A particular type of detector does not necessarily make only one sort of measurement. For example, a segmented calorimeter can be used to determine particle tracks; however, the primary aim of such a detector is to measure the energy. The main aim of drift chambers is a measurement of particle trajectories but these devices are often used for particle identification by ionisation measurements. There is a number of such examples.

This chapter considers the main physical principles used for particle detection as well as the main types of counters (detector elements). The detectors intended for the measurement of certain particle characteristics are described in the next chapters. A brief introduction to different types of detectors can be found in [1].

Ionisation counters

Ionisation counters without amplification

An ionisation counter is a gaseous detector which measures the amount of ionisation produced by a charged particle passing through the gas volume. Neutral particles can also be detected by this device via secondary charged particles resulting from the interaction of the primary ones with electrons or nuclei. Charged particles are measured by separating the charge-carrier pairs produced by their ionisation in an electric field and guiding the ionisation products to the anode or cathode, respectively, where corresponding signals can be recorded.