Progress on CMS detector lowering

It was an amazing engineering challenge - the lowering of the first hugeendcap disc (YE+3) of the CMS detector slowly and carefully 100 metres underground. The spectacular descent took place on 30 November and was documented by a film crew from Reuters news group. The uniquely shaped slice is 16 m high, about 50 cm thick, and weighs 400 tonnes. It is one of 15 sections that make up the complete CMS detector. The solid steel structure of the disc forms part of the magnet return yoke and is equipped on both sides with muon chambers. A special gantry crane lowered the element, with just 20 cm of leeway between the edges of the detector and the walls of the shaft!

On 12 December, a further section of the detector (YE+2) containing the cathode strip chamber made the 10-hour journey underground. This piece is 16 m high and weighs 880 tonnes. There are now four sections of the detector in the experimental cavern, with a further 11 to follow.


The endcap disc YE+3 (seen in the foreground) begins its journey down the shaft from ground level. The next section to be lowered can be seen in the background.


There is just a small amount of leeway between the edge of the structure and the barriers in the cavern.


10 hours later, the disc touches the floor of the cavern.


The YE+2 section enters the shaft to begin its descent.


Arriving in the cavern. The previously section lowered can be seen in the foreground.


Checking the final measurements to ensure a smooth landing.