The Keck Array: a pulse tube cooled CMB polarimeter
  The Keck Array is a cosmic microwave background (CMB) polarimeter that will
begin observing from the South Pole in late 2010. The initial deployment will
consist of three telescopes similar to BICEP2 housed in ultra-compact, pulse
tube cooled cryostats. Two more receivers will be added the following year. In
these proceedings we report on the design and performance of the Keck cryostat.
We also report some initial results on the performance of antenna-coupled TES
detectors operating in the presence of a pulse tube. We find that the
performance of the detectors is not seriously impacted by the replacement of
BICEP2's liquid helium cryostat with a pulse tube cooled cryostat.
