Magnetics Business & Technology - July/August 2024 - 12

FEATURE ARTICLE
First U.S.-Built Focusing Magnet for LHC Upgrade Arrives at CERN, Uses New Superconducting
Material
nets is a tangible testament to the success
of the US Accelerator Upgrade Project, " said
Mike Lamont, CERN Director for Accelerators
& Technology. " This event not only marks a
crucial milestone in our collaboration with our
US partners, but also celebrates the outstanding
contributions shaping the future landscape
of particle physics at CERN. "
CERN celebrates the arrival of the first U.S.-built HL-LHC magnet. Nine
more will follow over the next two years to the Large Hadron Collider
in Switzerland.
After twenty years of research, development, testing and production,
the United States is now shipping state-of-the-art superconducting
accelerator magnets to CERN for the high-luminosity
upgrade to the Large Hadron Collider in Switzerland. At the heart of
these powerful magnets is a new superconducting material used for
the first time in a particle accelerator. Earlier, prototypes performed
successfully but exhibited shortcomings, however, the dedicated
teams of scientists and engineers overcame them with some design
and production adjustments.
Teams at the Department of Energy's Lawrence
Berkeley National Laboratory (Berkeley
Lab) play a key role in building the new magnets.
This summer, experts in the Accelerator
Technology & Applied Physics (ATAP) DiviMike
Lamont, CERN
director for accelerators
& technology
sion
and Engineering Division finished a project to turn superconducting
wire into the cables used to make the magnet coils. That's
no easy feat, since each cable is made in one continuous piece
made by wrapping 40 individual strands of wire around a stainlesssteel
core. If even one wire crossed over another anywhere along
the entire length - typically 470 meters - the cable would be ruined.
Once the cables were transformed into magnet coils at Fermilab
and Brookhaven Lab, they returned to Berkeley Lab, where technicians
assembled four coils into magnets called quadrupoles.
" These magnets are incredibly challenging to make, so completing
the first one and getting it safely to CERN is a huge milestone, "
said Soren Prestemon, who leads Berkeley Lab's contribution to the
LHC Accelerator Upgrade Project. " Now we're focused on finishing
the assembly of the remaining magnets, and excited about the
discoveries they'll make possible. "
The Large Hadron Collider smashes protons and other atomic
nuclei together at close to the speed of light, recreating conditions
that existed shortly after the Big Bang. Scientists study these collisions
to learn about subatomic particles and the fundamental laws
of physics. They look for answers to some of the biggest questions
in physics. What is the nature of dark matter? What happened to
all the antimatter? How did particles acquire mass during the early
universe?
The cryo-assembly containing two MQXFA magnets arrived at CERN in
November after a month in transit over land and sea.
On Dec. 18, the physics laboratory CERN in Geneva, Switzerland,
celebrated the arrival of a very large parcel from the United States.
Inside was a 13-meter-long assembly comprising two magnets with
4.2-meter-long coils. These are the first U.S.-built magnets for the
high-luminosity upgrade to the Large Hadron Collider, or HL-LHC.
Over the next few years, another nine assemblies will follow, thus
completing a two-decades' effort by a consortium of U.S. Department
of Energy national laboratories - Fermilab, Brookhaven, and
Berkeley Lab - to design and build new accelerator focusing magnets.
These magnets, along with those from CERN, will be installed
around two of the LHC's collision points in two years' time.
" In the realm of large scientific endeavors like the HL-LHC, global
collaboration and expertise play pivotal roles. The delivery of the
first cryo-assembly housing fully validated niobium-tin series mag12
Magnetics Business & Technology * July/August 2024
The magnets built by the U.S. High-Luminosity Accelerator Upgrade
Project will tightly squeeze the two proton beams traveling in opposite
directions around the LHC just before they collide. This tight
squeeze will contribute to increasing the LHC's collision rate by a
factor of 5 over the original design value. Together with other upgrades,
it will allow scientists to collect more data much faster than
ever before. With these huge data sets, scientists will be able to
study extremely rare subatomic events with high precision and explore
phenomena beyond what the current LHC capabilities allow.
Upgrading the collision rate is difficult. Scientists needed to create
magnets that are strong enough to focus and squeeze the proton
beams of the LHC into much tighter bunches as they collide head
on. So how are they doing it?
The answer is a rarely used and fussy superconducting material
called niobium-3-tin, or Nb3Sn. When cooled with liquid helium to
minus 271.25 degrees Celsius, Nb3Sn is an excellent superconductor
and transports electricity without resistance. It is a type of superconductor
that can reach higher magnetic fields than the standard
niobium-titanium currently used in LHC superconducting magnets.
The new magnets produce a maximum magnetic field of 12 tesla,
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Magnetics Business & Technology - July/August 2024

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