Observations of the temperature anisotropy of the Cosmic Microwave Background ( CMB ) lend support to an inflationary origin of the universe , yet no direct evidence verifying inflation exists .
Many current experiments are focussing on the CMB ’ s polarization anisotropy , specifically its curl component ( called “ B-mode ” polarization ) , which remains undetected .
The inflationary paradigm predicts the existence of a primordial gravitational wave background that imprints a unique B-mode signature on the CMB ’ s polarization at large angular scales .
The CMB B-mode signal also encodes gravitational lensing information at smaller angular scales , bearing the imprint of cosmological large scale structures ( LSS ) which in turn may elucidate the properties of cosmological neutrinos .
The quest for detection of these signals ; each of which is orders of magnitude smaller than the CMB temperature anisotropy signal , has motivated the development of background-limited detectors with precise control of systematic effects .
The POLARBEAR experiment is designed to perform a deep search for the signature of gravitational waves from inflation and to characterize lensing of the CMB by LSS .
POLARBEAR is a 3.5 meter ground-based telescope with 3.8 arcminute angular resolution at 150 GHz .
At the heart of the POLARBEAR receiver is an array featuring 1274 antenna-coupled superconducting transition edge sensor ( TES ) bolometers cooled to 0.25 Kelvin .
POLARBEAR is designed to reach a tensor-to-scalar ratio of 0.025 after two years of observation – more than an order of magnitude improvement over the current best results , which would test physics at energies near the GUT scale .
POLARBEAR had an engineering run in the Inyo Mountains of Eastern California in 2010 and will begin observations in the Atacama Desert in Chile in 2011 .