Variable-delay Polarization Modulators for the CLASS Telescopes
Harrington, Kathleen M
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The search for inflationary primordial gravitational waves and the measurement of the optical depth to reionization, both through their imprint on the large angular scale correlations in the polarization of the cosmic microwave background (CMB), has motivated the creation of the Cosmology Large Angular Scale Surveyor (CLASS). CLASS is a four telescope array sited in the Chilean Atacama desert, specifically designed to achieve the sensitivity and stability necessary to observe the CMB large angular scale polarization from the ground. One of the most unique aspects of the CLASS design is a front-end variable-delay polarization modulator (VPM) that uses a wire grid in front of a movable mirror to rapidly modulate the incoming polarization and enable a ``lock-in'' style measurement of polarization from the sky. This thesis covers the design, fabrication, and performance of the VPMs for the CLASS telescopes as well as theoretical modeling of the polarization modulation by the VPM and analysis techniques for the resulting detector timestreams.