The Robinson Gravitational Wave Background Telescope (BICEP): a bolometric large angular scale CMB polarimeter

Abstract

The Robinson Telescope (BICEP) is a ground-based millimeter-wave bolometric array designed to study the polarization of the cosmic microwave background radiation (CMB) and galactic foreground emission. Such measurements probe the energy scale of the inflationary epoch, tighten constraints on cosmological parameters, and verify our current understanding of CMB physics. Robinson consists of a 250-mm aperture refractive telescope that provides an instantaneous field-of-view of 17° with angular resolution of 55´ and 37´ at 100 GHz and 150 GHz, respectively. Fortynine pair of polarization-sensitive bolometers are cooled to 250 mK using a 4 He/ 3 He/ 3 He sorption fridge system, and coupled to incoming radiation via corrugated feed horns. The all-refractive optics is cooled to 4 K to minimize polarization systematics and instrument loading. The fully steerable 3-axis mount is capable of continuous boresight rotation or azimuth scanning at speeds up to 5 deg/s. Robinson has begun its first season of observation at the South Pole. Given the measured performance of the instrument along with the excellent observing environment, Robinson will measure the E-mode polarization with high sensitivity, and probe for the B-modes to unprecedented depths. In this paper we discuss aspects of the instrument design and their scientific motivations, scanning and operational strategies, and the results of initial testing and observations.

BICEP2, Planck, spinorial space-time, pre-Big Bang.

“…The Robinson Telescope [45] is a refractive telescope with a 250-mm aperture providing an instantaneous field-of-view of 17 degrees with angular resolution of 55 arcminutes at 100 GHz and 37 arcminutes at 150 GHz. It was made of fourty-nine pairs of horn-coupled polarization-sensitive bolometers.…”

Mapping speed for an array of corrugated horns

“…These signals are at most a few ×100nK, so observations require high sensitivity and small systematic errors. CMB polarimeters, therefore, have large arrays of receivers coupled to telescopes that are optimized for low scattering [6][7][8]. Existing corrugated horn arrays are relatively sparse, so the horns are designed for maximum aperture efficiency.…”

BICEP2/SPUD: searching for inflation with degree scale polarimetry from the South Pole

“…BICEP1 has been observing the CMB continuously since late February 2006. In June 2006, we published a description of its performance [3], reporting details of calibration, atmospheric noise rejection, optical design and characterization, observing efficiency, and initial temperature and polarization maps. The lessons learned from building, characterizing, and operating BICEP1 guide our program of upgrades.…”

“…[2] The BICEP2/SPUD experiment directly addresses this recommendation. BICEP2/SPUD is designed to be a powerful upgrade of the BICEP1 experiment [3] [4] . BICEP2/SPUD aims to ultimately detect the signature of inflation for r < 0.01, as targeted by the CMB task force.…”