Large Millimeter Bolometric Arrays on ACT for Cosmic Microwave Background Observations

Abstract

Two upgraded cameras on the Atacama Cosmology Telescope (ACT), the ACT Polarimeter (ACTPol) and the Advanced ACTPol, have made and will make measurements of the temperature and polarization in the Cosmic Microwave Background (CMB) with arcminute resolution. The ACT observing site is located 5200 m near the top of Cerro Toco in the Atacama Desert of northern Chile. This thesis work

is based on my efforts on ACTPol and Advanced ACTPol since 2013 and presents research with the polarimeters employed to map the CMB sky with the ACT’s focal plane arrays at multiple frequency bands.

In the Chapter 1, the Cosmic Microwave Background is reviewed and an introduction of current CMB telescopes with a concentration on ground based systems currently located in Chile and at the South Pole is presented. Also, an overview of ACT telescope is

detailed, on the site, the instrument and the scan strategy. Chapter 2 describes the bolometer physics and properties of the ACTPol’s and the Advanced ACTPol’s detectors. Chapter 3 describes the implementation of the multiplexing readout systems

for these two cameras and the readout assembly schematics. Chapter 4 describes the work on the assembly of the detector array, which details all the procedures to put together the array package. It includes the work on the assembly of the ACTPol’s second

and third arrays as well as the first three arrays of the Advanced ACTPol. Thus this section compares the similarity and difference between two generations of the cameras; and also presents the challenges moving toward high-density arrays. Chapter

5 summarizes the analysis which characterizes the ACT detector performance in the lab and in-situ. By the time of this dissertation, there have been six cameras on the ACT telescope, the analysis covers the characterization of these cameras individually

or in ensemble for better systematics understanding. Chapter 6 concludes this thesis work with future prospects.