The Simons Observatory 220 and 280 GHz Focal-Plane Module: Design and Initial Characterization

TL;DR

This paper details the design and initial testing of the 220/280 GHz focal-plane modules for the Simons Observatory, highlighting detector performance and system integration for cosmological observations.

Contribution

It introduces the design and initial characterization results of the 220/280 GHz detector modules, a key component for the observatory's multi-frequency sky mapping.

Findings

Detector yield is high for the 220/280 GHz modules.

Readout noise levels are within expected ranges.

Modules demonstrate robust heat-sinking and electromagnetic shielding.

Abstract

The Simons Observatory (SO) will detect and map the temperature and polarization of the millimeter-wavelength sky from Cerro Toco, Chile across a range of angular scales, providing rich data sets for cosmological and astrophysical analysis. The SO focal planes will be tiled with compact hexagonal packages, called Universal Focal-plane Modules (UFMs), in which the transition-edge sensor (TES) detectors are coupled to 100 mK microwave-multiplexing electronics. Three different types of dichroic TES detector arrays with bands centered at 30/40, 90/150, and 220/280 GHz will be implemented across the 49 planned UFMs. The 90/150GHz and 220/280 GHz arrays each contain 1,764 TESes, which are read out with two 910x multiplexer circuits. The modules contain a series of densely routed silicon chips, which are packaged together in a controlled electromagnetic environment with robust heat-sinking to 100 mK. Following an overview of the module design, we report on early results from the first 220/280GHz UFM, including detector yield, as well as readout and detector noise levels.