by Playfuls Staff |
21st November 2006
The largest superconducting magnet ever built has
successfully been powered up to its operating conditions at the first attempt.
Called the Barrel Toroid because of its shape, this magnet is a vital part of
[more] ATLAS, one of the major particle detectors being prepared to take data
at CERN's Large Hadron Collider (LHC), the new particle accelerator scheduled
to turn on in November 2007. ATLAS will help scientists probe the big questions
of the Universe – what happened in the moments after the Big Bang? Why does the
material in the Universe behave the way it does? Why is the Universe we can see
made of matter rather than anti-matter? UK
scientists are a key part of the ATLAS collaboration and Dr Richard Nickerson,
UK ATLAS project leader, who is from the University of Oxford
welcomed this important milestone "The toroidal magnets are critical to
enabling us to measure the muons (a type of particle) produced in interactions.
These are vital to a lot of the physics we want to study, so the successful
test of the magnets is a great step forward."
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 will work together
with other magnets in ATLAS to bend the paths of charged particles produced in
collisions at the LHC, enabling important properties to be measured. Unlike
most particle detectors, the ATLAS detector does not need large quantities of
metal to contain the field because the field is contained within a doughnut
shape defined by the coils. This allows the ATLAS detector to be very large,
which in turn increases the precision of the measurements it can make.
At 46m long, 25m wide and 25m high, ATLAS is the largest
volume detector ever constructed for particle physics. Among the questions
ATLAS will focus on are why particles have mass, what the unknown 96% of the
Universe is made of, and why Nature prefers matter to antimatter. Some 1800
scientists from 165 universities and laboratories (including 12 from the UK)
representing 35 countries are building the ATLAS detector and preparing to take
data next year.
The ATLAS Barrel Toroid was first cooled down over a
six-week period in July-August to reach –269oC. It was then powered up
step-by-step to higher and higher currents, reaching 21 thousand amps for the
first time during the night of 9 November. This is 500 amps above the current
needed to produce the nominal magnetic field. Afterwards, the current was
switched off and the stored magnetic energy of 1.1 GJ, the equivalent of about
10 000 cars travelling at 70km/h, has now been safely dissipated, raising the
cold mass of the magnet to –218oC.
"We can now say that the ATLAS Barrel Toroid is ready
for physics," said Herman ten Kate, ATLAS magnet system project leader.
