Editor’s note: The PICO-60 detector was originally called “COUPP-60,” with COUPP standing for “Chicagoland Observatory for Underground Particle Physics.” It was designed and built by Fermilab in collaboration with the University of Chicago and Indiana University, South Bend. Work began at Fermilab in 2005, and, after extensive testing, the detector was moved to SNOLAB in 2012.
A team of Fermilab scientists installs the PICO-60 dark matter detector at SNOLAB. Photo: Fermilab
“We’ve been working on this for a long time,” said Fermilab’s project manager Andrew Sonnenschein of the below result. “This is by far our most satisfying result yet, because the techniques we used to reject background events from sources other than dark matter worked flawlessly. Bubble chambers are finally living up to their full potential as dark matter detectors. Now the dark matter just needs to show up.”
Read the original SNOLAB press release on the SNOLAB website.
The PICO Collaboration is excited to announce that the PICO-60 dark matter bubble chamber experiment has produced a new dark matter limit after analysis of data from the most recent run. This new result is a factor of 17 improvement in the limit for spin-dependent WIMP-proton cross-section over the already world-leading limits from PICO-2L run-2 and PICO-60 CF3I run-1 in 2016.
The PICO-60 experiment is currently the world’s largest bubble chamber in operation; it is filled with 45 Liters of C3F8 (octafluoropropane) and is taking data in the ladder lab area of SNOLAB. The detector uses the target fluid in a superheated state such that a dark matter particle interaction with a fluorine nucleus causes the fluid to boil and creates a tell tale bubble in the chamber.
The PICO experiment uses digital cameras to see the bubbles and acoustic pickups to improve the ability to distinguish between dark matter particles and other sources when analysing the data.
The superheated detector technology has been at the forefront of spin-dependent (SD) searches, using various refrigerant targets including CF3I, C4F10 and C2ClF5, and two primary types of detectors: bubble chambers and droplet detectors. PICO is the leading experiment in the direct detection of dark matter for spin-dependent couplings and is developing a much larger version of the experiment with up to 500 kg of active mass.
This work was supported by the the U.S. Department of Energy Office of Science and the U.S. National Science Foundation under Grants PHY-1242637, PHY-0919526, PHY-1205987 and PHY-1506377, and in part by the Kavli Institute for Cosmological Physics at the University of Chicago through grant PHY-1125897, and an endowment from the Kavli Foundation and its founder Fred Kavli. The PICO Collaboration would also like to acknowledge the support of the National Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI) for funding.
Inside the PICO-60 detector, installed at SNOLAB in Sudbury, Ontario. Photo: SNOLAB
About PICO
17 participating institutions: University of Alberta; University of Chicago; Czech Technical University; Fermilab; Indiana University South Bend; Kavli Institute for Cosmological Physics; Laurentian University; Université de Montréal; Northeastern Illinois University (NEIU); Northwestern University; Universidad Nacional Autonoma de Mexico; Pacific Northwest National Laboratory; Queen’s University at Kingston; Saha Institute of Nuclear Physics, India; SNOLAB; Universitat Politecnica de Valencia; Virginia Tech.
The PICO Collaboration (formed from the merger of two existing groups, PICASSO and COUPP) uses bubble chambers and superheated fluid to search for dark matter. The PICO-60 detector consists of a fused-silica jar sealed to flexible, stainless steel bellows, all immersed in a pressure vessel filled with hydraulic fluid. Eight lead zirconate (PZT) piezoelectric acoustic transducers mounted to the exterior of the bell jar record the acoustic emissions from bubble nucleation and four 2-megapixel resolution fast CMOS cameras are used to photograph the chamber. The PICO-60 detector was built at Fermilab in Batavia, IL and installed underground at SNOLAB in 2012.
The PICO bubble chambers are made insensitive to electromagnetic interactions by tuning the operating temperatures of the experiment, while the alpha decays are discriminated from dark matter interactions by their sound signal, making these detectors very powerful tools in the search for dark matter.
