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2,500 researchers, 1 supermachine, 1 new snapshot of the universe

April 01, 2008

Deep in the bowels of the earth -100 metres below ground in Geneva, Switzerland - lies a supermachine of 27 km circumference called the Large Hadron Collider (LHC) that has been built to unlock the mysteries of the universe.

Claude Leroy, a Université de Montréal physics professor, was among the 2,500 scientists from 37 countries recruited to help design, test and build the ATLAS detector at the supermachine that will provide a new perspective into what occurred at the time of the Big Bang and immediately after. Designed for CERN, the European Organization for Nuclear Research, the ATLAS detector, the largest among the four detectors operating at the supermachine in question, is 46 metres in length, 25 metres in height and 7000 tonnes in weight - or the size of three football fields.

Prof. Leroy was responsible for the radiation and irradiation studies conducted to ensure the ATLAS detector will run smoothly. His investigations also led to the creation of MPX, a small device attached throughout the supermachine and ATLAS that uses pixel silicon detectors to perform real-time measurements of the spectral characteristics and composition of radiation inside and around the ATLAS detector. The small devices essentially capture images of what's inside the detector and its environment, such neutrons and photons, a world-first.

He also participated in physics studies that targeted the production of heavy leptons, excited leptons, quarks and supersymmetry, in particular the study of neutralinos as dark matter candidates. Prof. Leroy's experiments were critical in ensuring the viability of the ATLAS detector at the core of the supermachine, which is the world's biggest particles physics detector. Indeed, before the LHC can be started up, some 38,000 tons of equipment of the supermachine must be cooled down to minus 456 degrees Fahrenheit for the magnets to operate in a superconducting state. This will be achieved by using liquid helium for magnet. Parts of the ATLAS calorimeters use liquid argon cooled at minus 312 degrees Fahrenheit. "The radiation field produced by the operation of the machine and ATLAS is stronger than a nuclear reactor, so it is vital that its design master all aspects of physics," said Prof. Leroy.

Supermachine's Big Bang

The LHC will recreate conditions akin to the Big Bang - which many scientists believe gave birth to the universe - by colliding two beams of particles at close to the speed of light. Since it is estimated that only 4 percent of the universe has been charted, the supermachine will help answer the following questions in physics when it is turned on in summer 2008:

* What is the unknown 96 percent of the universe made of"

* Why do particles have mass"

* Why does nature prefer matter over antimatter"

* What lies beyond Earth's dimension"



University of Montreal