Fermilab is providing technology and expertise for the SuperCDMS SNOLAB project, which will expand the hunt for dark matter to particles with properties not visible to any other experiment.
Fermilab’s Mark Ruschman tests prototypes for the SuperCDMS SNOLAB cryogenics system. Photo: Fermilab, Reidar Hahn
The U.S. Department of Energy Office of Science and the National Science Foundation have approved funding and start of construction for the SuperCDMS SNOLAB experiment, which will begin in the early 2020s to hunt for light dark matter particles. DOE’s Fermi National Accelerator Laboratory is playing a major role in building this new experiment, which is hosted at SNOLAB in Canada and managed by DOE’s SLAC National Accelerator Laboratory.
SuperCDMS SNOLAB will be at least 50 times more sensitive to low-mass dark matter particles than its predecessor, CDMS, at the Soudan Underground Laboratory, a Fermilab-led experiment that ended operation in 2015. SLAC is managing the SuperCDMS SNOLAB construction project for the international SuperCDMS collaboration of 111 members from 24 institutions in five countries.
“We are eager to resume our search for dark matter particles and explore an entirely new region of their possible interactions with normal matter,” said Fermilab scientist Dan Bauer, spokesperson of the SuperCDMS collaboration.
“Fermilab has been a leader in the search for dark matter for decades,” said Fermilab Director Nigel Lockyer. “We are proud to continue that involvement with the next generation of experiments, working with our U.S. and international colleagues at SNOLAB.”
A SuperCDMS SNOLAB detector and part of the readout wiring for the detector system. Photo: SLAC
A deeper, cleaner, colder search for dark matter
Scientists have long known that ordinary matter accounts for only 15 percent of all matter in the universe. The rest is a mysterious substance called dark matter. Due to its gravitational pull on regular matter, dark matter is a key driver in the formation of galaxies like our Milky Way. It therefore is fundamental to our very existence.
However, nobody knows what particles make up dark matter. Astronomical observations suggest that dark matter particles barely interact with the normal matter in the universe. Every so often, though, they could collide with an atom of our visible world, and dark matter researchers are looking for these rare interactions. These are difficult to spot in the presence of background interactions of normal matter particles from cosmic rays or small amounts of radioactivity in the environment.
In the SuperCDMS SNOLAB experiment, the search will be conducted using silicon and germanium crystals, in which the collisions would trigger tiny vibrations. However, to measure the atomic jiggles, these detectors need to be cooled to less than minus 459.6 degrees Fahrenheit — a fraction of a degree above absolute zero temperature. These ultracold conditions give the experiment its name: Cryogenic Dark Matter Search, or CDMS. The prefix “Super” indicates an increased sensitivity compared to previous versions of the experiment.
The experiment will be assembled and operated at the Canadian laboratory SNOLAB — 6,800 feet underground inside the Vale Creighton nickel mine near the city of Sudbury. There it will be protected from high-energy particles, called cosmic radiation, which can create unwanted background signals.
“SNOLAB is really looking forward to supporting the science delivery of the SuperCDMS SNOLAB experiment at our deep underground facility within the Vale Creighton mine, helping SuperCDMS SNOLAB fulfill its full potential as a leading dark matter search experiment,” said Nigel Smith, executive director of SNOLAB. “We were delighted to hear of the successful award of the DOE/NSF funding to SuperCDMS SNOLAB, and, with existing infrastructure support from the Canada Foundation for Innovation, look forward to the start of construction of SuperCDMS SNOLAB and deployment in Sudbury.”
Fermilab is responsible for the design and fabrication of the cryogenics system to produce the very cold temperatures required to operate the detectors. The design is based on that used for previous generations of the experiment but incorporates novel features that eliminate the need for large quantities of expensive liquid helium. The large copper vessels that will house the detectors must be as pure as possible to avoid radioactive backgrounds, and these must be shielded from environmental backgrounds by layers of lead, plastic and water. The cryogenics system must also be designed for remote operations, since the underground laboratory is not always accessible.
Fermilab scientist Lauren Hsu demonstrates the SuperCDMS SNOLAB calibration system prototype. Photo: Fermilab, Dan Bauer
“It is quite a challenge to design such a large cryogenics system to reach such cold temperatures using only materials that are nearly free of radioactivity and without constant access to the system,” said Fermilab physicist Matt Hollister, main designer of the cryogenic system for SuperCDMS SNOLAB.
Fermilab is also designing and fabricating electronics to control and read signals from the detectors. These electronics must have extremely low levels of noise in order to distinguish the small detector signals created by low-mass dark matter particles. The system for the new experiment is very compact, replacing a much larger chain of electronics modules from previous generations of CDMS.
“Reaching the low levels of electronic noise required for SuperCDMS is an ongoing challenge,” said Fermilab engineer Sten Hansen. “The levels we have achieved are due to the hard work of many throughout the collaboration.”
The response of the detectors to known particles must be understood to calibrate their expected response to dark matter particles. Fermilab is designing a system to allow the detectors periodic exposure to particle sources for such calibration.
“Previous generations of CDMS had to be calibrated manually,” explained Fermilab scientist Lauren Hsu. “The new experiment is designed so that calibration can be done more frequently and easily.”
A strong collaboration for extraordinary science
In addition to leading overall construction, SLAC National Accelerator Laboratory is building and testing the germanium and silicon detectors, and Pacific Northwest National Laboratory is helping to minimize and understand backgrounds for the experiment, a major challenge for the detection of faint signals from weakly interacting massive particles, also known as WIMPs, a candidate for dark matter.
