THE DELPHI SILICON STRIP MICROVERTEX DETECTOR WITH DOUBLE-SIDED READOUT

The silicon strip microvertex detector of the DELPHI experiment at the CERN LEP collider has been recently upgraded from two coordinates (R phi only) to three coordinates reconstruction (R phi and z). The new M icrovertex detector consists of 125952 readout channels, and uses nove l techniques to obtain the third coordinate. These include the use of AC coupled double sided silicon detectors with strips orthogonal to ea ch other on opposite sides of the detector wafer. The routing of signa ls from the z strips to the end of the detector modules is done with a second metal layer on the detector surface, thus keeping the material in the sensitive area to a minimum. Pairs of wafers are daisy chained , with the wafers within each pair flipped with respect to each other in order to minimize the load capacitance on the readout amplifiers. T he design of the detector and its various components are described. Re sults on the performance of the new detector are presented, with speci al emphasis on alignment, intrinsic precision and impact parameter res olution. The new detector has been taking data since spring of 1994, p erforming up to design specifications.