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Title: In Search of Inflation: Tools for Cosmic Microwave Background Polarimetry
Authors: Crowley, Kevin
Advisors: Staggs, Suzanne T.
Contributors: Physics Department
Keywords: Bolometers
Cosmic microwave background
Half-wave plate
Transition-edge sensors
Subjects: Astrophysics
Condensed matter physics
Issue Date: 2018
Publisher: Princeton, NJ : Princeton University
Abstract: The pursuit of knowledge of the early universe via the properties of the cosmic microwave background (CMB) is now being guided by the need to perform measurements of large-scale polarization patterns at a part in 100 million. In addition to confirming the ΛCDM concordance model shaped by the CMB, such studies pursue evidence of primordial tensor perturbations, which themselves could elucidate a period of inflation in the early universe. These tensor perturbations are imprinted on the CMB polarization as divergence-free patterns, known as B-modes. To make these demanding polarization measurements, increased instrumental sensitivity and control of systematics is required. As part of the Advanced ACTPol (AdvACT) project, high-density detector arrays of thousands of highly-sensitive bolometers were deployed on the Atacama Cosmology Telescope (ACT). The Atacama B-mode Search (ABS) instrument featured a polarization modulator system to control systematics and gain access to large-scale anisotropy modes otherwise masked by changing signals in the atmosphere. We describe aspects of these technologies, and their impact on CMB polarization studies. In this thesis, I begin by presenting the standard model of the universe and discuss the promise of CMB polarization measurements. This motivates a discussion of current technologies progressing to an introduction of arrays of multiplexed bolometers. I discuss generic bolometer models involving superconducting thermistors, known as transition-edge sensors (TESes). These models are then compared to data on bolometer sensitivity and response acquired for AdvACT devices. I next describe the principle of polarization modulation using a continuously-rotating half-wave plate (CRHWP), including the signal injected into bolometer data thereby. I present a pipeline developed to investigate and remove this signal. Initial results from the 2017 run of silicon metamaterial CRHWPs on ACT are shown. Finally, I describe the maximum-likelihood pipeline developed as part of the ABS collaboration to constrain the parameter describing the power in primordial tensor perturbations, the tensor-to-scalar ratio r. The final published results for ABS are discussed. I conclude by considering the future development of high-sensitivity focal planes in the context of systematic error control, specifically detector non-linearity, for the Simons Observatory set of instruments, which are in the design phase.
Alternate format: The Mudd Manuscript Library retains one bound copy of each dissertation. Search for these copies in the library's main catalog:
Type of Material: Academic dissertations (Ph.D.)
Language: en
Appears in Collections:Physics

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