PICO is operating two detectors deep underground at SNOLAB: PICO-60, a bubble chamber with 52 kg of C3F8 and PICO-2L, another bubble chamber with 2.9 kg of C3F8.
The paper is available on the arXiv.
About SNOLAB
SNOLAB is Canada’s leading edge astroparticle physics research facility located 2 km (6800 ft) underground in the Vale Creighton Mine. The SNOLAB facility was created by an expansion of the underground research areas next to the highly successful Sudbury Neutrino Observatory (SNO) experiment. The entire laboratory is operated as an ultra-clean space to limit local radioactivity. With greater depth and cleanliness than any other international laboratory, it has the lowest background from cosmic rays providing an ideal location for measurements of rare processes that would be otherwise unobservable.
Learn more
Quotes:
“PICO bubble chambers provide the best discrimination against backgrounds of any dark matter detector technology. This pretty much guarantees a continued improvement of sensitivity in upcoming chamber designs. We are still very far from reaching the limits of this technique.”
Juan I. Collar
U.S. spokesperson
Department of Physics
Enrico Fermi Institute
Kavli Institute for Cosmological Physics
“We are extremely excited about these results. Not only have we established a new world-leading limit for dark matter interactions, but we have also demonstrated that with sufficient controls the bubble chamber technology can be run free of backgrounds that could mimic the signal. This bodes very well for the future, as the collaboration is poised to launch a new tonne scale detector based on this technology. This new detector, dubbed PICO 500, will have an order of magnitude greater physics capability and will explore a vast swathe of the parameter space predicted by dark matter theories.”
Tony Noble
Canadian spokesperson
Department of Physics
Queen’s University
For more information, please contact:
Samantha Kuula
Communications officer, SNOLAB
Phone: 705-692-7000 ext. 2222
Email: Samantha.Kuula@snolab.ca
Website: www.snolab.ca
French language contact:
Guillaume Giroux
Postdoctoral fellow, Queen’s University
Email: ggiroux@owl.phy.queensu.ca
Phone: 613-533-6000 ext. 79203
U.S. contact:
Andrew Sonnenschein
Project manager, PICO-60
Fermi National Accelerator Laboratory
Email: sonnensn@fnal.gov
Phone: 630-840-2883
Among other tasks, Computing’s Keith Coiley has task-managed the installation of the tape robot system at the Feynman Computing Center. Photo: Reidar Hahn
How long have you been at Fermilab?
I started as a part-time employee the summer of 1969 on my 17th birthday. You had to be 17 to work out here at the time. It was the end of my junior year of high school.
I worked here again the following summer and then found out there were openings at receiving. So I went to work in that department full-time. That was May 1971, and I’ve been here ever since.
What do you do as a data center specialist in computing?
I’m kind of a one-stop shop where computing folks can call with whatever need they have. It’s a pretty broad range: tape robot system installation, fire suppression systems, deliveries, small construction jobs.
I also organize staff moves that are tied to the computing sector. All someone has to do is pack their stuff, and I have everything else taken care of: set up where they’re going, move phones, take care of furniture needs. I’m a people person, and I try to bring a calming effect to different folks who are stressed by having to move offices. I’m here to make this as easy as possible for them.
When do you use your people skills?
One time Lisa Carrigan [who works in Wilson Hall building management] told me they were going to get rid a lot of their steel case panels on the 12th floor. Well, on the eighth floor, which was staffed with computing folks, all we had were cabinets that separated the offices. I took those panels and made arrangements to have everything in a nice cubicle setup.
One hitch: The day we were going to do the install, the Italian prime minister was coming to the lab. There was no way we were going to be able to use the elevators. Brian Niesman [who works in transportation] said, “I think I have way we can take care of this.” He had a couple of guys stay that night to get all these panels to the eighth floor, so we were able to get it done.
