With silicon charged-particle detectors the timing signal is normally accessible at the output of the charge-sensitive preamplifier. Because the signal is fast and small, a fast amplifier must be employed in front of the timing discriminator. The Preamplifier and Amplifier sections of this catalog should be consulted for the proper choice of amplification. It is important to select a low-noise, charge-sensitive preamplifier with minimum rise time, followed by a fast amplifier with a similar rise time.

The timing jitter with this type of detector is dominated by the noise and slope contributions described in Equation (10). Consequently, the best timing resolution can be obtained with a constant-fraction discriminator, whose fraction and delay are selected for triggering at the point of maximum slope on the leading edge of the pulse. Use of the constant-fraction discriminator will also minimize the walk over a large dynamic range of pulse amplitudes. For practical examples of performance, see the data sheets for the Models 142A/B/C and 142AH.

Data for timing with surface barrier detectors are shown in Figs. 5–7. This information was obtained with a laser diode pulser and standard ORTEC electronics as shown in Fig. 5. Figures 6 and 7 show a typical timing resolution versus detector capacitance for this system.

Figure 5.  Block Diagram for Timing System Using Surface-Barrier Detectors.

Figure 6.  Typical Timing Resolution vs. Detector Capacitance.

Figure 7.  Typical Timing Spectrum for Surface-Barrier Detector System.