Page 23 - EUREKA! Fall 2017

preliminary dark matter search data in
anticipation of collecting up to 10 to 15
dark matter scattering events during
full four-year detector running period.
When the detector is triggered by
a radioactive event, data is recorded
from each of the PMTs at a rate of
about five megabytes of data per
second. That will add up to roughly
250 terabytes per year. All this
information is stored (and backed
Photo: Luther Caverly the Compute Canada network, and
up) at a data centre that’s part of
is analyzed by researchers from the

The DEAP team released the
Vollignis sam quis dolendia dolenihicia inctoratum explit remperum fuga. Nemquatius ea qui utatum project’s partner institutions.
experiment’s first results at a
Cross Pollination conference in Sudbury in late July, a
paper that demonstrated the best-ever
PhD student Andrew Erlandson finds a new home at SNOLAB rejection of radioactive backgrounds
using liquid argon, and the lowest
level ever achieved of background
radon, one of the most troublesome
When he’s not on campus in Ottawa, that had been built on the Carleton tubes emit flashes of light — they’re backgrounds in dark matter searches.
Carleton PhD student Andrew campus was moved to Chalk River, supposed to be detecting light, but if they “The early indications are positive,”
Erlandson splits his time between and somebody with expertise in high- shake or “get noisy,” they can emit light. Boulay says about the data analysis
a pair of unique workplaces. In the energy physics and detector hardware So the research team is systematically conducted to date. “We know
summer, he’s in Chalk River, Ontario, at development was needed. combing through the preliminary DEAP that dark matter exists and affects
Canadian Nuclear Laboratories (CNL), Erlandson’s specialty is “muon data to see if this is happening, and if our universe at many scales. The
the country’s leading nuclear science tomography,” an imaging technique that it’s causing a background disturbance hypothesis that many people have
and technology organization, a two- uses cosmic ray muons to generate 3D they need to be worried about. He’s also is that it’s a new particle that we’ll
hour drive up the Ottawa River from images of volumes. It was developed looking at effects of “process systems” on be able to detect directly. What
the capital, where he’s been working in the 1950s, and was famously used detector data: if a cryogenic cooler starts we don’t know is the mass of that
as a physicist since 2013. Throughout by American physicist Luis Alvarez in up or shuts down and thermodynamic particle, or how often it will interact
the academic year — thanks to a CNL the 1960s to look for hidden chambers changes happen — if the liquid argon with regular matter. When you mount
program that covers educational inside a pyramid in Giza. Muon detector starts to change in density — some an experiment like this, those two
expenses for exceptional employees — technology only caught up in 1980s of the characteristics of the detector parameters are unknowns, and if you Photo: Luther Caverly
he takes periodic trips to SNOLAB to and 1990s, built out of recycled particle could change. This has to be very well observe something you can pinpoint
assist his PhD supervisor Mark Boulay detectors from collider experiments. understood. which sets of those parameters — dark
on the DEAP-3600 project. “These things are very expensive to “It puts everything in perspective matter particle mass and its probability
“It’s very convenient,” Erlandson says build, and after experiments are finished because I’m used to seeing everything on of interacting — are consistent with the Mil mossus. Ro elliquis qui volessitaes doluptaquas expernatum si destrum sit
omnimuscia iusdae. Am nos aut ma voloribus et optatia denderro berit facimag niminci
about the geographic proximity that they typically sit and collect dust,” he computer screens,” Erlandson says about observation. If you don’t see anything, liquae nonsequ atemperspit exerruntenis quid quam qui abor minctor eperfero eseniaesti
makes it easy to travel between the says. “Might as well re-use them.” his time onsite at SNOLAB. “Seeing how you can rule out part of that parameter
three sites. “There’s so much world- Despite his focus on this work at large the detector and laboratory space space and push farther and farther
class research going on in this part of CNL, when Erlandson’s colleagues are definitely gives me a better grasp of down in sensitivity. go in particle physics.” Boulay. “Most experiments right now
Ontario. Canadian Nuclear Laboratories told him about the DEAP project, he the context for all the analysis.” “It’s extremely exciting be part of After getting his training and in particle astrophysics are probing the
and SNOLAB both attract people contacted Boulay and asked about As the experiment progresses, this experiment,” he continues. “It’s starting his research career on the unknown. In the case of SNO, we knew
from all over the world, and Carleton’s starting a PhD. “The potential for Erlandson explains in the SNOLAB exciting to have the world’s leading SNO experiment, DEAP is a natural we would either see that neutrinos
physics program also attracts people discovery is so high, it’s a world leader, lunchroom, his role will evolve. He’s not facility for underground science so evolution for Boulay. There’s pressure changed flavour or they didn’t —
from all over the world, so there’s a lot the first liquid argon detector of its sure exactly what he’ll be doing in the easily accessible to us. At any point in to maintain the high standards that and either one of those would have
of cross-pollination of ideas.” kind, that’s what really drew me,” years ahead, although the possibility the next six months or year, we may were set with SNO, he says. Although, been a momentous result. Now we’re
Before starting at CNL, Erlandson says Erlandson. “Thinking in a more of using liquid argon and dark matter for the first time see direct evidence in a sense, that foundational work searching for things with experiments
did a master’s degree at Carleton, practical sense, the technology that’s technology for nuclear security research of this material that essentially the would be considered low-hanging fruit such as DEAP and nEXO and there’s
working with professor John Armitage being developed for DEAP could down is intriguing. Erlandson never saw universe is made of. It would certainly today — “they knew what they were not really a firm prediction about what
on a prototype muon detector to the line be used for other applications.” himself working at SNOLAB, but, as is be a paradigm shift. Once you have looking for” — whereas DEAP is more we will see. So, we’re more in a search
detect illicit nuclear materials at ports In the early stages of the experiment, often the case when particles or people direct observation of a dark matter of a voyage into the unknown. “With mode, trying to discover the unknown.
of entry. “It was nuclear security and Erlandson has primarily been looking at collide, you can never be sure of the particle, you can start looking in more SNO, we knew one way or the other, as “The way I would phrase it, we’re
particle physics coming together,” some “instrumental affects” that were results. “I talked to the right person on detail at the data and rule out or rule long as the experiment could be made opening a new window on the universe
he says — a combination that led to observed during the original operation of the right day, and we talked about the in various theories of particle physics. to work technically, that the answer that we haven’t looked through
his opportunity at CNL. A detector the detector. Sometimes photomultiplier right thing, which sent me on this path.” It will provide a road map for where to would be extremely interesting,’ says before.”

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