12 days of SNOLAB science

This year SNOLAB has once again marked the holiday season by sharing 12 days of SNOLAB science on our social media platforms, where each day highlighted the cutting-edge research, infrastructure, and people responsible for the deep underground science taking place at our facility.

Day 1: One muon/cm2/min cosmic ray flux 🌎

SNOLAB is located 2km underground to avoid the cosmic rays that bombard the surface of the Earth and would overwhelm our sensitive experiments. On the surface of the Earth, 1 cosmic ray particle will pass through an area of 1 square centimetre every minute. This is roughly equivalent to 1 cosmic ray passing through your hand every second! The 2km of rock between surface and the SNOLAB underground laboratory is very effective at blocking these cosmic rays. In the underground lab, you would have to hold your hand out for several months before a cosmic ray would pass through your hand. Or, for those that want the stats – there is 0.27 muons per square metre per day in the underground lab.

Day 2: Two machine shops 🔩

SNOLAB’s world class science takes more than just a science team to run smoothly! Two supports that are essential to the research taking place deep underground are our machine shop facilities – one is located underground, and the other is located on surface. The Technical Services team maintains and operates these facilities to provide vital support to the experiments and laboratory as a whole. The machine shop spaces have lathes, milling machines, drill presses, water jet cutters, and more to keep things running smoothly!

Day 3: Three process tanks in the Tellurium Diol plant 🧪

The SNO+ experiment uses a unique cocktail of chemicals to study neutrinos. The liquid scintillator currently located in the acrylic vessel of SNO+ will have a mixture of other additives to improve the search for neutrinoless double beta decay. These additions include tellurium and butanediol which is used to keep the tellurium in solution with the liquid scintillator. This process requires specialized chemical plants in the underground laboratory to create these unique mixtures to the cleanliness standards required at SNOLAB. The Tellurium Diol plant contains 3 process tanks and there is a team of engineers, operators, and researchers working on this project. It is currently in commissioning and will be moving towards full-scale testing.

Day 4: Four acid etching baths 🛁

The SuperCDMS experiment has been preparing the copper vessels that will be located at the heart of the experiment for installation underground. Rare event searches require very low radioactive backgrounds in order to be able to detect signals. A way of reducing these signals in the copper is through a process called acid etching that removes 1 micron per minute of the outer layer of copper. Removing this thin outer layer removes radioactive backgrounds and improves heat transfer. Each of the baths represents a different step in the process: etch, rinse, passivate, and rinse again. It takes place in the surface cleanroom before being shipped underground to SNOLAB. This process involves coordination of the science division, projects group, and operations team.

Day 5: Five golden tiers on the SuperCDMS fridge ❄️

The SuperCDMS experiment, currently under construction at SNOLAB, will operate at extremely cold temperatures of about –273 degrees Celsius! To achieve such an extreme temperature requires more than your average fridge. SuperCDMS uses a dilution refrigerator with 5 stages that mix two isotopes of helium to achieve this incredible temperature. SuperCDMS will use this extremely cold temperature to cool their silicon and germanium crystals so that the atoms are barely moving. This will allow the experiment to see small vibrations, called phonons, created by particles interacting inside the experiment. You might say it’s pretty cool!

Day 6: Six surface clean room labs 🔎

In order to support and enable the underground science happening at SNOLAB, there is a full surface clean lab space. The surface laboratory space replicates the cleanliness of the underground laboratory to allow for work to be done in a similar environment – minus the 2km of rock overheard! This space is managed by the scientific support group and includes 6 individual labs, each with their own purpose ranging from a fully equipped chemistry lab, low background counting labs, and a staging area where clean items can be prepared to be shipped underground.

Day 7: 7000 tonnes of UPW recirculating around SNO+ 💧

SNO+ is one of the many experiments that use water as a shield for background signals around the experiment. The water used isn’t ordinary water though, it is ultrapure water (UPW) that has all the impurities and minerals removed. This leaves the hydrogen and oxygen that compose water and some nitrogen that has been added. This means the water is extremely clean and does not introduce unwanted signals in the experiments while also blocking out unwanted backgrounds. A water plant underground and a world-class team makes this possible. The plant includes a degassing process that removes gases, such as radon, and replaces them with nitrogen. The SNO+ experiment is the largest of the experiments using UPW at SNOLAB and has 7000 tonnes of water surrounding it.

Day 8: Eight particle counters in the underground clean lab 📉

To achieve the particle counts required by the experiments at SNOLAB, the lab is maintained as a class-2000 clean lab. This means that in a cubic foot of space, there are no more than 2000 particles that are a half micron in size or larger. To provide a sense of scale, this is 100 times smaller than a strand of human hair! Particle counters are located throughout the underground laboratory that monitor, in live time, the number of particles in various locations in the lab to ensure a class-2000 cleanliness level is maintained. An eye sees dust when sunlight passes through it, illuminating the individual particles, your eyes see the reflection of the light from the dust. The particle counters use this same principle with lasers and sensitive light detectors to illuminate particulates, seeing and counting the reflections from the individual particles.

Day 9: Nine shaft at Creighton Mine 🪨

At SNOLAB we access our unique underground laboratory through Vale’s Creighton Mine #9 shaft. This vertical access allows us to move personnel and equipment underground. The mining elevator, called the cage, has two levels and is able to transport about 90 people underground in one trip or two railcars of equipment in a single trip. This important partnership allows SNOLAB to focus on maintaining a facility for world-leading science.

Day 10: Ten tonne monorail crane in the Cube Hall 🏗️

The Cube Hall is a large, square shaped cavern at SNOLAB that measures roughly 15 meters high. There is a staging area in the top portion of this space and a deck about halfway up. Built into to the top of the cavern is a bright yellow, 10 tonne monorail crane that is used for hoisting materials to the various levels of this large underground cavern. With three large-scale dark matter experiments underway in the Cube Hall, the 10 tonne monorail crane has been getting good use moving critical materials for experiments over the years.

Day 11: Eleven compressed gas cylinders ☁️

SNOLAB uses a variety of inert gases to help experiments run smoothly. Primarily, nitrogen is used in the cover gas systems for several experiments. A cover gas protects the experiment from pressure changes that happen in a mining environment, prevents mine air from entering the experiments, or is used as a cover gas to ensure that the experiment’s operating pressure remains constant. Gases such as helium can be used to leak-check different experimental components, ensuring they are sealed to prevent the ingress of mine air and to maintain safe operating pressures.

Day 12: 12-gauge wire to power the lab 🎄

The underground laboratory space requires a large amount of electricity to keep everything running. Power from the surface begins as 13 800V, and as it travels through the drift and into the laboratory drops to 600V. This is then distributed throughout the lab. This power is distributed in part by 12 American Wire Gauge (AWG) wires, that work to deliver power to everything from the lights to the outlets. Wires twisted together as pictured can help reduce electrical noise, important in delivering clean and consistent power to experiments and their infrastructure. You might say the use of 12-gauge wire really keeps our spark for research alive and lights up our (underground) world.