Last piece of ATLAS takes the plunge

On Friday 29 February the second small wheel was lowered 100 metres underground into the ATLAS cavern in front of a captivated audience. Although called the "small wheels" they are small in name only - each wheel is 9.3 metres in diameter and weighs 100 tonnes including the massive shielding elements. This piece completes ATLAS’ muon spectrometer, which has the ability to accurately track particles to the width of a human hair.

The first piece of ATLAS was installed in 2003 and, five years later, this small wheel is the final large piece of the detector to take the subterranean voyage to its final resting place.