U of A physicist helping build next-generation particle detector to shed new light on dark matter

Aksel Hallin and his team will put their pioneering expertise to work on a newly funded Canadian collaboration aimed at revealing clues to one of the universe’s greatest mysteries.

Michael Brown - 03 March 2021

In the 1930s, Swiss astronomer Fritz Zwicky noticed that a cluster of galaxies moved as if the system contained more matter than what was expected by observing light that is emitted by normal matter.

“If you look at a galaxy, the stars at the edge of the galaxy in the spiral arm are travelling almost as fast as the stars in the middle,” explained University of Alberta astroparticle physicist Aksel Hallin, a professor in the Faculty of Science. “This would be impossible without something else there to provide the gravity to hold it all together.”

This phenomenon seen in the stars, how light bends around galaxies and a whole set of measurements all point to there being a lot of extra mass in the universe that is not normal chemical mass. In fact, it is estimated that normal matter accounts for just five per cent of the universe.

“That's a big chunk that is missing,” said Hallin. “We know it has to be there, a particle that we don't understand.”

He added, “This mystery surrounding dark matter is on the top 10 list of holes in our scientific understanding.”

To help fill this hole, the federal government, through the Canada Foundation for Innovation (CFI), is investing $6.35 million in a $15.9-million Canadian research project, of which $2.75 million is coming to the U of A, with the rest being split between Carleton and Queen’s universities.

Hallin, who is a co-lead on the grant, said his team has been called upon to do what it does best—build the liquid-argon dark matter detector, otherwise known as a time projection chamber.

“The building of these large acrylic structures, which allows us to measure very precisely the energy and position of radioactivity in a big volume, is really something that we've pioneered,” said Hallin.

Similar structures were used in the creation of the Sudbury Neutrino Observatory (SNOLAB)—in which the U of A is a partner—which, at two kilometres below the Earth’s surface, is shielded from cosmic rays so it can provide a low-background environment to look for, among other things, dark matter.

Researchers at SNOLAB proved that neutrinos—subatomic particles created in the core of the sun—have mass and change type, a discovery for which Queen’s physicist Arthur McDonald won the 2015 Nobel Prize in physics.

The new CFI funding will include upgrades to the current DEAP-3600 experiment, along with contributions to the Darkside-20k experiment starting in Italy in 2023, that will allow development of the ultimate argon detector at SNOLAB in the not-so-distant future.

“If we are going to be in the group of countries that do this kind of research—the U.S., the U.K., Germany—this research is at the heart of their university systems,” said Hallin. "It also creates a connection between industry and fundamental science.”

He noted if students can compete in these settings, at the leading edge of basic science and technology, they can compete anywhere.

“It’s a way for our students to be working shoulder to shoulder with students from the premier universities in the world.”

And the promise of this research is almost limitless. Hallin said if we were to go back 100 years, academics were beginning to tinker with quantum mechanics and detractors said it was useless.

“Nobody said, we're studying quantum mechanics because it's going to lead to lasers and fibre optic communications, computer chips, transistors, integrated circuits and the information revolution—that sort of grew out of it when people realized how matter worked,” he said.

“That’s where we are.”

All told, five U of A-led projects received $24.1 million in CFI funding, of which $19.3 million is coming to the U of A. The balance will go to project partner institutions across Canada. An additional eight projects led out of partner institutions secured $8.2 million in CFI funding for the U of A. Proposals for matching provincial funding for these projects are with the provinces pending results.

CFI funding for physics projects led by U of A

Frank Hegmann, Jacob Burgess (University of Manitoba)
Ultrafast Nanoscale Quantum Dynamics (UltraNanoQD) Innovation
$3.9 million from CFI with $3.7 million coming to the U of A and $234,000 to U of M for project worth $9.7 million

Ian Mann
RADiation Impacts on Climate and Atmospheric Loss Satellite (RADICALS) Mission
$8.1 million in CFI funding, with $6.1 million coming to the U of A and $2 million to the University of Calgary for project worth $20.3 million

David Westaway, Michael Woodside
Protein Misfolding Scientific Exploration (ProMiSE) Team: Infrastructure Support for Remediation of Protein Misfolding
$3.9 million in CFI funding for project worth $9.6 million

CFI funding for physics projects where U of A is partner institution

Michel Fich (Waterloo), U of A principal investigator: Erik Roslolowsky
CCAT-prime: A Submillimetre Wavelength Survey Telescope in Chile
$4.9 million in CFI funding of which $750,000 is coming to the U of A. The total cost of the project is $28.8 million.

Mark Boulay (Carleton), U of A principal investigator: Aksel Hallin
Development of Next Generation Liquid Argon Dark Matter Detector and of an Underground Argon Storage Facility at SNOLAB
$6.9 million in CFI funding of which $3 million is coming to the U of A. The total cost of the project is $22.6 million.

Paul Barclay (University of Calgary), U of A principal investigator: John Davis
A Quantum Diamond and Hybrid Photonics (QDHyP) Foundry
$5.2 million in CFI funding of which $2 million is coming to the U of A. The total cost of the project is $13.1 million. 

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