Abstract
We report on the design and performance of the BICEP2 instrument and on its three-year data set. BICEP2 was designed to measure the polarization of the cosmic microwave background (CMB) on angular scales of 1 to 5 degrees ($\ell$=40-200), near the expected peak of the B-mode polarization signature of primordial gravitational waves from cosmic inflation. Measuring B-modes requires dramatic improvements in sensitivity combined with exquisite control of systematics. The BICEP2 telescope observed from the South Pole with a 26~cm aperture and cold, on-axis, refractive optics. BICEP2 also adopted a new detector design in which beam-defining slot antenna arrays couple to transition-edge sensor (TES) bolometers, all fabricated on a common substrate. The antenna-coupled TES detectors supported scalable fabrication and multiplexed readout that allowed BICEP2 to achieve a high detector count of 500 bolometers at 150 GHz, giving unprecedented sensitivity to B-modes at degree angular scales. After optimization of detector and readout parameters, BICEP2 achieved an instrument noise-equivalent temperature of 15.8 $\mu$K sqrt(s). The full data set reached Stokes Q and U map depths of 87.2 nK in square-degree pixels (5.2 $\mu$K arcmin) over an effective area of 384 square degrees within a 1000 square degree field. These are the deepest CMB polarization maps at degree angular scales to date. The power spectrum analysis presented in a companion paper has resulted in a significant detection of B-mode polarization at degree scales.
Highlights
During the past two decades the ΛCDM model has become the standard framework for understanding the large-scale phenomenology of our universe
We describe the National Institute of Standards and Technology (NIST) SQUIDs and other cold hardware, the room-temperature Multi-Channel Electronics (MCE) system, and the custom control software that were used for data acquisition
We find that the pointing-dependent systematic error on the spectral gain mismatch corresponds to a scatter of 1.7%, so that the Fourier transform spectroscopy (FTS) measurement can only limit the rms spectral mismatch per pair to be below this level
Summary
During the past two decades the ΛCDM model has become the standard framework for understanding the large-scale phenomenology of our universe. The temperature anisotropy measured by the Wilkinson Microwave Anisotropy Probe (WMAP; Hinshaw et al 2013) and Planck (Planck Collaboration et al 2013a) satellites have allowed very precise determination of key parameters such as the mean curvature, the dark energy density, and the baryon fraction In addition to this temperature signal, the CMB possesses a small degree of polarization. The excellent sensitivity and exquisite control of instrumental systematics achieved by Bicep have allowed it to make the first detection of B-mode power on degree angular scales. This analysis is reported in a companion paper, the Results paper (Bicep Collaboration I 2014).
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