Characterization of the Mid-Frequency Arrays for Advanced ACTPol

TL;DR

This paper details the lab characterization and initial field performance of new mid-frequency detector arrays for Advanced ACTPol, enhancing cosmic microwave background measurements with improved sensitivity and systematic analysis.

Contribution

It presents the first detailed lab characterization and field performance assessment of the 90/150 GHz arrays for Advanced ACTPol, including thermal, optical, and systematic evaluations.

Findings

Arrays show uniform thermal and optical parameters.

Systematic uncertainties are well-characterized.

Initial field performance meets design expectations.

Abstract

The Advanced ACTPol upgrade on the Atacama Cosmology Telescope aims to improve the measurement of the cosmic microwave background anisotropies and polarization, using four new dichroic detector arrays fabricated on 150-mm silicon wafers. These bolometric cameras use AlMn transition-edge sensors, coupled to feedhorns with orthomode transducers for polarization sensitivity. The first deployed camera is sensitive to both 150 GHz and 230 GHz. Here we present the lab characterization of the thermal parameters and optical efficiencies for the two newest fielded arrays, each sensitive to both 90 GHz and 150 GHz. We provide assessments of the parameter uniformity across each array with evaluation of systematic uncertainties. Lastly, we show the arrays' initial performance in the field.