A SILICON PAD SHOWER MAXIMUM DETECTOR FOR A SHASHLIK CALORIMETER

The new luminosity monitor of the DELPHI detector, STIC (Small angle T ile Calorimeter), was built using a Shashlik technique. This technique does not provide longitudinal sampling of the showers, which limits t he 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 detecto rs to the Shashlik read out by wavelength shifter (WLS) fibers, the si licon wafers had to be drilled with a precision better than 10 mu m wi thout damaging the active area of the detectors. This paper describes the SPSMD with emphasis on the fabrication techniques and on the compo nents used. Some preliminary results of the detector performance fr om data taken with a 45 GeV electron beam at CERN are presented.