The pulse digitization for measuring the time of flight of ionizing particles

A new method of processing the output signals of preamplifiers connected to silicon strip detectors operated for time-of-flight measurements is described. Pulse pairs coming out from the two arms of a silicon strip telescope are stored in a transient digitizer with a minimum sampling period of 5 ps and software analyzed. This method eliminates both discriminators and time-to-digital converters from the readout system. Using the new technique, the time resolution of the telescope, at various thresholds, is determined by software algorithms that reproduce the functions of both amplitude and constant-fraction discriminators. Measurements of time resolution of the telescope of the new readout system, using electrons from the source 90Sr are reported. At room temperature the time resolution of the telescope, obtained with this new technique and an unoptimized software algorithms is 235±55 ps to be compared with that of 160±35 ps resulting from the use of the classical readout method. Technical limitations of these measurements are discussed.