Scientists working at CERN have started tests of a new neutrino detector prototype, using a very promising technology called “dual phase.” If successful, this new technology will be used at a much larger scale for the international Deep Underground Neutrino Experiment, hosted by the U.S Department of Energy’s Fermilab.
Scientists began operating the dual-phase prototype detector at CERN at the end of August and have observed first tracks. Filled with 800 tons of argon, the detector is about the size of a three-story house.
The new technology would be used in addition to so-called single phase detectors that have been successfully operated during many years. But the new dual-phase technology may be game-changing, as it would significantly amplify the faint signals that particles create when moving through the detector.
This picture shows a track made by a cosmic-ray muon observed in the dual-phase ProtoDUNE detector. The ionization released by the muon track in liquid argon and by the correlated electromagnetic activity can be seen. Image: ProtoDUNE
“The single-phase technology is a proven method that will be used to build the first module for the DUNE detector,” said DUNE co-spokesperson Ed Blucher of the University of Chicago. “This new dual-phase technology provides a second method that has great potential to add to the DUNE detector’s capabilities.”
In a single-phase experiment, the particle detector is filled entirely with liquid argon. Wire planes and photo sensors submerged in the liquid argon record the faint signals caused when a neutrino smashes into an argon atom. The DUNE collaboration successfully began operating a large single-phase prototype detector at CERN in September 2018.
Scientists and engineers have now deployed on a large scale a dual-phase technology that uses liquid argon as target material and a layer of gaseous argon above the liquid to amplify faint particle signals before they arrive at sensors located at the top of the detector, inside the argon gas. Compared to the single-phase technology, this setup could yield stronger signals, which makes them stand out from background noise. It would thus enable scientists to look for lower-energy neutrino interactions.
Another advantage of the dual-phase technology: All the electronics for the data collection are located in the gas layer near the top of the detector and can be accessed via special chimneys that open from the outside, even as most of the detector is filled with argon, kept at a temperature below minus 184 degrees Celsius (minus 300 degrees Fahrenheit).
In contrast to the single-phase technology, the detector features a single active volume with no detector components in the middle of the liquid argon and a reduced number of readout elements at the top.
“This is a very elegant design that requires advances in high-voltage technology and argon purity,” said Fermilab Director Nigel Lockyer.
The prototype is a cube-shaped detector that is about six meters long in each direction. The collection of the electrons and readout of the signals is performed by innovative systems, each with a surface of nine square meters, individually suspended a few millimeters above the liquid level.
The dual-phase ProtoDUNE detector is but a small component of the detector the international DUNE collaboration plans to build in the United States over the next decade: a DUNE detector module will house the equivalent of 20 dual-phase prototype detectors and operate at a high voltage of up to 600,000 volts.
DUNE plans to build four full-size detector modules based on argon technology. They will be located a mile underground at the Sanford Underground Research Facility in South Dakota. Scientists will use it to discover whether neutrinos could be the reason that matter dominates over antimatter in our universe.
The outcomes of the test at CERN will help with the decision how many modules will feature the single-phase technology and how many will use the dual-phase technology.
The DUNE collaboration includes more than 1,000 scientists and engineers from over 30 countries in five continents: Africa, Asia, Europe, North America and South America.
Preparing Sanford Underground Research Facility (Sanford Lab) for its role as the far site for the largest physics experiment on United States soil demands a sizeable workforce: the Fermi National Accelerator Laboratory Long-Baseline Neutrino Facility, or LBNF, team, contractors, and Sanford Lab infrastructure technicians, safety teams and support scientists, just to name a few. All these teams converge in Lead, South Dakota, to ready the facility for the Deep Underground Neutrino Experiment, hosted by Fermilab.
With an increasing underground workforce, LBNF has undertaken multiple projects to ensure worker safety. Working closely with Sanford Lab staff, LBNF recently completed an upgrade to emergency systems, including areas of refuge and evacuation capabilities.
Entrance to the Refuge Chamber on the 4850 Level of Sanford Underground Research Facility. The compressed air management system can be seen to the left of the door. The Refuge Chamber can shelter 144 people in case of an underground emergency. Photo: Nick Hubbard
“This recent project doubles the number of people that can safely work underground at once, increasing the headcount from 72 to 144 people,” said Mike Headley, executive director of Sanford Lab. “This is a healthy increase that will allow us to support construction for LBNF.”
The main component of this project was the upgrade of the 4850 Level Refuge Chamber, designed to shelter people in case of an underground emergency in which immediate evacuation is not possible. Previously, the Refuge Chamber could provide shelter to 72 people for 96 hours. Now, using a newly installed compressed-air management system, an indefinite supply of breathing air will be available. The team also replaced former carbon dioxide scrubbers with smaller, more efficient scrubbers as a secondary air source.
“With LBNF construction continuing to ramp up, we need greater capacity for workers underground — for the LBNF project as well as all the Sanford Lab maintenance crews and other science collaborations,” said Colton Clark, a Fermilab LBNF engineer who led the Refuge Chamber upgrade. “This project means we can safely bring more workers underground at once.”
