A silicon pad shower maximum detector for a Shashlik calorimeter

The new luminosity monitor of the DELPHI detector, STIC (Small angle Tile Calorimeter), was built using a Shashlik technique. This technique does not provide longitudinal sampling of the showers, which limits the measurement of the direction of the incident particles and the e - pi separation, For these reasons STIC was equipped with a Silicon Pad Shower Maximum Detector (SPSMD). In order to match the silicon detectors to the Shashlik read out by wavelength shifter (WLS) fibers, the silicon wafers had to be drilled with a precision better than 10 mu m without damaging the active area of the detectors. This paper describes the SPSMD with emphasis on the fabrication techniques and on the components used. Some preliminary results of the detector performance from data taken with a 45 GeV electron beam at CERN are presented.