Measurement of the parameters affecting the time resolution of gallium arsenide detectors

The parameters governing the time resolution of a gallium arsenide strip telescope have been studied in various experimental conditions. The GaAs strip detectors are connected with a classical readout chain made of preamplifier, amplifier, constant-fraction discriminator and time-to-digital converter. The electronic noise, the amplitude and the fall time of the amplifier output pulse have been measured from /-55°C to /20°C. The mean value of the fall time is 950ps at /-55°C and has a linear dependence on the temperature. The time resolution of the gallium arsenide telescope is 173ps at /20°C. A silicon strip telescope processed by the same readout chain exhibits a time resolution of 213ps.