Signal Processing for Radiation Detectors

6Timing Measurements

The measurement of short time intervals between nuclear events is of paramount importance in many fields of nuclear science and technology. Example applications are radionuclides metrology, positron emission tomography (PET), nuclear data measurements, and nuclear physics research. We start this chapter with a discussion of the basics of pulse timing followed by a detailed description of different components of pulse timing systems. Pulse timing procedures with scintillation, semiconductor, and gaseous detectors are also separately discussed.

6.1 Introduction

Since each detected nuclear event is represented with an output detector pulse, the measurement of time intervals between the events is equal to measuring the difference between the arrival times of pulses from the corresponding detectors. The time intervals range from a few picoseconds to as large as a few microseconds. In some applications, it is only sufficient to determine if the time spacing between the nuclear events lies in a preset time window, while in many applications the distribution of the time difference between the events is required. The former is called coincidence measurement, while the latter is called time spectroscopy. Some examples of time difference measurements between detector pulses are shown in Figure 6.1. In Figure 6.1a, uncorrelated particles strike on two detectors, and thus the time difference between the arrival times of any pair of pulses will have a random value. Then, ...