CERN’s Large Hadron Collider is frosty and beaming, once again, after more than a year of repairs and testing that followed the eruptive escape of liquid helium into the tunnel that houses the massive supercollider. The device has now been chilled to 1.9°K (-271°C), making it colder than deep space (2.7°K); and low-energy ions have already been beamed part way around the 27 km ring in anticipation of some high-energy collisions in about a month.
UPDATE: November 18, 2009 — After being taken off-line last month by a mere breadcrumb dropped by a passing bird, the world’s most expensive machine prepares to power up again. BBC news link.
More background on how the device works (BBC)