Berkeley Lab

HL-LHC AUP Receives CD-3 Approval

—ATAP, Engineering play key roles in multi-lab magnet program

Based on a story by Leah Hesla of Fermilab


A fully assembled quadrupole magnet

The U.S. Department of Energy has formally approved the High-Luminosity Large Hadron Collider Accelerator Upgrade Project (AUP) to go into series production mode, building and delivering components. Those components prominently include cutting-edge magnets designed and built with the help of ATAP and the Engineering Division.

The approval, known as Critical Decision 3, or CD-3, in DOE’s project-management process, is a milestone in the U.S. contributions to the high-luminosity upgrade of the Large Hadron Collider, or HL-LHC, at the European laboratory CERN. The approval follows a Fermilab Director’s Review in July 2020 and a DOE Review in November 2020.

This video highlights magnet-making efforts to support the High-Luminosity Large Hadron Collider upgrade at CERN in Europe. Three U.S. Department of Energy national labs — Berkeley Lab, Fermilab, and Brookhaven — are building superconducting magnets that can produce far stronger magnet fields than the magnets now in place at the LHC. This will enable more particle collisions and data to help us learn more about exotic particles and their properties. (Marilyn Sargent/Berkeley Lab)

Fermilab is lead lab in the AUP, in which the U.S. collaborators will contribute 16 magnets to dramatically focus the LHC’s near-light-speed particle beams to a tiny volume before colliding. In an aspect that does not involve Berkeley Lab, the AUP is also contributing eight superconducting radiofrequency cavities.

Berkeley Lab’s contributions, through our Superconducting Magnet Program/Berkeley Center for Magnet Technology (SMP/BCMT), include superconducting cables; insulation of the cables; and magnets (sidebar).

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With CD-3 approval, AUP collaborators can now move full speed ahead on building and delivering crucial components. Fermilab, Brookhaven National Laboratory and Berkeley Lab are currently building the magnet components and plan to begin delivering the first magnet cryoassembly by late 2021 for critical tests. Components will be installed in the HL-LHC from 2025 to early 2027.

“Gaining DOE’s endorsement to move to full production is a huge achievement. Knowing what it means for the future of particle physics — for the new physics that the HL-LHC will reveal and for future accelerators enabled by these technologies — makes it even more gratifying,” said Giorgio Apollinari, Fermilab scientist and HL-LHC AUP project manager. “I congratulate the entire AUP team on the milestone. They have been instrumental in ensuring the development and technical successes of the leading-edge technologies needed for the HL-LHC.”

Magnets By the Numbers

Berkeley Lab’s contributions to the AUP include 104 cables made of superconducting wire to be used in the magnets; the insulation of the cables; and the assembly of 26 four-meter-long quadrupole magnets, designated MQXFA, that will focus the LHC’s particle beams.

The total of 26 magnets includes 16 series-production magnets (the effort set in motion by CD-3 approval), plus a prototype, five pre-series production units, and four that may require reassembly. A net total of 20 magnets will be provided to CERN.

Two of the 20 magnets will go into each of the 10 magnet cryoassemblies — cooling and housing units that enable the magnets’ superconductivity — to be provided by the AUP. Eight of these 10 magnet cryoassemblies will be installed during the upgrade; the other two will serve as spares.

The AUP magnet cryoassemblies are designated Q1 and Q3. Between them will be the CERN-provided Q2 (in two segments, a and b). Together, Q1, Q2a/b, and Q3 are called an “inner triplet” of quadrupole magnets.

There will be an inner triplet on either side of each of the two major detectors, ATLAS and CMS, to focus the proton beams as they come from opposite directions en route to head-on collisions.

Multi-institutional teamwork in the time of COVID

The AUP is supported by the DOE Office of Science. The AUP team consists of six U.S. laboratories and two universities: Fermilab, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory, and Thomas Jefferson National Accelerator Facility (all DOE national laboratories), along with the National High Magnetic Field Laboratory, Old Dominion University, and the University of Florida. Each brings unique strengths to the challenges of designing and building these advanced magnets.

SMP/BCMT head Soren Prestemon said, “These are very challenging magnets that took excellence in multiple skill sets and a variety of facilities. From conductor through cabling, design and assembly of magnets, and testing, this has been teamwork at its best.”

“As the review committees have noted, the AUP has been notable not only for technical achievement, but also for managerial coordination,” added Interim ATAP Division Director Thomas Schenkel. “A coast-to-coast project for a customer several time zones away is never easy, and especially during the pandemic, when we can’t meet in person, they’ve done a remarkable job of coordinating their efforts.”

The AUP magnets use conductors made of niobium-tin to generate a stronger magnetic field compared to predecessor technology. This type of magnet will make its debut in the HL-LHC: its run will be the first time that niobium-tin magnets will be used in a particle accelerator for particle physics research.

To date, the team at Berkeley has assembled four of the 5 pre-series magnets, and is now gearing up for series production now that the CD-3 approval has been given. “These magnets are a culmination of more than 15 years of technology development starting with the LARP (LHC Accelerator Research Program) collaboration,” recounts Dan Cheng, who is the Deputy Level-3 Control Account Manager for the Magnet Structures task at LBNL. “That effort was the foundation of what all of our teams have achieved so far, but there are still many challenges ahead of us.”

“It is very exciting to see this cutting-edge magnet technology, which is enabling breakthrough science at the LHC, enter the production phase after the successful test of our first magnet and with the approval of CD-3,” said Kathleen Amm, the Brookhaven representative for the Accelerator Upgrade Project and director of Brookhaven’s Magnet Division. “The incredible talent across our national laboratories working seamlessly has made this possible.”

The LHC AUP magnets and cavities will be positioned near two of the LHC’s collision points — the ones that host the ATLAS and CMS particle detectors. These giant, stories-high underground instruments are also being upgraded to take full advantage of the HL-LHC’s higher rate of collisions.

Over the course of the project the AUP team has seen one success after another, hitting both technological and project milestones according to the schedule established in 2015, says Apollinari. The U.S. collaboration’s first focusing magnet, completed last year in a prototyping phase, met or exceeded specifications.

“Building such an ambitious machine requires not only vision but discipline in carrying it out — tight, transparent, respectful coordination with partners, including with funding agencies and the independent reviewers,” Apollinari said. “The achievement is not only that we received CD-3 approval, but how we got here. We met our goals on a timescale that was put down on paper five years ago. That’s thanks to incredible teamwork of everyone involved.”

Stronger magnets mean more-precise (and possibly new) physics

At the LHC, beams of protons race in opposite directions around the collider’s 17-mile circumference, colliding at high energies at four specific interaction points along the way. Scientists study the collisions to better understand nature’s constituent components and to look for exotic matter, such as dark matter.

The HL-LHC is expected to start operations in 2027 and run through the 2030s. The higher luminosity will enable a tenfold increase in the number of particle collisions, compared to the current LHC. This improvement will enable physicists to study particles such as the Higgs boson in greater detail. The increase in the number of collisions could also uncover rare physics phenomena or signs of new physics.

“HL-LHC is a truly global scientific undertaking that will usher in a new era of research and discovery in particle physics. AUP plays a critical role in making this possible,” said Fermilab Director Nigel Lockyer. “The technologies developed by AUP will be important not only for the operation of HL-LHC, but also for the viability of future hadron colliders and the future of the field of particles — beyond the end of the HL-LHC’s run.”