B mesons live for about 1 millionth of a millionth of a second during which time they travel a few millimeters in LHCb before decaying. Precise tracking will allow the decay vertex point to be reconstructed from the daughter particles. The LHCb VELO (Vertex Locator) detector consists of 22 modules of silicon strip detectors each of which can resolve a particle that crosses it to 1/200th of a millimeter.

The University of Liverpool designed and built the silicon sensors and modules. See the video (left) or LHCb Liverpool Home for more information on this complex project that explains why and how the VELO is being built.

Modules are placed in the vacuum tank and taken down to 10-4 mbar. They are cooled with liquid CO2. All channels are read out and analysed to work out values for intrinsic detector noise, common mode, pipeline and pedestal effects. Results are logged to the electronic database. The experimental setup for testing modules at Liverpool.

A window in the vacuum tank allows the module to be photographed using a thermal camera. This lets you see hot-spots on the detector and pick up faults due to poor cooling or faulty electrical connections.

The first few modules sent to CERN were installed in a test-beam. Energetic protons were shot through the silicon modules and detected using the same readout electronics as will be used in LHCb itself.