In situ Performance of the Low Frequency Arrayfor Advanced ACTPol

TL;DR

This paper reports on the initial in situ performance characterization of the Low Frequency Array of the Advanced ACTPol, which uses TES detectors at 27 and 39 GHz to observe the CMB and galactic signals.

Contribution

It provides the first on-site performance metrics of the LF array, including time constant, optical efficiency, and sensitivity, for the AdvACT project.

Findings

Array sensitivity measurements obtained

Optical efficiency characterized

Time constant assessed

Abstract

The Advanced Atacama Cosmology Telescope Polarimeter (AdvACT) \cite{thornton} is an upgrade for the Atacama Cosmology Telescope using Transition Edge Sensor (TES) detector arrays to measure cosmic microwave background (CMB) temperature and polarization anisotropies in multiple frequencies. The low frequency (LF) array was deployed early 2020. It consists of 292 TES bolometers observing in two bands centered at 27 GHz and 39 GHz. At these frequencies, it is sensitive to synchrotron radiation from our galaxy as well as to the CMB, and complements the AdvACT arrays operating at 90, 150 and 230 GHz. We present the initial LF array on-site characterization, including the time constant, optical efficiency and array sensitivity.