one of the most powerful probes that allows us to study the early Universe and constrain cosmological parameters to Extended author information available on the last page of the article.Experimental Astronomy (2021) 51:249–272 sub-per-cent precision [1]
We present the design, manufacturing, and testing of a 37-element array of corrugated feedhorns for Cosmic Microwave Background CMB) measurements between 140 and 170 GHz
Room temperature electromagnetic measurements show excellent repeatability with an average cross polarization level about −20 dB, return loss about −25 dB, first sidelobes below −25 dB and far sidelobes below −35 dB. Our results qualify this process as a valid candidate for state-of-the-art CMB experiments, where large detector arrays with high sensitivity and polarization purity are of paramount importance in the quest for the discovery of CMB polarization B-modes
Summary
The Cosmic Microwave Background (CMB) is one of the most powerful probes that allows us to study the early Universe and constrain cosmological parameters to. When the plasma temperature fell below ∼ 3 000 K, matter became neutral and radiation decoupled, propagating freely in the expanding universe Today, we detect this radiation as a black-body emission at ∼ 2.73 K, with a brightness peak at ∼ 160 GHz. The CMB intensity anisotropies, T /T ∼ 10−5, trace the primordial density fluctuations, while polarization anisotropies, P /P ∼ 10−6, were generated at the last scattering surface by variations both in the matter density (scalar fluctuations) and in the gravitational field (tensor fluctuations). In this paper we address this challenge and propose chemical-etching combined with the so-called platelet technique to build high-performance arrays of corrugated feedhorns in the D-band (110-170 GHz) with very low-cost and processing time. We discuss possible ways to improve the achieved performance
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