UC Berkeley

Modern observations of the cosmic microwave background (CMB) are focused on measuring its primordial ``B-mode" component, a polarization pattern imprinted onto the CMB by gravitational waves during a postulated era of cosmological inflation. A discovery of this signal in the CMB power spectra is concrete evidence of the existence of an inflationary period, and has become the most sought-after measurement in the field. However, this signal is extremely faint and thus difficult to measure, motivating CMB polarization experiments to maximize their sensitivity through both hardware and software advancements. As instrumental sensitivity improves, previously unknown systematics reveal themselves, bottlenecking the overall sensitivity. This dissertation focuses on mitigating one such effect, the E to B mixing caused by time-ordered data (TOD) filtering.

This dissertation is structured as follows. Chapter 1 reviews the relevant cosmology theory that motivates the search for primordial B-modes. Chapter 2 describes the Simons Array experiment and its major hardware systems, most notably the development of the cryogenic half-wave plate. Chapter 3 gives an overview of the filter-bin mapmaking style of ground-based CMB data analysis pipelines, as well as noteworthy features of Simons Array offline software. Chapter 4 introduces a modified method of destriping mapmaking in which satellite data is used to regularize the ground-based data, avoiding the issue of degeneracies for unbiased mapmaking in ground-based experiments. Chapter 5 discusses a novel implementation of E/B separation of filtered TODs in map-space, targeting a particularly important source of sensitivity loss for ground-based experiments.