Magnetics Business & Technology - May/June 2024 - 20

RESEARCH & DEVELOPMENT
Solving the Mystery of One, then Two, Dead Magnets at Fermilab
world, cannot be perfect, " Moros says. So, the US team put the
magnet to the side and started testing another one. Again, the
current ramped, and again, it suddenly dropped. They tried to
revive it, but the current refused to climb: A second magnet was
dead.
" The worst part is that this happened twice-on two magnets-
back-to-back, " Ambrosio says. " It felt like being on the Titanic
after it encountered the iceberg. "
Was it just two unlucky coincidences? Or was a weakness in the
magnets' design about to sink the entire LHC upgrade project?
Finding the culprit was vital: The future of the LHC research program
depended on it. In this article, we're going to give you a few
clues but to learn the whole story and to find out the ending, you
will need to visit Symmetry Magazine, an online publication of
Fermilab and SLAC National Laboratory about particle physics,
where the story is told.
During a routine test, two HL-LHC magnets unexpectedly flatlined.
Was it just a coincidence, or did they have a common foe?
Not exactly murder is involved but there is plenty of sleuthing
and baffling dead-ends in " The Magnet Detectives " , a true tale
of one, then two, dead magnets amidst some intricate physics
at the Fermi National Accelerator Laboratory in Batavia, Illinois.
Run by the U.S. Department of Energy, Fermilab is America's
particle physics and accelerator laboratory, tasked with bringing
the world together to solve the mysteries of matter, energy,
space and time.
The fascinating tale begins when the reading on the currentmeter
was gradually climbing. Until it wasn't. In fact, it suddenly
dropped. " Uh-oh, " Giorgio Ambrosio remembers thinking. " Houston,
we have a problem. "
Ambrosio is a scientist at the US Department of Energy's Fermi
National Accelerator Laboratory who oversees the assembly
of the US-built magnets for the high-luminosity upgrade to the
Large Hadron Collider. By doubling the number of protons inside
the LHC and improving the beam dynamics, the upgrade will
increase experimental datasets by a factor of 10. This will enable
physicists to study rare physical phenomena and learn more
about the origin of mass and matter in the universe.
The HL-LHC upgrade needs 150 new accelerator magnets. In
the US, the LHC Accelerator Upgrade Project is building new
focusing magnets, which will squeeze the beam just before collisions
and will be twice as powerful as their predecessors. But the
new focusing magnet that Ambrosio and his US colleagues were
testing had failed; the magnet was dead.
The 5-meter-long electromagnets need to carry 16,530 amperes
of current-roughly as much as a bolt of lightning. Because they
become superconductors when cooled to very low temperatures,
the magnets can carry this huge current without generating any
heat. Scientists like Ambrosio introduce and gradually increase
the current to test and " train " the magnets before use.
Ambrosio and colleagues like CERN fellow Alice Moros know
that " things not working " is part of the process of science-especially
when working with complex, one-of-a-kind, not commercially
available technology. " A magnet, like everything else in the
20 Magnetics Business & Technology * May/June 2024
Suspect Number 1 was the cable winding. Each magnetic coil
consists of a single cable, which is wrapped 50 times lengthwise
around a 4.2-meter-long titanium pole. The cable is delicate
because it consists of 40 twisted wires filled with brittle niobiumtin
filaments. If one of these wires fell out of place, it could create
a pinch point that would compromise the entire coil. In the broken
coil, " we had to fix a wire two times during the winding, " Ambrosio
says. " So we had the question, did the wire move again? "
Fermilab, focused on solving the mysteries of physics, encountered a
mystery of two dead magnets.
Suspect Number 2 was an unforeseen delay. After winding,
technicians transform the raw coil into a functional and sturdy superconducting
magnet through heat treatments, applying binding
agents, and soldering on components. The winding and curing
usually take a couple of weeks, but their victim happened to be
one they were working on when COVID first struck. " We started
the coil fabrication and then had to stop for 12 weeks, " Ambrosio
says. " This is pretty unusual... But did it have an impact? "
Suspect Number 3 was a broken symmetry. The focusing magwww.MagneticsMag.com
http://www.MagneticsMag.com
Magnetics Business & Technology - May/June 2024

Table of Contents for the Digital Edition of Magnetics Business & Technology - May/June 2024
