Deep beneath the Canadian bedrock, scientists have cooled the SuperCDMS SNOLAB experiment to near absolute zero. This extreme environment marks a critical threshold in the hunt for elusive low-mass dark matter particles, officially transitioning the international collaboration from construction to detector calibration ahead of a full-scale search.
Reaching Ultracold Extremes Two Kilometers Underground
Deep underground in the Vale Creighton mine near Sudbury, Ontario, a massive cryogenic refrigerator has finally hit its target operating temperature. Located two kilometers below ground, the Super Cryogenic Dark Matter Search at SNOLAB has cooled to its operating temperature, dropping about 100 times colder than deep space and resting just thousandths of a degree above absolute zero.
That extreme chill is not just for show. It acts as a necessary shield against thermal noise, silencing vibrating atoms that might otherwise mask the faint signatures of dark matter. Dark matter makes up about 85% of all matter in the universe, yet it interacts so weakly with ordinary matter that it has long evaded direct detection.
Inside the subterranean laboratory, the experiment houses 24 ultrapure silicon and germanium crystals, each roughly the size of a hockey puck. When a dark matter particle collides with one of these crystals, it generates a tiny vibration known as a phonon alongside a small electrical signal. To register those minuscule signatures, the crystals rely on superconducting sensors that function exclusively under ultracold conditions.
“Reaching this ultracold temperature means our experiment has crossed a major threshold.”
Enectali Figueroa-Feliciano, Northwestern’s SuperCDMS lead
With the cryogenic milestone cleared, researchers can finally turn on the detectors and begin calibrating the equipment. Detecting dark matter would not only reveal the identity of most of the universe’s mass, but it could also unlock an entirely new realm of particle physics.
Simulating Particle Collisions Underground at NEXUS
Before the collaboration can identify a genuine dark matter collision, researchers must understand precisely how the detectors respond to known particle interactions. To solve that problem, a team led by Northwestern University and the Fermi National Accelerator Laboratory built a specialized facility called the Northwestern Experimental Underground Site, or NEXUS.
Situated 106 meters below Fermilab, NEXUS benefits from thick lead shielding and an underground footprint that blocks interfering cosmic rays. The facility utilizes a dedicated neutron beam and neutron detector to mimic what researchers expect to see inside the deep Canadian mine.
“This combination allows NEXUS to use the neutrons from the beam as a stand-in for dark matter events in the detector.”
Enectali Figueroa-Feliciano, Northwestern University
That setup provides researchers with a controlled way to calibrate the detectors and measure a quantity called ionization yield. Without those precise measurements, scientists would have no reliable way to distinguish a real dark matter signal from ordinary background radiation.
Early Science Data Collection and the Path to 2027
Even as the collaboration fine-tunes its baseline calibrations, the experiment has officially entered its early-science data-taking phase. SuperCDMS SNOLAB has begun collecting its very first scientific data, giving researchers an immediate opportunity to test system performance.
“The search for dark matter at SuperCDMS SNOLAB is finally underway.”
Tina Cartaro, SuperCDMS Operations Manager at the Department of Energy’s SLAC National Accelerator Laboratory
The current early-science phase will run through the fall of 2026. Following that initial data collection, the operations team plans to temporarily warm up the facility to optimize both the cryogenic systems and the surrounding noise environment. That maintenance period will extend into late 2026, leading directly into a full year of data collection with the detectors running at optimized, full sensitivity.
Supported by 28 institutions globally and led by the Department of Energy’s SLAC National Accelerator Laboratory, the project pairs improved hardware with modern analysis techniques. With many more sensors per detector than in the previous SuperCDMS Soudan experiment in Minnesota, alongside new simulation tools and artificial intelligence-enabled reconstruction, the resulting dataset will be far richer than initially planned.
Unprecedented Sensitivity for Light Dark Matter
The primary objective for the SNOLAB experiment is hunting down light dark matter, a category of hypothetical particles so lightweight that their interactions with ordinary matter leave only the faintest traces. The collaboration’s setup uses layers of copper, polyethylene, ultrapure lead, and radon barriers to shield the crystals from stray radiation.
“Our detectors will explore, with unprecedented sensitivity, regions where the lightest-mass dark matter particles may be lurking.”
Priscilla Cushman, SuperCDMS spokesperson and professor at the University of Minnesota School of Physics and Astronomy
Beyond the core dark matter search, the experiment’s heightened sensitivity will allow researchers to probe previously inaccessible energy scales. The SuperCDMS SNOLAB project itself is a joint effort backed by the U.S. Department of Energy Office of Science, the U.S. National Science Foundation, the Canada Foundation for Innovation, the Natural Sciences and Engineering Research Council of Canada, and the Arthur B. McDonald Institute in Canada. With the detectors now cold and data flowing, the collaboration is positioned to begin unlocking new physics.
