LHC almost ready to be operational

Nov 13, 2007 15:04 GMT  ·  By

One of the last key components of the Large Hadron Collider-beauty has been finally installed. VELO or the Vertex Locator is built around the proton interaction region of the LHCb. LHCb is one of the four largest experiments at CERN's Large Hadron Collider, expected to be operational in 2008.

The Large Hadron Collider is in fact a particle accelerator, which - as its name says - studies the interactions between hadrons. Hadrons are composite particles, created from three quarks. Quarks are elementary particles that compose the protons and neutrons, and come in six flavors: 'up', 'down', 'strange', 'charm', 'bottom' and 'top'. For example, one proton is composed of two 'up' quarks and a 'down' quark.

The Large Hadron Collider-beauty experiment is one of the six particle physics detectors, constructed at LHC to study the parameters of CP violation in the interactions of b-hadrons, or heavy particles that contain a bottom quark. ('b', stands for beauty or bottom quark).

This is one of the most fragile detectors that were installed. It was constructed at the University of Liverpool, under the supervision of Professor Themis Bowcock, out of 42 modules that take over 1,000 hour to construct.

The Vertex Locator represents a particle-tracking detector which surrounds the proton-proton collision point inside the LHCb. At its core, the detector has 84 half-moon shaped silicon sensors, each connected to the electronics through a system of more than 5000 wires. They are located very close to the collision point, and will have the role of detecting bottom quarks, to understand the little differences between the matter and the antimatter behavior.

The sensors are packed in 42 separate modules, arranged in two halves, surrounding the beam line inside the Vertex Locator vacuum tank. An aluminum sheet provides shield between the silicon sensors and the primary beam vacuum. VELO also has extra flexibility, being able to retract from its normal position of just 5 mm from the beam line, to about 35 mm, a great advantage when you take in consideration the fact that the beam travels about 27 km through the ring of the LHC.

Responsible for the testing of the silicon modules was Dr Chris Parkes from the university of Glasgow LHCb team. Such testings are necessary, because the installation of the VELO is especially tricky and the modules could be damaged without even being aware of it. UK scientists have been greatly involved in the building of the VELO, and they are also responsible for the reception and testing of the modules, NIKHEF providing the special foil that interfaces with the LHC vacuum.