A groundbreaking ceremony will be held tomorrow to celebrate the start of civil engineering work for a major upgrade to the Large Hadron Collider at CERN in Geneva, Switzerland. When complete, the High-Luminosity LHC (HL-LHC) will produce five to seven times more proton-proton collisions than the currently operating LHC, powering new discoveries about our universe.
For the last decade, scientists, engineers and technicians from the U.S. Department of Energy’s Fermi National Accelerator Laboratory have been working with partners around the world to conduct R&D on new accelerator components that would make operations at the HL-LHC possible. The U.S. research was conducted via the LHC Accelerator Research Program, or LARP. Now the research turns into reality, as construction of the new components begins.
The primary components contributed by the United States for the HL-LHC construction are powerful superconducting magnets and superconducting deflecting cavities, called crab cavities of a novel compact design never before used in an accelerator.
“This is a truly major milestone for the whole U.S. accelerator community,” said Fermilab scientist Giorgio Apollinari, who leads the DOE Office of Science-funded U.S. HL-LHC Accelerator Upgrade Project (AUP). “More than 10 years of research work funded by DOE under LARP have gone into developing these cutting-edge magnets and crab cavities and in demonstrating their technical feasibility for the intended application at HL-LHC. We now look forward with much anticipation to shipping the first components to CERN and seeing them operate as part of the world’s foremost particle collider.”
Fermilab is developing magnets such as this one, which is mounted on a test stand at Fermilab, for the High-Luminosity LHC. Photo: Reidar Hahn
In the LHC, superconducting quadrupole magnets focus the beams into collision at four points around the 27-kilometer ring. In the HL-LHC, these focusing magnets must be more powerful to focus the stream of particles much tighter than in the LHC. Fermilab, in collaboration with DOE’s Brookhaven and Lawrence Berkeley national laboratories, developed the basic technology for these new magnets through LARP. The final design was completed in collaboration with CERN for application in the HL-LHC upgrade.
These new magnets are made of a niobium-tin alloy that allows the magnets to reach the desired high magnetic field of 12 tesla. This powerful field is created by running a very high electric current through coils of superconducting wire, which conduct electricity without resistance when cooled to almost absolute zero. Fermilab is the lead U.S. laboratory for this project and is fabricating half of the coils and conducting the final assembly and testing of 11 full cryoassembly magnet structures before shipping them to CERN. The U.S. in total is delivering half of the quadrupole magnets for the upgrade, while CERN is completing the other half.
“These are the next generation of superconducting magnets for accelerators,” said Fermilab’s Ruben Carcagno, the deputy project manager for the HL-LHC AUP. “This is the first time that this new technology will be deployed in a working machine. So it’s a big step.”
Fermilab is developing and constructing cavities like this one for the future HL-LHC. The cavity proper is the structure situated between the four rods. Photo: Leonardo Ristori
In addition to the magnets, the United States will deliver half of the crab cavities to CERN for the HL-LHC, while CERN completes the remaining cavities. The cavities to be produced in the United States are of a radio-frequency dipole (RFD) design and are the product of more than 10 years of research through LARP by Old Dominion University and SLAC National Accelerator Laboratory, with contributions from Thomas Jefferson National Accelerator Facility and U.S. industry. Fermilab will be responsible for fabricating and testing the RFD cavities before delivering them to CERN. These novel cavities will kick or tilt the beams just before they pass through each other to maximize the beam overlap and therefore the possibility of proton collisions.
Once it’s up and running, the HL-LHC will produce up to 15 million Higgs bosons per year, compared to the 4 million produced during the LHC’s 2015-2017 run. The higher luminosity will mean big changes for the LHC experiments as well, and the ATLAS and CMS detectors are undergoing major upgrades of their own. Learn more about Fermilab’s contributions to the HL-LHC upgrades to the CMS detector.
This image shows a three-track neutrino event in the MicroBooNE data with a muon, charged pion and proton candidate in the final state. Image: MicroBooNE collaboration
Physicists on the MicroBooNE collaboration at the Department of Energy’s Fermilab have produced their first collection of science results. Roxanne Guenette of Harvard University presented the results on behalf of the collaboration at the international Neutrino 2018 conference in Germany. The measurements are of three independent quantities that describe neutrino interactions with argon atoms, which make up the 170 tons of total target material used for neutrino collisions inside the MicroBooNE detector.
MicroBooNE started operations in the fall of 2015. The detector, about the size of a school bus, has recorded hundreds of thousands of neutrino-argon collisions since then. It features a time projection chamber with three wire planes that record the particle tracks created by those collisions, similar to a digital camera recording images of fireworks. The Booster particle accelerator at Fermilab is used to create the muon neutrino beam for the experiment.
It is the first low-energy neutrino experiment to make detailed observations of the subatomic processes that happen when a muon neutrino hits and interacts with an argon atom, leading to showers of secondary particles including protons, pions, muons and more. Using noise-reducing analysis techniques, MicroBooNE scientists can interpret the precise images of the particle tracks.
One of the new results reported at the Neutrino 2018 conference was the first measurement of the multiplicity – or number of particles – that these neutrino-argon collisions generate. A new paper describing these results was submitted to the journal Physical Review D last week. Other measurements determined the likelihood, or more precisely the cross section, of a neutrino-argon collision occurring and producing a neutral pion or a more inclusive final state.
The new results are of great importance for the groundbreaking measurements to be performed by neutrino experiments with liquid-argon TPCs. This includes the search for a fourth type of neutrino with the Short-Baseline Neutrino program at Fermilab, which comprises three neutrino detectors: the ICARUS detector, built by Italy’s INFN, refurbished at CERN, and then shipped to Fermilab in 2017; the new Short Baseline Near Detector; and MicroBooNE. The measurements are also important for the international Deep Underground Neutrino Experiment hosted by Fermilab, which will use both neutrino and antineutrino collisions with argon to search for differences between neutrino and antineutrino interactions, with the goal of understanding what role neutrinos played in the evolution of the universe.
“We are building on the success of neutrino interaction measurements in ICARUS and ArgoNeuT now with much larger statistics in MicroBooNE, to enable precise cross section measurements on argon,” said MicroBooNE co-spokesperson Bonnie Fleming, who holds a joint appointment with Fermilab and Yale University. “These are the first high-statistics, precision measurements on argon. They will be critical for the DUNE program.”
Nearly 200 scientists from 31 institutions in Israel, Switzerland, Turkey, the United Kingdom and the United States are members of the MicroBooNE collaboration. The experiment is funded by the U.S. Department of Energy Office of Science.