Peter Girtz trains a facility guide on new Refuge Chamber procedures. Photo: Nick Hubbard
Engineers also designed new railings for the Yates Shaft Work Deck, allowing the platform to be used in addition to the cage during an emergency evacuation. This upgrade allows for 144 people to evacuate the underground in a timely way.
“Whether people need to take refuge underground or the space needs to be evacuated quickly, these upgrades allow us to ensure their safety in case of an emergency,” said Andrew Brosnahan, the Sanford Lab engineer who designed the Work Deck railings.
“We can expect to see a modest increase in the underground workforce in the near term,” Headley said. “As LBNF starts to see an increase in construction activities in 2020, and certainly as they transition into the main cavern excavation at the end of 2020, we’ll see a noticeable increase in onsite personnel.”
The Refuge Chamber is outfitted with MineARC Systems carbon dioxide scrubbers as a secondary air supply system. Photo: Nick Hubbard
The Deep Underground Neutrino Experiment, or DUNE, will consist of two neutrino detectors placed in the world’s most intense neutrino beam. One detector will record particle interactions near the source of the beam, at Fermilab in Batavia, Illinois. A second, much larger, detector will be installed more than a kilometer underground at Sanford Lab — 1,300 kilometers (800 miles) from Fermilab. These detectors will enable scientists to search for new subatomic phenomena and potentially transform our understanding of neutrinos and their role in the universe.
Fermilab’s Long-Baseline Neutrino Facility will house the neutrino beamline at Fermilab and additional infrastructure and the far-site DUNE detectors at Sanford Lab.
This article was originally published by Sanford Underground Research Facility.
Neutrinos are ubiquitous yet elusive particles that could shed light on the early evolution of the universe. As one of the world’s major laboratories for neutrino physics, Fermilab partners with leading organizations around the globe to get a firmer grasp on these subtle particles.
On Sept. 19, the University of Bern in Switzerland and the Department of Energy’s Fermilab signed an agreement to collaborate on neutrino experiments to be carried out at the laboratory. The agreement is the first such between Fermilab and a Swiss university. It covers the joint research and development of advanced neutrino detectors for three different experiments: MicroBooNE, SBND and the international Deep Underground Neutrino Experiment.
“I am proud of this agreement that witnesses the high quality of our basic research and our competitiveness to take part in collaborations at the highest international level,” said University of Bern Rector Christian Leumann.
On Sept. 19, the University of Bern in Switzerland and Fermilab signed an agreement to collaborate on neutrino experiments to be carried out at the laboratory. Seated, from left: Fermilab Director Nigel Lockyer, University of Bern Rector Christian Leumann, University of Bern scientist and group leader Antonio Ereditato. Standing, from left: Fermilab Chief of Staff Hema Ramamoorthi, Fermilab Office of Partnerships and Technology Transfer Manager Cherri Schmidt, Fermilab Neutrino Division Head Steve Brice, University of Bern Laboratory for High Energy Physics Deputy Director Michele Weber, Fermilab Deputy Director of Administration Tim Meyer, Department of Energy Federal LBNF/DUNE Project Director Pepin Carolan, Department of Energy Associate Director of Science for High Energy Physics Director Jim Siegrist. Photo: Reidar Hahn, Fermilab
DUNE will study neutrinos that are produced at Fermilab, outside Chicago, using its Long-Baseline Neutrino Facility and sent to Lead, South Dakota, 800 miles away. Neutrinos will be measured by a near detector hosted at Fermilab and by a far apparatus at Lead in an underground laboratory at the Sanford Underground Research Facility. This will allow scientists to study neutrino oscillations along the way. DUNE will also be able to detect neutrinos from astrophysical sources and will search for matter instability.
“This agreement brings to Fermilab a novel-design liquid-argon detector,” said Fermilab Director Nigel Lockyer. “What we learn will inform the final design of the DUNE near detector.”
Researchers at the University of Bern conceived, developed and prototyped a detector design, called ArgonCube, for the DUNE near-detector complex. The ArgonCube technology enables the fully spatial reconstruction of neutrino interactions with a novel configuration.
University of Bern researchers are also active in the Short-Baseline Neutrino program at Fermilab, which comprises three neutrino detectors to explore oscillations and search for a hypothesized but never observed particle called sterile neutrino. Bern scientists provided, for the two Short-Baseline Neutrino detectors MicroBooNE and SBND, the UV-laser calibration system and the cosmic-ray tagger detector. The latter in particular allows the identification of particles of cosmic origin. These constitute a serious source of background for neutrino experiments but can be efficiently detected and removed by the cosmic-ray tagger.
“This international agreement is a paradigmatic example representative of the global approach required to meet the challenges of modern neutrino physics projects,” said Bern group leader Antonio Ereditato.
Fermilab’s research is supported by the DOE Office of Science.