Energy Resolution of a Detection System

The quality of the performance of a detection system used for energy measurements is characterized by the width of the pulse-height distribution obtained with particles of the same energy (monoenergetic source). Even in the case where each particle deposits exactly the same energy in the detector, the pulse-height distribution will not be a single line (like that shown in Fig. 9.9a) instead, it will have a certain finite width (Fig. 9.10) due to 

Statistical fluctuations in the number of charge carriers produced in the detector 

Electronic noise in detector itself, the preamplifier, and the amplifier 

The width, measured at half of the maximum of the bell-shaped curve, is indicated by F or by full width at half maximum (FWHM). The ability of a detector to identify particles of different energies, called the energy resolution, is given either in terms of F or in terms of the ratio R(Eq), where 

The width F is given in energy units, while the ratio RiEg) is given as a percentage. 

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