On May 12, a delegation from the U.S. House of Representatives Committee on Science, Space and Technology visited the U.S. Department of Energy’s Fermi National Accelerator Laboratory, touring R&D facilities and discussing the laboratory’s flagship neutrino research program. The House Science Committee has jurisdiction over the Department of Energy’s Office of Science, which oversees Fermilab and other national laboratories.
The bipartisan delegation included five members of Congress: Energy Subcommittee Chairman Randy Weber (R-Texas), House Science Committee Vice Chairman Frank Lucas (R-Oklahoma), Representative Bill Foster (D-Illinois), Environment Subcommittee Chairman Andy Biggs (R-Arizona) and Representative Neal Dunn (R-Florida). Science Committee staff members also participated in the tour.
“This is cutting-edge science,” said U.S. Representative Neal Dunn. “The Department of Energy runs 17 of these cutting-edge scientific labs that actually propel our industry as well as our defense and, frankly, our universities. Whole industries have grown up around some of the basic science that has been discovered at these labs.”
The visit kicked off with presentation by Fermilab senior management on the international flagship Long-Baseline Neutrino Facility and Deep Underground Neutrino Experiment and plans for the PIP-II particle accelerator project at the laboratory. Hosted by Fermilab, the LBNF/DUNE project introduces next-generation technology to the worldwide quest to unlock the mysteries of neutrinos, tiny particles that may give us a key to the origin of matter in the universe. More than 1,000 scientists from over 30 countries have come together to design and build the project, which will send an intense beam of neutrinos from Fermilab to gigantic particle detectors at the Sanford Underground Research Facility in South Dakota.
“The technology that’s being developed here, the science that is being created here, is something that is not just going on in the United States; it’s going on around the world,” said Committee Vice Chair Frank Lucas. “If we don’t continue to spend the resources and make the investments to continue to develop the kind of facilities that we have, like the national laboratories, then we won’t be a part of the leading group. We will fall behind, and in a world where technology is an ever more important driving part of the economy, which is everyone’s livelihood, we don’t want to be a second-class nation. That’s why we make the investments. That’s why the Science Committee is here to see what’s going on with our investments, so that we can continue to be a first-rate nation with a first-rate economy, and that requires a first-rate scientific endeavor.”
The delegation then departed on an extensive tour of Fermilab’s world-class facilities, starting with those dedicated to developing and testing advanced superconducting radio-frequency technology for particle acceleration. The laboratory’s expertise in SRF technology is being leveraged for the LCLS-II X-ray laser project at the DOE’s SLAC National Accelerator Laboratory in California, as well as the major PIP-II upgrade of the Fermilab accelerator complex, which will generate the powerful neutrino beams for LBNF/DUNE.
“We want to stay international leaders as far as science and technology, and this really sets a great foundation,” said Environment Subcommittee Chair Andy Biggs. “When the 17 labs work together, that allows us to build on that and be the number one innovative, scientific discovery country in the world. And that’s where we want to be, and that’s where we need to be, both for national security and for economics, but also for pure-science purposes.”
Next on the agenda was a stop at the new Quantum Laboratory. The visitors heard about Fermilab’s application of SRF technology to quantum computing, and the use of quantum technology for particle physics discovery.
“The technologies that are generated here can be used through known and unknown applications of the future,” said U.S. Representative Bill Foster, a former Fermilab scientist. “Superconducting RF obviously has lots of potential applications. Just the idea that you can have a much more efficient particle accelerator opens up a lot of possibilities.”
The representatives and their staff members then met Italian Nobel laureate Carlo Rubbia, who leads the ICARUS neutrino experiment at Fermilab. Together they congratulated the graduates of Fermilab’s Saturday Morning Physics program.
“We had about 100 students from the suburbs and Chicago Public Schools graduate from this session of Saturday Morning Physics,” said Fermilab Director Nigel Lockyer. “This is one of our most successful STEM outreach programs that has introduced high students to particle physics for over 35 years. The students were thrilled to meet Carlo and the members of Congress.”
A stop at the Muon g-2 experiment was followed by a tour of a cavern 350 feet underground that houses the MINERvA and NOvA neutrino experiments and the SENSEI detector, a prototype for a new technology to search for dark matter particles.
“Fermilab brings scientists from around the world to Illinois to do world-leading science in many areas, from neutrinos to muons to quantum research,” said U.S. Representative Randy Hultgren, whose district includes Fermilab but who was unable to attend the May 12 visit due to family obligations. “The lab is a crucial resource to Illinois’s people and economy and to the entire country. I look forward to even greater things to come now that the Deep Underground Neutrino Experiment and construction of the Long-Baseline Neutrino Facility are under way at Fermilab and in South Dakota.”