That’s what I mean about having relationships with other areas outside our divisions. We help each other.
What do you enjoy about working at Fermilab?
When I first came out here, I had no idea what the lab was going to be. It was a job. But Fermilab became such an education. It was like working at a little UN in the middle of nowhere. To meet people from all over the world, learn about different cultures, make friendships — it’s been really amazing.
What do you do outside the lab?
I fish. Some of the best fishing around is out here at the lab.
I spend a lot of my time with my grandkids — three of them, and one on the way. My youngest one was a Gerber baby.
What’s something that people may not know about you?
The second summer I worked here, my plan was to just make some money and go to New York for the theater. And as you can see, 46 years later, I’m still here. I have fun acting in my church’s theater group. The plays are really some very nice productions.
Two years ago, my wife took a business trip to Zurich, and I tagged along. We found our way to the LHC and saw the CMS detector, thanks to [Fermilab CIO] Rob Roser. That was great to see.
The neutrino, it would seem, has global appeal.
The mysteries surrounding the renegade particle are attracting a worldwide science community to the future DUNE experiment. DUNE — the Deep Underground Neutrino Experiment — is a multinational effort to address the biggest questions in neutrino physics. More than 950 researchers from 30 countries have joined the DUNE collaboration, and both numbers are trending upward: Back in 2015, the collaboration comprised about 560 scientists and engineers from 23 countries.
It’s currently the largest particle physics project being undertaken anywhere in the world since the Large Hadron Collider at the European laboratory CERN. Modeled after CERN’s ATLAS and CMS experiments, the DUNE collaboration is an international organization. The experiment will be hosted in the United States by Fermi National Accelerator Laboratory.
The latest countries to join DUNE include Chile and Peru. The most recent new institutes to join DUNE come from Colombia, the UK and the US.
“It’s the excitement that’s being generated by the science,” said DUNE spokesperson Mark Thomson, a professor of physics at the University of Cambridge in the UK. “Everybody recognizes the DUNE program as strong, and the technology is interesting as well.”
It’s a tall order that will take a global village to fill, and researchers worldwide are currently building or signing up to build the experiment, taking advantage of DUNE’s broad scientific and geographic scope.
“We’re a country that does a lot of theoretical physics but not a lot of experimental physics, because it’s not so cheap to have a particle physics experiment here,” said Brazilian DUNE collaborator Ana Amelia Machado, a collaborating scientist at the University of Campinas and a professor at the Federal University of ABC in the ABC region of Brazil. “So we participate in big collaborations like DUNE, which is attractive because it brings together theorists and experimentalists.”
Machado is currently working on a device named Arapuca, which she describes as a photon catcher that could detect particle phenomena that DUNE is interested in, such as supernova neutrino interactions. She’s also working to connect more Latin American universities with DUNE, such as the University Antonio Nariño.
On the opposite side of the world, scientists and engineers from India are working on upgrading the high-intensity proton accelerator at Fermilab, which will provide the world’s most intense neutrino beam to the DUNE experiment. Building on the past collaborations with other Fermilab experiments, the Indian scientists are also proposing to build the near detector for the DUNE experiment. Not only are India’s contributions important for DUNE’s success, they’re also potential seeds for India’s own future particle physics programs.
More than 950 researchers from 30 countries have joined DUNE. Collaborators are developing new technologies for DUNE’s particle detectors, giant instruments that will help capture the notoriously elusive neutrino.
“It’s exciting because it’s something that India’s doing for the first time. India has never built a full detector for any particle physics experiment in the world,” said Bipul Bhuyan, a DUNE collaborator at the Indian Institution of Technology Guwahati. “Building a particle detector for an international science experiment like DUNE will bring considerable visibility to Indian institutions and better industry-academia partnership in developing advanced detector technology. It will help us to build our own future experimental facility in India as well.”
