End-Cap Toroid
Two End-Cap Toroids are positioned inside the Barrel Toroid, one at each
end of the Central Solenoid. They provide the magnetic field in the
forward regions of the ATLAS detector across a radial span of 1.7 to
5 meters. The eight coils of each End-Cap Toroid are assembled as a single
unit inside one large cryostat.
The castellated cryostat vacuum vessel makes it possible to retract the
End-Cap Toroids from the operating position to allow access to the centre
of the detector.
The coils of the End-Cap Toroids are rotated by 22.5 degrees with respect
to the Barrel Toroid coils which allows a radial overlap and the
optimisation of the magnetic bending power in the interface region of the
toroids.
Each coil consists of two double pancakes wound directly in an aluminium
coil casing and is about 4 by 4.5 meters large with a weight of roughly
13 tonnes. One complete End-Cap Toroid has a diameter of 11 meters, a
width of 5 meters and a weight of almost 240 tonnes.
The End-Cap Toroids are electrically connected in series with the Barrel
Toroid and likewise operated at a current of 20,500 amperes providing a
peak field of 4 tesla.
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General