Design and Performance of Kilo-Pixel TES Arrays for ACTPol

ACTPol, a polarization sensitive receiver for the Atacama Cosmology Telescope, is designed to make sensitive maps of the cosmic microwave background anisotropies at arcminute scales and millimeter wavelengths by employing three arrays of superconducting transition edge sensor (TES) detectors. The ACTPol TES bolometers have a target superconducting transition temperature of 150 mK and will be cooled to a bath temperature of 100 mK with a dilution refrigerator enabling increased array sensitivity. Each array will consist of ~1000 TES detectors coupled to a micromachined silicon feedhorn stack via superconducting ortho-mode transducers and transmission lines. The superconducting detectors of the first ACTPol array have been characterized in their final receiver configuration with measurements of key TES parameters including the transition temperature, saturation power, and thermal conductance.