The Development and Testing of a Silicon Trigger Detector with 400 Elements for the Helios (NA 34) Experiment

A 30 mm diameter, 300 μm thick silicon detector has been constructed for the basic trigger element in the NA34 (HELIOS) experiment at CERN. It contains 400 discrete active junction detectors ("pads") which are connected to 400 low-noise hybrid preamplifiers giving 500 - 700 rms electrons noise level. Results of tests in spatially well-defined particle beams will be presented which verify the efficiency of each pad and its effective charge collection area.