DUNE’s two particle detectors will be separated by 800 miles: a two-story detector on the Fermilab site in northern Illinois and a far larger detector to be situated nearly a mile underground in South Dakota at the Sanford Underground Research Facility. Fermilab particle accelerators, part of the Long-Baseline Neutrino Facility for DUNE, will create an intense beam of neutrinos that will pass first through the near detector and then continue straight through Earth to the far detector.
Scientists will compare measurements from the two detectors to examine how the neutrinos morphed from one of three types into another over their interstate journey. The far detector will contain 70,000 tons of cryogenic liquid argon to capture a tiny fraction of the neutrinos that pass through it. DUNE scientists are currently working on ways to improve liquid-argon detection techniques.
The near detector, which is close to the neutrino beam source and so sees the beam where it is most intense, will be packed with all kinds of components so that scientists can get as many readings as they can on the tricky particles: their energy, their momentum, the likelihood that they’ll interact with the detector material.
“This is an opportunity for new collaborators, where new international groups can get involved in a big way,” said Colorado State University professor Bob Wilson, chair of the DUNE Institutional Board. “There’s a broad scope of physics topics that will come out of the near detector.”
“There aren’t that many new, big experiments out there,” Thomson said. “We have 950 collaborators now, and we’re likely to hit 1,000 in the coming months.”
That will be a notable milestone for the collaboration, one that follows another sign of its international strength: Late last month, for the first time, DUNE held its collaboration meeting away from its home base of Fermilab. CERN served as the meeting host.
DUNE is supported by funding agencies from many countries, including the Department of Energy Office of Science in the United States.
“We have people from different countries that haven’t been that involved in neutrino physics before and who bring different perspectives,” Wilson said. “It’s all driven by the interest in the science, and the breadth of interest has been tremendous.”
Fermilab’s Scott Borton stands in front of shelves full of old scientific equipment. Many of these items will be put to future use through the Laboratory Equipment Donation Program. Photo: Dan Garisto
If you’re a scientist looking for a bargain on a UV lamp source, CompuFlow thermo-anemometer, miscellaneous fiber optic components or an oscilloscope, Fermilab has you covered.
At the lab’s Warehouse No. 2, racks piled high with items stretch into the distance. When equipment at Fermilab is no longer needed, it’s picked up and stored here, where much of it is processed and sent to schools, universities and government agencies who request it.
The whole operation is run by Scott Borton, who oversees three separate initiatives at Fermilab: Computers for Learning, the Federal Disposal System and the Laboratory Equipment Donation Program (LEDP). Between 2015 and 2017, the total value of assets donated through all three programs was over $3,000,000.
For Fermilab, it’s a great way to extend the life of equipment that’s come to the end of its usefulness for the laboratory. And for prospective buyers, it’s hard to imagine a better deal.
“This is all free. They pay for shipping and that’s it,” Borton said.
Designed to reduce waste and provide opportunities for schools, labs and agencies lacking the funds, the programs are well-used at Fermilab, with items sent to Borton on a regular basis.
Fermilab employees send to the warehouse old or underused equipment that they no longer need. Plenty of items come through the warehouse, so it’s not always clear what the status of this equipment is.
“In a lot of the cases, the equipment’s been moved and transferred so often that nobody has any idea if it works or not,” Borton said.
When this happens, Borton and his staff often draw on the experience of Fermilab’s experts to determine the status of equipment to make sure it’s in working condition.
Although the equipment is used, the zero on the price tag is enticing for physics professors such as Raul Armendariz, who teaches at Queensborough Community College in New York City. Armendariz learned about LEDP and arranged for the equipment transfer through Fermilab’s QuarkNet program.
“Getting the laboratory equipment is so important,” Armendariz said. “It allows us to build detectors and create projects for students and have them take part in the learning community.”
In December, Armendariz used the nationwide LEDP program to purchase — at no cost — 1,800 pounds of plastic scintillator scavenged from Fermilab’s CDF detector, which was decommissioned in 2013. He plans to use the scintillator to set up a cosmic ray array at local high schools and colleges in New York City.
