Photomultipliers (PMTs) are ideally suited in a number of photodetection measurements, provide a wide dynamic range and an excellent linearity, with a good speed of response and a very low excess noise. PMTs are available in a variety of formats, with an ample choice of spectral responses, ranging from ultraviolet (down to λ≈100 nm) to infrared (up to λ≈1700 nm with NEA photocathodes).

This chapter begins by presenting a short introduction to PMT operation followed by an analysis of the elements of the PMT — photocathode, electron optics, and multiplying chain and related parameters. A section is devoted to summarize the theoretical results of PMT response. Then, specifications and characteristics of PMTs are discussed. Finally, the most widespread applications of PMTs to measurements and the performance that can be obtained are reviewed.