Characterization of AlMn TES Impedance, Noise, and Optical Efficiency in the First 150 mm Multichroic Array for Advanced ACTPol

Abstract

The Advanced ACTPol (AdvACT) upgrade to the Atacama Cosmology Telescope features large arrays of multichroic pixels consisting of two orthogonal-polarization pairs of superconducting bolometers at two observing frequency bands. We present measurements of the detector properties and noise data in a subset of a fielded multichroic array of AlMn transition-edge sensor (TES) detectors. In this array, the distribution of critical temperature T-c across detectors appears uniform at the percent level. The measured noise-equivalent power (NEP) distributions over similar to 1200 detectors are consistent with expectations. We find median NEPs of 4.0x10(-17) W/root Hz for low-band detectors and 6.2x10(-17) W/root Hz for high-band detectors under covered-window telescope test conditions with optical loading comparable to observing with precipitable water vapor similar to 0.5 mm. Lastly, we show the estimated detector optical efficiency, and demonstrate the ability to perform optical characterization over hundreds of detectors at once using a cryogenic blackbody source.