Institutions in the United States, Canada, UK, France and India also play key roles in the experiment, working on all aspects of the experimental hardware as well as data analysis and simulation. The largest international contribution comes from Canada and includes the research infrastructure at SNOLAB.
“We’re pleased to be working closely with SNOLAB to manage the installation of this experiment,” said Fermilab scientist Pat Lukens, deputy project manager for SuperCDMS. “We’re eager to see the results of this next phase in the hunt for dark matter particles.”
Learn more about SuperCDMS at SLAC National Accelerator Laboratory’s website.
Fermilab’s Dan Bauer, spokesperson of the SuperCDMS SNOLAB experiment, and Mark Ruschman in the Lab G cryogenics testing cleanroom at Fermilab. Photo: Fermilab, Reidar Hahn
Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance LLC, a joint partnership between the University of Chicago and the Universities Research Association Inc. Visit Fermilab’s website at www.fnal.gov and follow us on Twitter at @Fermilab.
DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.
On Wednesday, April 18, Fermilab hosted its 11th STEM Career Expo in the Wilson Hall atrium. Approximately 1,100 Chicago-area high school students, parents and educators attended the event, where they had the opportunity to meet more than 160 STEM professionals from nearly 50 companies, organizations, agencies and professional associations.
The STEM Career Expo is an opportunity for students to take in the breadth of careers available in STEM. More than 60 types of professions were represented at the expo, including actuary, biomimicry architect, data scientist, distribution engineer, flavor chemist, forest ranger, health information manager, industrial hygienist, lubrication engineer, metrologist, patent agent, plant pathologist and water scientist — to name only a few.
The expo featured booths and tables staffed by STEM professionals as well as five panel discussions.
“This was our best attended STEM expo by both professionals and the public,” said Fermilab Office of Education and Public Outreach’s Susan Dahl, who organized the expo along with volunteer educators from Kane County and DuPage County schools. “Some people drove as much as 2-3 hours to be here.”
The event was funded by Fermilab Friends for Science Education and contributions from committee member schools.
Her Excellency the Right Honorable Julie Payette, Governor General of Canada, visited the U.S. Department of Energy’s Fermi National Accelerator Laboratory today, touring the lab’s extensive research complex and celebrating the start of a new partnership between Fermilab and York University in Toronto. The two institutions announced today the joint appointment of physicist Deborah Harris, who will lead York’s participation in the Fermilab-hosted Deep Underground Neutrino Experiment.
Her Excellency trained as an engineer and spent more than 20 years as an astronaut, flying two missions in space and serving as capsule communicator at NASA’s Mission Control Center in Houston as well as chief astronaut for the Canadian Space Agency. During her visit to Fermilab, she acknowledged the importance of collaboration and close science research partnerships between Canada and the United States.
Fermilab Director Nigel Lockyer, a graduate of York University and former director of TRIUMF, Canada’s national laboratory for particle and nuclear physics, highlighted the importance of research into these tiny particles.
“DUNE could unlock the mystery of why matter and the universe exist,” Lockyer said. “I’m delighted to be joining forces with the faculty and students from my alma mater to build the world’s most ambitious neutrino experiment.”
The Deep Underground Neutrino Experiment, together with the Long-Baseline Neutrino Facility, will send the world’s most intense beam of high-energy neutrinos 800 miles through the earth from Fermilab to the world’s most advanced neutrino detector one mile underground at the Sanford Underground Research Facility in South Dakota. LBNF/DUNE, which broke ground last July, will include contributions from scientists and engineers around the globe.
“The partnership with Fermilab is a reflection of York’s commitment to world-leading research,” said Ray Jayawardhana, dean of science at York University and author of the popular science book Neutrino Hunters, who joined Payette’s tour. “We are delighted to team up with the international collaboration building LBNF and DUNE, giving our researchers and students frontline opportunities to make significant discoveries on a global scale.”
York University President and Vice Chancellor Rhonda Lenton also noted the benefits this partnership will bring for the institution’s students and faculty.
“This exciting new partnership between York and Fermilab will highlight the research expertise available at York while providing real-world opportunities, not only for our researchers, but for our students,” Lenton said. “York will be on the forefront of research that could lead to discovering the role these tiny, yet abundant particles, neutrinos, play in the universe.”
The Governor General’s tour also highlighted many other areas of collaboration between Fermilab and Canadian universities and laboratories on particle physics and particle accelerator research. Canadian scientists were key contributors to the CDF and DZero experiments, which ran at Fermilab’s Tevatron particle collider for decades and discovered the top quark in 1995.
Today, Canadian institutions and Fermilab collaborate in several ways on the search for particles of dark matter — a substance that composes 26 percent of the universe but has not yet been directly detected. Scientists from the University of Victoria in British Columbia participate in the effort to search for particles of dark matter through Fermilab’s MiniBooNE experiment. And three dark matter experiments that originated at Fermilab have found new homes at Canada’s SNOLAB, a science laboratory operating 2 kilometers underground near Sudbury, Ontario. Theoretical physicists from Fermilab and the Perimeter Institute in Waterloo collaborate toward an ever better understanding of the universe’s underlying principles.
Collaboration between the TRIUMF laboratory and Fermilab was also on display during the Governor General’s tour, including a key component, designed by TRIUMF and built by Canadian company D-Pace, of the particle accelerator upgrades that will generate the neutrino beam for DUNE. Fermilab has also provided particle accelerator and particle detector technology to the Canadian laboratory for research.
“Canadian scientists have collaborated with Fermilab for decades on particle physics research and particle accelerator technology,” Lockyer said. “I look forward to working together and seeing where the next 20 years will take us, both in particle physics technologies and better accelerators for science and society.”