photomultiplier tubes
PMT
PMTs convert light into electrons and then amplify the electron signal. Classic photomultiplier tubes (PMT) work in the ultraviolet, visible, and near-infrared range of the electromagnetic spectrum. These are electron tubes that pick up weak light signals (up to individual photons) and amplify them to such an extent that free electrons produce more free electrons of lower energy, whereby the weak input signals are converted into measurable currents. They typically consist of a photocathode and a downstream secondary electron multiplier (SEM) in an evacuated glass bulb. PMTs can have dead times of tens of ns. A further development of the PMT, the hybrid photodetector, combines this with avalanche photodiodes.
PMTs are used in scintillation counters, fluorescence spectroscopy, astronomy, medical imaging, and other applications. They are ideal for detecting photons with high time resolution. As a rule, several high-voltage points (typically 500–1500 V) are required at the dynodes for operation.