“We’re at a community college and we don’t have big money for this kind of stuff — that’s why the LEDP is crucial for us,” Armendariz said.
For Borton, recycling what was once state-of-the-art equipment to schools and other labs is just another day at work.
“At least the stuff isn’t going to scrap,” he said. “It’s being reused somewhere.”
The SIGNA PET MR from GE Healthcare is one of the many systems that will be updated to HELiOS in the coming 2 years. Image Image: GE Healthcare
What does running large particle accelerators have in common with hospital imaging scanners? The operating system for both requires high performance and stability.
Fermilab first developed Scientific Linux as an open-source operating system in 2004 to fulfill exactly these demands, and it continues to release new versions.
GE Healthcare, a company that builds medical imaging equipment, found that it had the same needs when it came to operating systems. It now employs Scientific Linux as a foundation for its own, customized HELiOS, which stands for Healthcare Enterprise Linux Operating System.
According to GE, more than 30,000 medical imaging machines worldwide use this SL-based operating system to search for broken bones, tumors and other injuries on organs, and their numbers will easily double in the next two years. On GE machines, HELiOS manages the whole process, from taking an image of a patient to reconstructing the image and even displaying it for doctors.
At Fermilab, Scientific Linux runs on all computers for particle accelerator operation and on most data taking systems for experiments. Many scientists use it every day to write simulations or perform data analysis.
“Originally we created Scientific Linux for the high-energy physics community, but it was never exclusively for them. Everybody can download and use it,” said Connie Sieh, Fermilab computer specialist and co-developer of Scientific Linux. “We were really surprised when GE contacted us. We had never expected that our SL would spread that far or that it would be used in medicine.”
GE initiated the contact with Fermilab about the software, discussing customization issues. From there, the two institutions began a regular, informal exchange of knowledge and ideas to improve both operating systems.
Fermilab uses Scientific Linux to control and monitor all accelerators on site from the main accelerator operations room. Photo credit: Reidar Hahn
“Now we talk and meet on a regular basis, which is great, and Fermilab assistance is very welcome,” said James Foris, senior system engineer at GE Healthcare. “This exchange really reflects the open-source mentality we all share in software development.”
Fermilab develops Scientific Linux in the same way most Linux distributions are developed: The source code is freely available and can be changed or customized. Fermilab’s computing experts continually customize the Red Hat Linux distribution to provide a stable, scalable and extensible operating system to support the needs of the scientific community. GE then leverages Fermilab’s Scientific Linux to create HELiOS, a Linux distribution for healthcare applications.
“We use this style of software development for our products to ensure that our customers get a stable system tailored to their needs,” Foris said. “And avoiding the extra costs for software licenses always helps.”
One other attractive feature of Scientific Linux is its long lifespan: A single SL version, such as SL version 7, is supported by updates for 10 years. (A quick lesson in new versions versus new updates: Installing a new version, say version 7, is like buying a new car, while updating a version, say from version 7 to 7.1, is like getting an oil change or new tires. An update includes some new features, but never a major change in the whole design of the software. Major changes are released as new versions, such as SL version 8.)
For GE, this long lifespan means that they can support the software of their magnetic resonance imagers and other systems for 10 years, providing publicly reviewed and available bug fixes and security updates, without making major changes, which can be inconvenient for their customers.
Fermilab’s computing experts increase the security of the operating system to fulfill the standards of usage at a Department of Energy national laboratory. They implement features for easy access to file sharing and data storage, which are crucial for high-performance computing. GE uses those computing features for their own image reconstruction.
Scientific Linux was created for running accelerators and calculating particle collisions, and now its use has extended to our everyday lives, assisting people worldwide with their health and well-being.
The Scientific Linux team wishes to thank Red Hat for its contributions to maintaining an open, free, collaborative, and transparent open source community for software development.