A particular pursuit
UVic scientists play key role in massive particle detector project

by Margaret Milne

The gleaming metal cylinders surrounding Dr. Michel Lefebvre represent more than five years of creativity and painstaking work by UVic scientists and technicians. With these devices, and the larger project of which they are a part, Lefebvre and his particle physicist colleagues hope to discover such secrets of the universe as why things have mass.

Lefebvre and one of the signal feedthroughs. (Darren Stone photo)

The fact that things have mass is a part of our everyday existence. “But where does the mass of an electron come from?” asks Lefebvre. “It’s a very fundamental question.”

Physicists suspect that particles have mass because of something called the Higgs field. The whole universe is filled with this field, the theory goes, and particles interact with the field to gain their mass.

“The Higgs field has a smoking gun—the Higgs particle,” says Lefebvre. If the field really exists, some kind of particle must also exist. Finding this particle would prove the whole theory true. So far, no one has found it, but physicists are betting that the Large Hadron Collider (LHC) will change all that.

The LHC is a 27km-long ring, buried 100 metres underground at the CERN Laboratory in Geneva, Switzerland. It whirls beams of protons around its circle, accelerating them to close to the speed of light. When the beams collide, “pure energy freezes out into matter,” says Lefebvre. “New particles fly out, and we measure them.”

The LHC will be able to create higher energies, and heavier particles, than any experiment before it. It’s predicted that the Higgs particle could be found in the results of its collisions.
Building the LHC is a massive undertaking, involving scientists from more than 35 countries. One of Canada’s main contributions is work on ATLAS, a detector that will measure the particles created in the collisions. Canada is in charge of building calorimeters, devices that determine the energy of particles.

Since founding the ATLAS Canada collaboration in 1992, the Victoria group has grown to more than 20 scientists—students, research associates, technicians and professors. One of their current projects, funded by the Natural Sciences and Engineering Research Council, is building 55 signal feedthroughs. “These are devices that allow signals to go from inside the calorimeter to the outside world,” Lefebvre explains.

The calorimeters used at ATLAS operate at temperatures around –180°C. To design an electrical device that works with one end this cold and the other end at room temperature, UVic researchers spent many years constructing and testing prototype feedthroughs. They also collaborated with experts from other institutions, including TRIUMF—Canada’s national laboratory for particle and nuclear physics in Vancouver—and Brookhaven National Laboratories in New York. “Big science like ATLAS is very much a collaborative effort,” says Lefebvre.

Lefebvre has recently returned from a trip to Geneva where he saw a sample signal feedthrough being prepared for installation. “More feedthroughs will be shipped to CERN in the coming months,” he says, “and members of our team will go to CERN this fall to test them.”

The last of the signal feedthroughs should be completed by December, and the Victoria collaboration is planning a celebration to mark the milestone.

Margaret Milne wrote this as a participant in the SPARK program (Students Promoting Awareness of Research Knowledge), funded by UVic, the Natural Sciences and Engineering Research Council, and the Social Sciences and Humanities Research Council.