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The OPAL Central Vertex Detector |
The vertex chamber is a 1 m long, 0.47 m diameter cylindrical drift chamber which is segmented radially into an inner layer of 36 cells with axial wires and an outer layer of 36 small angle (4 degree) stereo cells.
The axial cells provide a precise measurement of the position (50 microns) in the r-phi plane. A coarse measurement of the z-coordinate can be made by measuring the time difference between the signals from the two ends of the anode wire. The combination of axial and stereo cell information provides a precise z measurement for charged particles close to the interaction region.
OPAL tracking detectors
The silicon microvertex detector
The jet chamber