Signal Processing for Radiation Detectors

9Introduction to Digital Signals and Systems

The rapid developments of fast analog‐to‐digital converters (ADCs) and digital signal processing (DSP) systems have led to important progresses in nuclear instrumentation. This chapter is devoted to introduce some basic concepts of digital signals, analog‐to‐digital conversion, and DSP methodologies. A reader interested in a more detailed treatment of the subject can refer to the references cited in the text. These concepts will be used in the next chapter when we discuss the digital methods proposed for energy measurement, pulse timing, and pulse‐shape discrimination of radiation detectors pulses.

9.1 Background

An analog signal is a kind of signal that is continuously variable during its duration. All radiation detector pulses start out with an analog pulse. DSP requires to digitize the signals that include sampling the analog signal at regular time intervals and representing each of the samples with a binary number. This process is called analog‐to‐digital conversion and is performed by a device called ADC or waveform digitizer. In digital radiation detection systems, the digitization is commonly performed on the preamplifier or photomultiplier output, and the ADC output is subsequently passed to a specialized digital processor to perform numerical or computational operations on the digitized signals. The digital processor can process the input signals in real time or offline. In real‐time or online processing, the signals are ...