Interactions News Wire #69-05
24 August 2005 http://www.interactions.org
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Source: PPARC
Content: Press Release
Date Issued: 24 August 2005
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24th August 2005
87/05

Bon Voyage - heart of world's biggest physics experiment leaves the UK

After years of painstaking effort, the last of the 4 barrels that make up the central part of the Semiconductor Tracker (SCT), the heart of the biggest physics collaboration in the world has today (August 24th) left Oxford for its new home at the European Particle Physics Laboratory, CERN, near Geneva.

At CERN, physicists from around the world are assembling the Large Hadron Collider (LHC) which will send two counter-rotating beams of particles round an underground ring at 99.999999 per cent of the speed of light. When the beams are brought into collision, a shower of new particles will be produced reproducing conditions similar to those immediately after the Big Bang. These will be studied at four detectors around the ring. The largest of these detectors is called ATLAS and at its heart lies the SCT tracking the movements of the charged particles produced in the high-energy collision.

The SCT detector consists of a central region and two end caps. The central region is formed of four concentric barrels, covered with 2112 silicon modules (30 square metres worth!). The modules were produced by collaborators in different countries and sent to the University of Oxford for precision assembly. To be assembled, each of the fragile silicon modules had to be mounted on an ultra-lightweight carbon fibre cylinder using a specialised robot.

Each silicon module has 1536 channels, where each channel is a separate detector element which is connected by a wire bond to an individual channel of an ASIC (application specific integrated circuit) which contains all the read out electronics. Dr Richard Nickerson, who led assembly of the SCT at Oxford, said "the assembly of the SCT barrels has proved to be a very challenging project and so we are all extremely pleased to see it reach a successful conclusion with 99.5% of the 3 million channels working - even more than we hoped for as we had built in an element of redundancy."

Dr Tony Weidberg, also University of Oxford, said, "It has been both a privilege and a challenge to play our part in the world's largest physics collaboration. We now eagerly await the full assembly of the Atlas detector and the start of the LHC in two years time which will allow us to better study the nature of the Universe."

The SCT will track the positions of charged particles passing through the detector with an accuracy of better than 20 microns (less than the diameter of a human hair) over one metre. A superconducting solenoid will provide a magnetic field of 2 Tesla so from these measurements it will be possible to calculate the momentum of the particles, an important clue in sorting through the debris of a high energy particle collision. This information forms a crucial part of the data gathered by the full ATLAS Detector system and will be essential in the task of unravelling the physics in these complex events.

Other sections of the Atlas detector will pick up other particle properties. Between them, the different sections should allow a complete picture to be formed.

"The LHC will be the world's primary experiment to probe the structure of matter and forces of nature when it becomes operational in 2007," said Professor Keith Mason, CEO of the Particle Physics and Astronomy Research Council (PPARC) which funds UK involvement in CERN. Professor Mason added "UK research groups are involved in each of the LHC's four detectors and the SCT is a clear example of our technical expertise."

The ATLAS experiment is the world's largest collaboration in physical sciences, involving more than 1800 scientists from around the world. The detector is a leviathan, measuring 44m long and 22m high, as large as a five-story building, and weighing 7000 tons. Yet at its heart, where the SCT will operate, narrow beams of particles will be focussed to collide in an area much less than 1 square mm. Out of nearly 1000 million collisions a second, only a few will have the special characteristics that might lead to new discoveries.

Notes for Editors
The SCT is a collaborative international project with UK physicists coming from university research groups at: Birmingham, Cambridge, Glasgow, Lancaster, Liverpool, Manchester, Oxford, Queen Mary University of London, Rutherford Appleton Laboratory, Sheffield and University College London

Images
Images are available to download from http://www.pparc.ac.uk/Nw/BonVoyageSCT.asp

Contacts

Julia Maddock
PPARC Press Office
Tel 01793 442094
Email Julia.maddock@pparc.ac.uk

Dr. Tony Weidberg
University of Oxford
Tel: 01865 273370
Email: t.weidberg1@physics.ox.ac.uk

Grace Haydon
University of Oxford Press Office
Tel: 01865 280534

The Particle Physics and Astronomy Research Council (PPARC) is the UKs strategic science investment agency. It funds research, education and public understanding in four areas of science - particle physics, astronomy, cosmology and space science.

PPARC is government funded and provides research grants and studentships to scientists in British universities, gives researchers access to world-class facilities and funds the UK membership of international bodies such as the European Laboratory for Particle Physics (CERN), and the European Space Agency. It also contributes money for the UK telescopes overseas on La Palma, Hawaii, Australia and in Chile, the UK Astronomy Technology Centre at the Royal Observatory, Edinburgh and the MERLIN/VLBI National Facility, which includes the Lovell Telescope at Jodrell Bank observatory.

PPARC's Public Understanding of Science and Technology Awards Scheme funds both small local projects and national initiatives aimed at improving public understanding of its areas of science.