CAPMAP: A New Instrument to Measure the E-mode CMB Polarization on Angular Scales of 4 arcmin to 40 arcmin

TL;DR

CAPMAP is an advanced instrument designed to measure the E-mode polarization of the CMB at small angular scales, aiming to confirm standard cosmological models through precise polarization data.

Contribution

This paper introduces a new 90 GHz array of correlation polarimeters specifically built to measure the CMB E-mode polarization at high angular resolution.

Findings

Instrument is sensitive enough to detect micro Kelvin polarization signals.

Field observations confirm instrument calibration and beam characterization.

Preliminary data shows potential for successful polarization detection.

Abstract

The CMB polarization is the Everest in the quest to characterize the earliest photons from the Universe. After a long list of ever-decreasing upper limits, a detection of polarization was made in 2002 by the DASI team at ell =~ 500. The experiment described in this thesis is designed to make a more detailed measurements at higher angular resolution. The E-mode polarization power spectrum not only provides a more direct link to the properties of the last scattering surface than the temperature anisotropy but also offers complementary information which can be used to break various degeneracies in the determination of cosmological parameters. Most importantly, the existence of polarization is a robust prediction of the standard cosmological picture so a precise measurement of the CMB polarization should come as a confirmation of the standard model. However, polarization measurements represent an experimental challenge. The weakness of the polarization signal requires both a demanding instrumental sensitivity and focused attention to all sources of systematic error. This thesis describes the design, construction, and testing of a 90 GHz four-element array of correlation polarimeters to probe the E-mode polarization power spectrum at multipoles (ell) ranging from 500 to 1500. The array was fielded in Jan 2003 on the 7-meter Crawford Hill antenna, in Holmdel, New Jersey and observed for two months. The receiver calibration is described in detail, as well as the characterization of the pointing and beams. Preliminary analysis indicates that the instrument is sufficiently sensitive to detect the few micro Kelvin signal of the CMB polarization.