The world's largest superconducting magnet was successfully
brought online recently as part of CERN's Large Hadron
Collider (LHC), the new particle accelerator scheduled for
full scale use in November 2007. The magnet charged and operated
successfully on its first attempt. The magnet, called the
Barrel Toroid, provides the powerful magnetic field for ATLAS,
one of the major particle detectors for LHC.
The ATLAS Barrel Toroid consists of eight superconducting coils, each in the shape of a round-cornered rectangle 5m wide, 25m long and weighing 100 tonnes, all aligned to millimetre precision. It is designed to operate in concert with the other installed magnets to bend the paths of charged particles produced in collisions at the LHC.
|The experimental ATLAS detector began construction in 2004.|
© Nikolai Schwerg
A unique innovation behind the ATLAS detector is that it doesn't
require large amounts of metal to contain the magnetic field.
The field is contained within a doughnut shape defined by the
coils, allowing for the increased precision of its measurements.
ATLAS is the largest volume detector ever constructed for particle
physics, measuring 46m long, 25m wide and 25m high. It has been
designed to help researchers solve some of the most important
questions in physics: Why do particles have mass? What is the
unknown 96 percent of the Universe made of? and Why does Nature
prefer matter to antimatter? Some 1800 scientists from 165 universities
and laboratories representing 35 countries are building the
ATLAS detector and preparing for its use next year.
Superconductors operate under cryogenic conditions and to reach
the temperature of 269° C below zero, ATLAS was progressively
cooled over a six-week period. It was then slowly charged up
to 21 000 amps, 500 above the current needed to produce the
nominal magnetic field.
“We can now say that the ATLAS Barrel Toroid is ready
for physics,” said Herman ten Kate, ATLAS magnet system
The ATLAS Barrel Toroid is financed by the ATLAS Collaboration
and has been built through close collaboration between the French
CEA-DAPNIA laboratory (originator of the magnet's design),
Italy's INFN-LASA laboratory and CERN. Components have
been contributed by national funding agencies from France (CEA),
Italy, Germany (BMBF), Spain, Sweden, Switzerland, Russia, and
the Joint Institute for Nuclear Research (JINR), an international
organisation based near Moscow.