This is what they call the Cryopit -- it is the deepest, cleanest underground cavern of its size in the world. It will eventually house an experiment that requires super cold, cryogenic temperatures. 15 meters wide and almost 20 meters high!
It is my last day at SNOLAB -- what can I say -- it has been amazing!! The best thing about being here so many days in a row is getting the opportunity to understand so many things. As I look back on my notes from Monday, it all makes so much more sense. My tour guide, Blaire Flynn, and all of the employees have made me feel welcome and have willingly shared their knowledge and experience. I am so grateful for this opportunity! I would also like to take this opportunity to than the Canadian Association of Physicists for funding this trip of a lifetime!!
One discussion we had here today is the necessity of failure to the process of science. That is right -- I said failure! When you think about it, all of the experiments so far have not detected dark matter. Trial and error -- arguing and compromising -- throwing out and starting over -- all of this has been in the stories I have heard this week.
To be a true scientist, you must be comfortable with failing and starting over again. But that is easier to do when you truly understand the necessity of it!!
The DEAP experiment was our main focus today. It uses three and a half metric tons of cryo-cooled Argon inside it's acrylic vessel to try to detect Dark Matter. The temperature of the Argon is about -180 degrees celcius. Brrr.
It contains about 250 photo-multipliers (PMTs) that use the photoelectric effect to detect even the smallest amount of light. When an event occurs in the Argon it emits a tiny amount of light -- sometimes as little as one Photon. An event could consist of the Argon interacting with a muon, an alpha particle, a neutron -- and ultimately -- the pièce de résistance -- a (particle of) dark matter.
DEAP has been running since 2016 and will run about another three years. Students and Post-doctoral students are the individuals who usually analyze the data. However, there are many events happening all the time, but software (much of it designed and programmed by the physicists themselves) will weed out the 99% of known events. The data that needs to be studied is the events that are not yet known. The projection of Dark Matter events is about 1 per year. We know so far about Dark Matter is that is only interacts with gravity.
DEAP also rents time from the Center of Advanced Computing for their data analysis -- we are talking terabytes of data!!
People we spoke to that day:
Dr. Patrick Nadeau, DEAP Systems Operator, SNOLAB