Characterization of the Mid-Frequency Arrays for Advanced ACTPol

Abstract

The Advanced ACTPol upgrade on the Atacama Cosmology Telescope aims to improve the measurement of the cosmic microwave background anisotropies and polariza- tion, using four new dichroic detector arrays fabricated on 150-mm silicon wafers. These bolometric cameras use AlMn transition-edge sensors, coupled to feedhorns with ortho- mode 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.