The final stop on the tour showcased Fermilab’s involvement and leadership role at the CMS experiment at the European research center CERN’s Large Hadron Collider. Fermilab facilitates the participation by hundreds of scientists at institutions across the United States in the CMS experiment.
“This is my first trip to Fermilab; won’t be my last,” said Energy Subcommittee Chair Randy Weber. “We understand this accelerator research they are doing, the neutrino beam research they are doing, is unbelievable. So when we look at the kind of processes that they are developing, we want to be the world leader, it helps in so many directions that we are impressed. Very, very impressive.”
Congressman Randy Weber, chair of the Energy Subcommittee of the House Science Committee, congratulated about 100 Saturday Morning Physics students at their graduation ceremony when he and four other members of the House Science Committee visited Fermilab on May 12, 2018. From left: Fermilab Director Nigel Lockyer, Nobel laureate Carlo Rubbia, Congressman Bill Foster, D-Illinois, Congressman Randy Weber, R-Texas, Congressman Frank Lucas, R-Oklahoma; Congressman Andy Biggs, R-Arizona; Congressman Neal Dunn, R-Florida. Photo: Reidar Hahn
Fermilab’s Muon g-2 experiment, which examines muons — short-lived particles that could open a window on possible sources of new physics — has elected Mark Lancaster to help lead it into the next stage of exploration. Lancaster, professor of physics at University College London and, beginning in September, the University of Manchester, will assume the role in early July.
Lancaster instigated the UK’s involvement in the Muon g-2 experiment five years ago and since has helped lead the design and construction of one of the Fermilab experiment’s two particle detector systems. He now takes the helm to co-lead the experiment itself, along with current Muon g-2 co-spokesperson and Fermilab scientist Chris Polly.
“Mark has played a vital role in building up the international collaboration,” Polly said. “As he takes on this leadership role, he’ll help bring a fresh, independent perspective at a time when the experiment has to be at its most introspective, moving towards our first physics result.”
Lancaster succeeds former co-spokesperson David Hertzog, physicist at the University of Washington. Lancaster and Polly say they are grateful for Hertzog’s impressive work on Muon g-2, overseeing some of the most crucial periods in its development.
“Dave has done an outstanding job leading the collaboration from the proposal stage, through construction and commissioning, and now to the point where the experiment is taking physics-quality data,” Polly said.
Muon g-2 scientists are measuring a property of the muon — a heavy cousin of the electron — called its magnetic moment. Departures from the predicted value of this property could point to new physics, including the existence of undiscovered particles or new forces, and pave the way for future experiments.
“At the moment, Muon g-2 is entering a very exciting time — we’ve just started our first major data collection period here at Fermilab,” Lancaster said.
At Muon g-2, muons travel through a large, 50-foot-wide particle storage ring with a strong magnetic field. As the beam of muons circles around the ring, they act like tiny, spinning magnets. Within the ring, the muon’s spin direction rotates around its axis — like a gyroscope — in response to the magnetic field. The muons subsequently decay, producing particles whose direction of travel is directly related to the muon’s magnetic moment. The amount the magnetic moment differs from predictions is due to virtual particles popping in and out of the vacuum.
The Fermilab experiment, a collaboration of over 25 institutions and almost 200 physicists and engineers, recently began the first of three year-long data-taking runs. It picks up where the Brookhaven National Laboratory Muon g-2 experiment left off. In 2001, Brookhaven first reported a discrepancy between the predicted and measured values of the magnetic moment. The storage ring was relocated to Fermilab in 2013. Now that the experiment has begun taking data, the goal at Fermilab is to collect 20 times the amount of data with four times the precision compared to Brookhaven.
“We’re currently seeking to measure the muon’s magnetic moment with a far greater precision than previously achieved,” Lancaster said. “By taking more data and reducing the systematic uncertainties in the measurement, we hope to conclusively confirm or refute the Brookhaven measurement.”
Lancaster says he’s excited to help lead the significant and potentially groundbreaking research for Muon g-2 and to work with a diverse range of scientists and engineers.
“What I look forward to most is working with all of the young people on the experiment who will have smart, new ideas for the way we analyze the data,” Lancaster said. “New approaches for analyzing the data will be invaluable in achieving our goal to solve the longstanding puzzle of the muon’s magnetic moment.”
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.