Wiring a particle "trap"

7 October 1998

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Many modern experiments in particle physics record the tracks of charged particles as they pass though a detector called a drift chamber, which contains a volume of gas crossed by fine wires. High voltage on some wires sets up an electric field within the drift chamber. When a charged particle passes through and ionizes the gas, the electrons and resulting positive ions are made to drift in opposite directions by the electric field. The signals induced on the wires by the movement of the positive ions are recorded and a computer program can then reconstruct the tracks of the charged particles (see here). This week's image shows the computer-controlled wiring machine used to thread some 25,000 wires through the cylindrical Central Tracking Detector (CTD) - the main core of the ZEUS detector at the electron-proton collider HERA, at the DESY laboratory in Germany. The chamber itself, which is nearly 2.5 m long and 1.7 m in diameter, was built in the Physics Department at Oxford University.

Credit: Physics Photographic Unit, University of Oxford

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