Measuring the Polarization of the Cosmic Microwave Background with BICEP3

• Main Author: Hui, Howard
• Format: Thesis
• Language: English
• Published: 2018
• Subjects: Amundsen Scott South Pole Station; Amundsen-Scott; Amundsen-Scott South Pole Station; South Pole; South pole
• Online Access: https://thesis.library.caltech.edu/11014/; https://thesis.library.caltech.edu/11014/7/Hui_Howard_2018_2.pdf; https://resolver.caltech.edu/CaltechTHESIS:06042018-002455152

Inflation, a period of accelerated expansion in the early Universe, is postulated to answer the horizon, flatness and monopole problems in the standard model of the Universe. This inflationary scenario generically predicts the existence of primordial gravitational waves, which would leave an unique B-mode polarization pattern in the Cosmic Microwave Background. Detection of the primordial B modes at degree angular scales would be a direct evidence for inflation; and the amplitude, parametrized by the tensor-to-scalar ratio r, would allow us to probe the energy scale at 10 -35 second after the Big Bang. The Bicep/Keck Array experiment is a series of telescopes located at the Amundsen-Scott South Pole Station designed to measure the CMB polarization at degree angular scales. The latest result in Bicep/Keck Array, using data collected up to 2015, and combined with other external data, set upper limits on r < 0.06 at 95% confidence. Bicep3 is the latest addition in the experiment, deployed to South Pole in 2015, and started science observation in 2016. It is a 520 mm aperture, compact two-lens refracting telescope at 95 GHz. With 2500 detectors, it achieved instantaneous sensitivity of 9.1μK√s and 7.3μK√s for 2016 and 2017, respectively. After two year of observations, Bicep3 is estimated to reach a map depth of 3.8μK-arcmin. This is the most sensitive polarization measurement at 95 GHz to date. This dissertation provides an overview of the Bicep3 instrument design. In particular, the performance of the sub-Kelvin focal plane structure, antenna-coupled transition edge sensor and time domain multiplexing SQUID readout system. We discuss various calibration methods used to probe instrument sensitivity and systematics. Finally, we review the analysis pipeline, and some preliminary results from Bicep3.