UC Berkeley

We present the \pb experiment and its measurement of the B-mode power spectrum. \pb is a millimeter wave telescope that is measuring the Cosmic Microwave Background (CMB) polarization, using large format arrays of photon noise limited Transition-Edge Sensor (TES) bolometers. The instrument observes from the Atacama Desert at 5.2km in elevation with a 2.5m primary aperture telescope. This telescope has sufficient angular resolution (3.5' FWHM) to resolve the gravitational lensing features of the CMB, a new channel for obtaining information on fundamental physics such as the sum of the mass of neutrinos.

This dissertation describes the design, integration and results of the first season of \pb observations. The receiver observed for 1 year with a noise-equivalent temperature (NET) of $22.8\mu K \sqrt{s}$ and mapped a 30 square degree area of the CMB, obtaining evidence for gravitational lensing in the BB power spectrum at a significance of $2\sigma$.