Layer 3: Central Outer Tracker (COT)
Outside of the silicon detector, the central outer tracker works in much the manner as the silicon detector as it is also used to track the paths of charged particles and is also located within a magnetic field. The COT, however, is not made of silicon. Silicon is tremendously expensive and is not practical to purchase in extreme quantities. COT is a gas chamber filled with tens of thousands of gold wires arranged in layers and argon gas. Two types of wires are used in the COT: sense wires and field wires. Sense wires are thinner and attract the electrons that are released by the argon gas as it is ionized. The field wires are thicker than the sense wires and attract the positive ions formed from the release of electrons. There are 96 layers of wire and each wire is placed approximately 3.86mm apart from one another. As in the silicon detector, when a charged particle passes through the chamber it ionizes the gas. This signal is then carried to a nearby wire, which is then carried to the computers for read-out. The COT is approximately 3.1 m long and extends from r = 40 cm to r = 137 cm. Although the COT is not nearly as precise as the silicon detector, the COT has a hit position resolution of 140μm and a momentum resolution of 0.0015 (GeV/c)−1.
Read more about this topic: Collider Detector At Fermilab
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