SuperCDMS Goes to Extremes to Find Dark Matter
Professor Priscilla Cushman of the School of Physics and Astronomy and her group are part of the hunt for one of nature’s most elusive substances – dark matter, which makes up 85% of all matter in the universe. This endeavor has scientists going to extremes.
Deep underground and chilled to near absolute zero, the Super Cryogenic Dark Matter Search (SuperCDMS) SNOLAB – one of the world’s most sensitive dark matter searches – has begun collecting its very first scientific data, following a six month commissioning period for the newly installed experiment. This initial science run is planned to last just a couple of months, taking the experiment through the annual summer planned maintenance period for the Vale mine that hosts SNOLAB.
The data collected over these months is the first science data from the experiment and may produce world-leading results in selected detectors, as well as valuable diagnostics of the experiment’s full detector payload and its surrounding cryogenic cooling system. The SuperCDMS Collaboration and Operations team plans to follow up the first data-taking run with a warm-up of the experiment to replace a faulty cryogenic element and to further optimize the cryogenic system and the noise environment. This warm-up and repair period is expected to extend into late 2026, and will be followed by a year of science data collection with optimized detector operation.
Above: The low background shield being completed, showing layers of increasingly radiopure lead moving inward to the sensitive detectors embedded in an inner polyethylene castle and a mu metal shield to eliminate the effect of Earth’s magnetic field. The mosaic of thin bricks over the top is made from ultra-pure lead sourced from ancient sunken ballast in the Mediterranean. The rest of the lead roof needs to be installed using the vacuum lifter (device with the suction cups), one slab of which is shown in the picture. Below: The experiment ready to take data with the aluminum radon barrier installed around the lead and poly shielding, but prior to the installation of the outer water tanks. The Cryocoolers, vacuum interface and warm electronics, and deployable calibration system are visible in the foreground with the dilution fridge behind the shield.
"The search for dark matter is finally underway," said Tina Cartaro, SuperCDMS Operations Manager at the Department of Energy's SLAC National Accelerator Laboratory. "Even in this early phase, our most sensitive detectors have the potential to deliver breakthrough discoveries. At the same time, we're preparing and testing the entire system, learning how our detectors and cryogenic cooling perform together so we can unlock their design sensitivity.”
SuperCDMS is an international collaboration of 28 institutions. This second-generation experiment is designed to detect “light” dark matter, hypothetical particles so lightweight that their interactions with ordinary matter leave only the faintest traces, making them especially hard to detect. SuperCDMS houses 24 ultra-pure silicon and germanium crystals, each about the size of a hockey puck, inside a refrigerator colder than outer space. If a dark matter particle strikes one of these crystals, it will produce a tiny vibration called a phonon, along with a small electrical signal. To detect those minuscule signals, the crystals are outfitted with superconducting sensors that only work when they are extremely cold. The entire set-up is surrounded by layers of clean shielding materials to prevent stray background radiation from drowning out the signal. Layers of copper, polyethylene, ultra-pure lead (pictures 1 and 2) and a barrier against radon (picture 3) are used to reduce these backgrounds to acceptable levels.
The early-science phase will continue through Fall 2026. Following this early data-taking period, the SuperCDMS Collaboration and Operations team plans to warm up the experiment to further optimize both the cryogenic system and noise environment. This warm-up and maintenance period is expected to last into late 2026, followed by a year of data collection with the detectors running at optimized, full sensitivity.
“Our detectors will explore, with unprecedented sensitivity, regions where the lightest mass dark matter particles may be lurking,” said SuperCDMS spokesperson Priscilla Cushman, a professor in the University of Minnesota School of Physics and Astronomy. “We are only sensitive to them once we have eliminated the interference of the much more abundant background particles by going deep, going cold, and encasing the detectors in layers of radiopure shielding.”
The SuperCDMS SNOLAB experiment is a joint project of 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 (Canada).