A Technical Division team rallies around a dressed cavity from the LCLS-II project. Photo: Reidar Hahn
Members of Fermilab’s Technical Division are working on superconducting radio-frequency cavities that are shaped like squatty beads on straight string. These prone, uniformly bulging tubes accelerate the particle beams that shoot through their hollow insides. The team recently achieved a record-high quality factor with a fully dressed cavity for a SLAC-headed project, Linac Coherent Light Source II.
“This has taken a lot of hard work from a very dedicated crew,” said Rich Stanek, Fermilab LCLS-II senior team leader. Stanek acknowledged the entire cavity dressing team and all of the SRF scientists that helped reach this record quality factor.
Quality factor, Q, is a measure of how efficient a particle acceleration cavity is. A higher Q means a cavity is losing less energy, which is more cost-effective.
The two LCLS-II free-electron lasers will produce X-rays to probe a wide variety of materials, exotic and otherwise, at the nanoscale. Fermilab is responsible for designing, developing, building and testing about 150 nine-cell cavities for the LCLS-II superconducting accelerator. The R&D process began one and a half years ago. It includes ensuring that the cavities meet certain Q values during testing.
“This is the first integrated test we did,” said Nikolay Solyak, project support group leader. In an integrated test, everything is checked under real conditions. “The conditions were very close to the cavity’s final condition in a cryomodule.”
In this integrated test, the fully dressed 1.3-gigahertz cavity’s quality factor was 3.1 x 1010 at 2 Kelvin and at a 16-megavolt-per-meter peak surface electric field. This Q exceeds LCLS-II’s goal of 2.7 x 1010 and far surpasses current state-of-the-art standards.
An LCLS-II-type accelerator cavity prepares to be treated with nitrogen, a process that increases the cavity’s quality factor. Fermilab recently reported a record quality factor for LCLS-II-type cavities. Photo: Reidar Hahn
“This quality factor is an extremely important step,” said Slava Yakovlev, SRF department head. “It’s a victory.”
SLAC physicist Marc Ross, LCLS-II cryogenics systems manager, says he’s pleased with the results.
“It’s definitely a victory,” Ross said. “These are some of the highest-quality-factor practical resonators ever built.”
A fully dressed cavity is outfitted with all the components it will wear in the LCLS-II accelerator. This includes a titanium jacket filled with liquid helium chilled to 2 Kelvin, a temperature at which niobium is superconducting. It’s also furnished with power-providing couplers, cavity-squeezing tuners to control frequency, and magnetic shielding. These components add heat and can lower Q, so the team had to develop a way to carry this heat away and keep Q high.
“This record Q is really the sum, the final point, of many years of research,” said Anna Grassellino, Fermi’s Technical Division scientist who leads cavity testing and processing for LCLS-II. “It’s really a miracle of science and technology and engineering coming together and producing an unprecedented quality factor. It opens up a way for machines to operate much more efficiently at a much lower cost.”
Grassellino led the Fermilab effort to apply the breakthrough technology, dubbed nitrogen doping, that helped achieve this record Q. It involves infusing nitrogen into a cavity’s inner niobium surface. Nitrogen doping and other Fermilab discoveries that led to this Q value, such as the removal of magnetic flux through rapid cooling, will become new standards for achieving highly efficient accelerators worldwide.
“This is a critical milestone not only in LCLS-II design, but in other modern accelerator projects including our own project, PIP-II,” Yakovlev said.
But there’s more to be done for LCLS-II.
“We still need to show that the full cryomodule with eight cavities meets specifications,” Grassellino said. “There’s always a next step.”
This display shows neutrino event candidates in the MicroBooNE detector. Image: MicroBooNE
“It’s nine years since we proposed, designed, built, assembled and commissioned this experiment,” said Bonnie Fleming, MicroBooNE co-spokesperson and a professor of physics at Yale University. “That kind of investment makes seeing first neutrinos incredible.”
After months of hard work and improvements by the Fermilab Booster team, on Oct. 15, the Fermilab accelerator complex began delivering protons, which are used to make neutrinos, to one of the laboratory’s newest neutrino experiments, MicroBooNE. After the beam was turned on, scientists analyzed the data recorded by MicroBooNE’s particle detector to find evidence of its first neutrino interactions.
“This was a big team effort,” said Anne Schukraft, Fermilab postdoc working on MicroBooNE. “More than 100 people have been working very hard to make this happen. It’s exciting to see the first neutrinos.”
MicroBooNE is funded by the U.S. Department of Energy. Its detector is a liquid-argon time projection chamber. It resembles a silo lying on its side, but instead of grain, it’s filled with 170 tons of liquid argon.
Liquid argon is 40 percent denser than water, and hence neutrinos are more likely to interact with it. When an accelerator-born neutrino hits the nucleus of an argon atom in the detector, its collision creates a spray of subatomic particle debris. Tracking these particles allows scientists to reveal the type and properties of the neutrino that produced them.
Neutrinos have recently received quite a bit of media attention. The 2015 Nobel Prize in physics was awarded for neutrino oscillations, a phenomenon that is of great importance to the field of elementary particle physics. Intense activity is under way worldwide to capture neutrinos and examine their behavior of transforming from one type to another.
