IEEE Spectrum - North American - March 2015 - 12

Tougher InTerconnecTIons
A team of about 280 technicians undertook the checking and reinforcing of more
than 10,000 interconnections that connect the Large Hadron Collider's superconducting wires. These cables, which have a
trapezoidal cross section, are overlapped
for several centimeters, pressed tightly
together, and held in place with a silverbased solder. At full operation, the splices
can carry a current of 13 kiloamperes, and
the slightest fault would cause the junction to heat and fail.

MaR 2015

nORTh aMERICan

Back where it Belongs: A muon chamber is
slotted into place in preparation for the restart of
the Large Hadron Collider.

kilometer of the 27-kilometer machine
in a flood of coolant-the system lost a
much larger quantity of helium than
was expected.
"In response to this incident, we
increased the number of safety valves
on our vacuum systems, so that we do
not get this avalanche of helium pressure
that caused the displacement of magnets," says Laurent Jean Tavian, leader
of the cryogenic group at CERN's technology department.

The revision of the connections has
now been completed, reports JeanPhilippe Tock, who leads the project.
All junctions have been tested at room
temperature. Those displaying anomalies were resoldered. All junctions have
also been equipped with copper shunts,
which can take over in case of failure, he
says. The system that keeps watch on the
new junctions has also been upgraded bIgger daTa
to provide better accuracy and resolu- "The data acquisition and storage systion. "We have many more measuring tem has been overdesigned from the
points," says Tock. For example, voltage beginning. We would have needed much
surges that occur over groups of connec- more data than anticipated to run into
tions, which normally have a resistance problems," says Niko Neufeld, who is
of less than 3 nano-ohms, will automati- responsible for the upgrade of highcally shut down the accelerator. "We have speed data acquisition for LHCb. (LHCb
not invented new technology; we have is short for the LHC Beauty Experiment,
applied existing technology to a very high which seeks to detect b [beauty] quarks
level of quality and quality assurance to and anti-b quarks; a difference in their
decay rates would explain the matteran unprecedented level," he says.
antimatter asymmetry in the universe.)
Nevertheless, he and his colleagues have
safer cooLIng
When an electrical interconnection been upgrading data systems by replacbetween two helium-cooled magnets ing obsolete hardware with more effifailed in 2008-knocking askew accelera- cient and compact modern systems. In
tor magnets and damaging about half a the past CERN has developed and pio-

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Claudia MarCelloni de oliveira

ning explains some upgrades.
In September 2008 during a
final commissioning phase-
and before the accelerator
reached its planned maximum energy of 14 teraelectron
volts-one of the more than
10,000 interconnections for
wires supplying power to the
superconducting magnets of
the LHC failed, causing an arc
that melted through a helium
line and damaged a severalhundred-meter stretch of the
system. After a year of repairs,
the LHC started up and eventually reached a reduced collision energy of 7 TeV.
The upgrade being finished
now is to reach 13 TeV. And
it was clear from the beginning that it
would require a complete overhaul of the
interconnections. So CERN management
decided to shut down the accelerator for
a two-year period, starting in early 2013.
This allowed the LHC engineering teams
to update and upgrade several other systems, including the data gathering and
storage technology and the cryogenics,
which keep the system's superconducting magnets at a crisp 1.9 kelvins. Also,
the Atlas detector-one of four enormous
machines in which the actual particle collisions take place-was equipped with an
extra layer of particle detectors, increasing its precision substantially.
-a lex a nder hellem a ns

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