Canadian scientists make history by trapping antimatter atom

York physics Professor Scott Menary is among an international group of scientists that has successfully trapped antihydrogen atoms for the first time, according to a paper published yesterday in the journal Nature.

The experiment, conducted at CERN – the European Organization for Nuclear Research – used magnetic fields to trap the antimatter atoms for a tenth of a second – long enough to study them.

Antimatter – or the lack of it – is one of the biggest mysteries of science. During the big bang, matter and antimatter should have been created in equal amounts. “The question is, why are we left only with matter? Where did all the antimatter go? Successfully trapping antihydrogen is a huge step forward,” says Menary, a professor in York’s Department of Physics & Astronomy in the Faculty of Science & Engineering. “It opens up a whole new avenue for comparing and understanding matter and antimatter.”

The most direct route to answering that question is to take one of the best-known systems in physics, the hydrogen atom – consisting of one proton and one electron – and check whether its antimatter counterpart, antihydrogen, behaves exactly the same way.

Left: Scott Menary

Menary works on the Antihydrogen Laser Physics Apparatus experiment, dubbed ALPHA, at CERN. The Nature paper was published by the physicists of the ALPHA collaboration, with a major Canadian component including scientists from the University of British Columbia, Simon Fraser University, the University of Calgary, and Canada’s national laboratory for particle and nuclear physics, TRIUMF. Of the paper’s 42 authors, 15 are Canadian.

Scientists at CERN were able to make antihydrogen almost a decade ago, but they couldn’t study it; antimatter annihilates when it comes into contact with matter, converting to energy and other particles. ALPHA scientists succeeded by constructing a sophisticated “magnetic bottle” using a state-of-the-art superconducting magnet to suspend the antiatoms away from the walls of the device and keep them isolated long enough to study them.

Still, some might ask, why put all this effort into studying something we can’t perceive?

“That’s how it is with scientific discovery. You don’t know what will come out of it, precisely. It’s a long-term investment,” Menary says.

Right: The gold electrodes for the ALPHA Penning trap are being inserted into the vacuum chamber and cryostat assembly. This is the trap used to combine or “mix” positrons and antiprotons to make antihydrogen. Photo by Niels Madsen ALPHA/Swansea.  

Makoto Fujiwara, research scientist and spokesperson for ALPHA-Canada, notes that the group is already pushing ahead with new experiments on the trapped antihydrogen. “As we speak, we are trying to measure, for the first time, what colour antimatter atoms shine,” he says, referring to attempts to apply microwave spectroscopy to antihydrogen. This effort is the next step in determining its atomic structure in detail, which could give new clues on why there is so much “something”, rather than a lot of “nothing”, in the universe.

Financial support for ALPHA-Canada came from the National Science & Engineering Research Council, TRIUMF, the Alberta Ingenuity Fund and FQRNT (Le Fonds québécois de la recherche sur la nature et les technologies).