Neutrino scientists in Fermilab’s Remote Operations Center West anticipate first beam in MicroBooNE’s detector. Photo: Reidar Hahn
MicroBooNE is an example of a new liquid-argon detector being developed to further probe this phenomenon while reconstructing the particle tracks emerging from neutrino collisions as finely detailed three-dimensional images. Its findings will be relevant for the forthcoming Deep Underground Neutrino Experiment, known as DUNE, which plans to examine neutrino transitions over longer distances and a much broader energy range. Scientists are also using MicroBooNE as an R&D platform for the large DUNE liquid-argon detectors.
“Future neutrino experiments will use this technology,” said Sam Zeller, Fermilab physicist and MicroBooNE co-spokesperson. “We’re learning a lot from this detector. It’s important not just for us, but for the entire neutrino community.”
In August, MicroBooNE saw its first cosmic ray events, recording the tracks of cosmic ray muons. The recent neutrino sighting brings MicroBooNE researchers much closer to one of their scientific goals, determining whether the excess of low-energy events observed in a previous Fermilab experiment was the footprint of a sterile neutrino or a new type of background.
Before they can do that, however, MicroBooNE will have to collect data for several years.
During this time, MicroBooNE will also be the first liquid-argon detector to measure neutrino interactions from a beam of such low energy. At less than 800 MeV (megaelectronvolts), this beam produces the lowest-energy neutrinos to be observed with a liquid-argon detector yet.
MicroBooNE is part of Fermilab’s Short-Baseline Neutrino program, and scientists will eventually add two more detectors (ICARUS and the Short-Baseline Near Detector) to its neutrino beamline.
The MicroBooNE collaboration includes more than 150 scientists from 28 institutions in five countries.
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. Visit Fermilab’s website at www.fnal.gov, and follow us on Twitter at @Fermilab.
The DOE 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.
Physicists looked at gobs of data on planetary orbits to look for tiny anomalies that couldn’t be explained by either Isaac Newton’s theory of gravity — in which gravity is a force between objects that depends on their masses — or Einstein’s general relativity theory, which says gravity is a warping of space-time itself.
Data collected at the NOvA far detector in northern Minnesota shows one of the first interactions captured at that detector from a beam of man-made neutrinos. The neutrino beam is generated at Fermilab in Illinois and then sent through 500 miles of earth to the far detector. Image courtesy of NOvA collaboration.
In a landmark study, scientists at Delft University of Technology in the Netherlands reported that they had conducted an experiment that they say proved one of the most fundamental claims of quantum theory — that objects separated by great distance can instantaneously affect each other’s behavior.
The finding is another blow to one of the bedrock principles of standard physics known as “locality,” which states that an object is directly influenced only by its immediate surroundings. The Delft study, published Wednesday in the journal Nature, lends further credence to an idea that Einstein famously rejected. He said quantum theory necessitated “spooky action at a distance,” and he refused to accept the notion that the universe could behave in such a strange and apparently random fashion.
Editor’s note: The following news release about the proposed LBNF/DUNE project was issued by the U.S. Department of Energy and is being hosted on the Fermilab website on its behalf.
This graphic illustrates the proposed LBNF/DUNE project, which will include construction at Fermilab in Illinois and at Sanford Lab in South Dakota. Image: Fermilab
A U.S. Department of Energy (DOE) environmental study has determined that building and operating the proposed Long Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) will not have a significant impact on the environment. LBNF/DUNE would help to advance our understanding of the basic physics of the elementary particles called neutrinos and thereby help us to understand the physical nature of our universe.
DOE is following the National Environmental Policy Act of 1969, which requires that the environmental impacts of any federal project must be studied. DOE explored a number of potential impacts in the draft Environmental Assessment (EA), including impacts on people and the environment, from building and operating the research machine. Impact to floodplains and wetlands were also considered. None were considered major, so a Finding of No Significant Impact (FONSI) was issued. Additionally, a Programmatic Agreement (PA), prepared pursuant to the National Historic Preservation Act would put procedures in place to ensure the protection of historic properties. Copies of the final EA and FONSI are available.
DOE started the environmental study on the LBNF/DUNE project by holding informational meetings for the public in Illinois and South Dakota. A draft EA was then prepared and DOE once again conducted public meetings to hear comments on that document. An existing high-energy particle accelerator at Fermilab in Batavia, Illinois will generate neutrinos, analyze them, and then direct them at a detector to be constructed 800 miles away about a mile below ground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota.
Above-ground and below-ground facilities will be constructed at both locations, although at SURF nearly all construction and operations will be underground. In South Dakota, construction for the project could begin in 2017, if funding becomes available, with construction in Illinois to follow in subsequent years.
People interested in reviewing, downloading or requesting a copy of the final EA, which also includes the public comments, DOE responses, the FONSI, and the PA, should visit this url: http://lbnf.fnal.gov/env-assessment.html
For information on the LBNF/DUNE activities, contact:
Mr. Michael J. Weis, Manager
U.S. Department of Energy, Fermi Site Office
P.O. Box 2000, Batavia, IL 60510
Telephone: 630-840-3281
e-mail: michael.weis@science.doe.gov
For general information concerning DOE’s NEPA process, contact:
Mr. Peter R. Siebach, NEPA Compliance Officer
U.S. Department of Energy (STS)
9800 S. Cass Avenue, Argonne, IL 60439
Telephone: 630-252-2007
e-mail: peter.siebach@science.doe.gov.
DOE support of this project comes from its Office of Science’s Office of High Energy Physics.