BICEP1 is a small aperture refractive telescope which provides an instantaneous field of view of 17 degrees with an angular resolution of 55' and 37' at 100 GHz and 150 GHz respectively. 49 pairs of polarization-sensitive bolometers are cooled to 250 mK using a He4/He3 sorption fridge, and are coupled to incoming radiation via corrugated feed horns. The refractive optics are cooled to 4K to minimize loading and systematics.
Left: Cutaway view of the BICEP1 cryostat with optics shown. Right: The 4K insert
surrounds the 250mK focal plane. For simplicity only one pixel's horn is shown.
Left: The fully assembled focal plane. Right: The measured beams.
From 2006-2008, BICEP1 observed a ~1000 square degree region which is expected to have
low foreground contamination. BICEP1 currently holds the best upper limit r derived from
a search for B-mode polarization of r<0.72 at 95% CL (Chiang et al. 2010).