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Past Winner
2004 E.W.R. Steacie Memorial Fellowship

Eric Hessels

Physics

York University


First, use a particle accelerator to produce hundreds of thousands of antiprotons careening at near the speed of light. Add equal numbers of antielectrons from the radioactive decay of sodium-22. Slow all down to a relative standstill by cooling them to four degrees Kelvin (or -269oC) – just a smidgen above absolute zero. Apply electric and magnetic fields to hold these antimatter building blocks in place in a particle trap.

Note: Make sure the world's purest vacuum environment is perfectly maintained or else the antimatter will combine with its matter counterparts, annihilating both in a burst of pure energy. If everything goes perfectly, you're on your way to cooking up antihydrogen – and helping solve one of the key questions in physics: are antimatter and matter perfectly symmetrical?

"Antihydrogen is amazingly difficult to create," says Dr. Eric Hessels, a professor of physics at York University and member of ATRAP, an international team that produced abundant antihydrogen atoms in 2002 at CERN, the European laboratory for particle physics, near Geneva. Dr. Hessels is one of six recipients of a 2004 NSERC E.W.R. Steacie Memorial Fellowship.

Helping produce antihydrogen was just the kind of high-end particle physics challenge that Dr. Hessels loves. His York University lab is a labyrinth of sophisticated physics gadgetry designed to make exquisitely precise atomic measurements.

Along with hunting antihydrogen, his other main project is a six-year-long epic journey to measure, to nine digits of accuracy, the energy required for an electron to jump orbits in a helium atom. He already holds the world record for this feat, equivalent to measuring the distance across Lake Ontario to less than the width of a hair. The measurement is important in that it enables physicists to more accurately calculate the fine-structure constant, a value that is a fundamental component of quantum physics calculations.

The precise measurement techniques Dr. Hessels has honed in his lab require the same patience and intense attention to details required to coax antihydrogen into existence.

Antihydrogen is the simplest antiatom, made of just a single antiproton surrounded by a positron (antielectrons are usually referred to as positrons). It's not known to exist naturally anywhere in the Universe.

Scientists first produced antihydrogen in 1996 at Fermilab near Chicago. But these antiatoms were moving at near the speed of light, too fast to be stored or studied. The challenge for the ATRAP team, and a group called ATHENA working concurrently at CERN, was to find a way to reliably create abundant antihydrogen that could be studied.

Enter Dr. Hessels, the antiparticle matchmaker.

"It's a little like having a handful of planets and a handful of suns. You can't just shuffle them together and hope that this amazingly delicate thing happens – that the planets start orbiting the suns. You have to somehow get them to start orbiting," says Dr. Hessels, who holds the Canada Research Chair in Atomic Physics.

With ATRAP, he helped develop a technique called three-body recombination, in which a positron is used as a cue ball to knock another positron into orbit around an antiproton to produce antihydrogen. The process occurs in a few-litre-sized metal tank (the one that's the world's purest vacuum environment) surrounded by a two-metre magnet.

The ATRAP team finessed making antihydrogen and producing millionth-of-a-second glimpses before an antiatom drifted away. (Since they're neutrally charged, the antihydrogen atoms can't be contained by using electric fields.) These fleeting glimpses were enough to begin the measurement of these antiatoms, including initial indications of how large they are.

As part of his NSERC Steacie research, Dr. Hessels will be working with the ATRAP team to contain antihydrogen in mid-vacuum using a magnetic field and will thus be able to watch, and measure it, for hours.

"We would like to do precise measurements of antihydrogen. We'd like to study the energy levels of antihydrogen with as high an accuracy as we can and then compare these energy levels with regular hydrogen," says Dr. Hessels.

These antiatom measurements are thought to hold decisive answers to fundamental questions about the structure of the Universe.

"This is going to tell us whether antimatter is a mirror image of matter and thus how symmetric the Universe is," Dr. Hessels says. While most physicists believe that matter and antimatter are identically symmetrical, the measurements of antimatter particles to date aren't yet accurate enough to seal the debate.

The ATRAP team consists of more than a dozen researchers from Harvard University, York University, as well as Jülich University and the Max Planck Institute, both in Germany.

As for building other antimatter atoms, Dr. Hessels says antihydrogen is hard enough and he's not even thinking about it.

"This more aesthetic sense of trying to construct an antiworld, objects made of antimatter, is a pipe dream," says Dr. Hessels. "It's Star Trek stuff."