Mapping the Polarized Microwave Sky with ACTPol
ACTPol is a novel polarization-sensitive receiver for the Atacama Cosmology Telescope (ACT) designed to measure the Cosmic Microwave Background (CMB) anisotropies to high precision on a wide range of angular scales. The instrument features three optically-independent feedhorn-coupled transition-edge sensor (TES) bolometer arrays continuously cooled below 100 mK with the aid of a dilution refrigerator. The first two arrays, each composed of 512 single-frequency polarimeters sensitive to 150 GHz, were deployed sequentially during the 2013 and 2014 observing seasons. A third, 256-polarimeter dichroic array operating at both 90 and 150 GHz was added in early 2015. I will present an overview of the experiment and discuss some of the challenges associated with converting raw data into accurate, high-resolution maps of the CMB. I will also highlight some early scientific results and report on the status of ongoing analyses.