We present a new, fully-funded ground-based instrument designed to measure
the B-mode polarization of the Cosmic Microwave Background (CMB). The concept
is based on three independent sub-systems operating at 90, 150 and 220 GHz,
each comprising a telescope and a focal plane of horn-coupled background-limited bolometers. This highly-sensitive experiment, planned to be based at Dome C station in Antarctica, is optimised to produce very low systematic
effects. It will allow the detection of the CMB polarization over angular multipoles 20<l<1000
accurately enough to measure the B-mode signature from gravitational
waves to a lensing-confusion-limited tensor-to-scalar ratio r ~ 0.005.