World-famous astrophysics lab located two kilometres underground in Vale’s Creighton Mine probes the secrets of the universe
SNOLAB takes its motto “Mining for Knowledge” literally.
We had just taken the cage down two kilometres into the bowels of the Earth at Vale’s Creighton Mine in Sudbury, famous scientists and hard-rock miners crammed together in the darkness like sardines. We walked through tunnels in miners’ outfits, scrubbed and dressed in clean suits and entered a class 2000 Clean Room of impressive dimensions glowing in the darkness of an active mine and following its strict production schedules.
SNOLAB is the world’s largest and deepest underground laboratory where extraordinary astro and particle physics projects have drawn the attention of scholars the world over, including two visits by Stephen Hawking who asked that the cage, speedy enough, go at full tilt.
Neutrinos
It was in the 1930s that astronomer Fritz Zwicki proclaimed that the universe consists of a substance we know nothing about. “Dark Matter” thus became as much an article of cosmological faith as of well-established theory. Now, that faith may have been rewarded. Just as researchers working at Europe’s Large Hadron Collider last year announced that they had bagged the Higgs boson, exciting news came from various sites about a particle of unbelievably small dimensions, detected in its oscillations by colliders shooting “neutrinos” to a detector shielded to measure at subatomic levels. SNOLAB has the distinct advantage over other sites of having the rock shield provided by the deep mine and free neutrinos from the sun that can be studied by some of the most advanced equipment of the New Physics.
Who builds such a thing? “A madman obsessed for years,” said SNOLAB director Dr. Nigel Smith.
Before us is the fabled “bubble,” the COUPP 60, its chamber filled with the fire-extinguishing liquid iodotrifluoromethane, a 60-kilogram detector awaiting those tiny bubbles that may unlock the mysteries of how the universe came to be and what constitutes matter called “dark,” “spooky” and “strange” by the very scientists who are most intimate with its nature.
Dark matter
Physicists theorize that dark matter interacts with ordinary matter by different mechanisms than other fundamental particles. WIMPS, weakly interacting massive particles, the leading candidates for dark matter, may be dependent or independent of the nuclear spin of the atoms in the detector material. The DEAP 1 and DEAP 3600 detectors in a Canadian-led research project use liquid argon to study the “spin-independent properties” of WIMPS. The “spin-dependent properties” of WIMPS belong to the PICASSO project. WIMPS interact in the detector by “nuclear recoil,” which the miniCLEAN project hopes to exploit using liquid argon to “scintillate,” or light up the event.
The Helium and Lead Observatory (HALO) project looks from underground far into space for a Supernova, the large burst of neutrinos that occurs when a star explodes. Supernovae happen two to four times a century. Deep underground, 79 tonnes of annular lead blocks instrumented with 128 tubular Helium-3 await the “event “ no accelerator could duplicate on Earth. Dr. Smith’s eyes light up at the thought that his SNOLAB would set off the worldwide Supernova Early Warning System (SNEWS) and allow professional and amateur instruments to observe an event which astonished Queen Elizabeth 1 in 1572.
But it is the mysterious solar neutrinos which most intrigued scientists over the last decades and has been the special province of SNOLAB. Neutrinos have no charge and interact with other particles only through weak nuclear force and gravity. They zip through us to the centre of the Earth or the Milky Way by the billions just a little short of the speed of light. For decades listed as “missing” during their journey from the sun to Earth, solar neutrinos are in fact changing form in a cosmic dance in which they are seemingly in two places at once and nowhere at all. They leave the sun in electron neutrino “flavour” or type, “oscillate” along the way and arrive undetected as a muon neutrino with an altogether different character or “flavour.” That was suggested in the original Sudbury Neutrino Observatory (SNO) experiment and in more recent tests conducted at SNOLAB, the expanded facility accommodating multiple experiments.
Smith hopes that the predicted “neutrinoless double beta decay” may similarly be established by the SNO+ experiment to explain how the original balance or “symmetry” between positively and negatively charged particles broke down, creating the universe as we know it. That would be big bang indeed in the world of particle and astrophysical sciences.
Kaboom
We are sitting in the cafeteria. Smith’s meal, slivers of vegetables, each in its separate compartment, is interrupted by a dull “kaboom.” An assistant rushes out to check. “They are blasting,” says Smith, leaving to check his instruments. In fact, fully 20 per cent of the operating cost of SNOLAB is accounted for by the Vale Creighton operation and, indirectly, on over a century of mining technology.
“What really makes us unique is our scientific program building unique pieces of infrastructure,” Smith explains. SNOLAB is the host providing and servicing a very large facility with some 70 employees, including engineering designers and maintenance crew, serving 250-300 top scientists from around the world who pass through Sudbury.
SNOLAB provides space for carefully screened projects that need support over a lifecycle of prototyping and operation, and bring project money and the complex and beautiful instruments of the New Physics to Sudbury. Invisible as a neutrino today, they may in time awaken by news of discoveries a thirst for science.
There are practical applications in the mining industry for the data management resources of particle physics. “As an international network of scientists, we need to bring together disparate data sets from very widely scattered particle and astrophysicist communities around the world,” said Smith. “This in the true sense of the word is data mining which could be of use to the mining industry in organizing and exploiting the many sources of information in mining operations.”
Astrophysics research
Smith paid special tribute to Canadian governments at the federal and provincial levels for funding SNOLAB when so many other governments have withdrawn funds for astrophysics research. Secure for five years, SNOLAB is funded by the International Joint Venture Program of the Canada Foundation for Innovation, the Ontario Innovation Trust, the Northern Ontario Heritage Fund Corporation and FedNor, and run co-operatively by Laurentian University, Carleton University, Queen’s University, the University of British Columbia, the University of Guelph and the Université de Montreal.
Clearly, Canada has leveraged its $7.5 to $8-million program to take the country to the centre stage of what is already advertised as the “Century of the Neutrino.” It is money well spent. SNOLAB is one cool laboratory.
