Barrel Toroid
The Barrel Toroid consists of eight flat race-track coils each of them
consisting of two double pancake windings housed in a common aluminium
casing 25 meters long and 5 meters wide. It generates the magnetic field
for the central region of the muon detector. The coils are grouped in a
torus shape maintained by a system of 16 supporting rings.
All connections are made through a cryogenic ring which combines the eight
coils.
Each coil is mounted in an individual cryostat and indirectly cooled
by liquid helium flowing in tubes attached to the coil casing.
A single coil has a weight of some 40 tonnes to which its cryostat adds
another 40 tonnes. The total Barrel Toroid assembly has an outer diameter
of 20 meters and approaches a weight of 830 tonnes. The toroid is operated
at a current of 20,500 amperes and reaches a peak field of 4 tesla.
After integration and test, the eight coils are transported to the ATLAS
cavern and assembled as a toroid. It is first then that the Barrel Toroid
will be operated as a complete system. Due to its exceptional size it was
not feasible to assemble and test the integrated Barrel Toroid before
underground installation. For the separate tests of the eight coils,
a magnetic mirror is used to induce the same level of forces as expected
in the full assembly.
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General