Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. These detectors multiply the signal produced from the incident light from which single photons are detectable. Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region, but longer than that of soft X-rays. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ... In physics, the photon (from Greek φοτος, meaning light) is a quantum of excitation of the quantised electromagnetic field and is one of the elementary particles studied by quantum electrodynamics (QED) which is the oldest part of the Standard Model of particle physics. ...

Schematic of a photomultiplier tube coupled to a scintillator.

Photomultipliers are constructed from a glass vacuum tube which houses a dynode and an anode. Incident photons strike the photocathode material which is present as a thin deposit on the entry window of the device, with electrons being produced as a consequence of the photoelectric effect. These electrons are directed by the focusing electrode towards the electron multiplier, where electrons are multiplied by the process of secondary emission. Photomultiplier tube I, the creator of this image, hereby release it into the public domain. ... Photomultiplier tube I, the creator of this image, hereby release it into the public domain. ... In electronics, a vacuum tube (American English) or (thermionic) valve (British English) is a device generally used to amplify, or otherwise modify, a signal by controlling the movement of electrons in an evacuated space. ... One of a series of electrodes in a photomultiplier tube. ... Diagram of a zinc anode An anode (from the Greek άνοδος = going up) is the positive electrode in an electrolytic system or circuit. ... In physics, the photon (from Greek φοτος, meaning light) is a quantum of excitation of the quantised electromagnetic field and is one of the elementary particles studied by quantum electrodynamics (QED) which is the oldest part of the Standard Model of particle physics. ... In an electron tube, a negatively charged electrode coated with a photosensitive compound. ... Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ... The photoelectric effect is the emission of electrons from matter upon the absorption of electromagnetic radiation, such as visible light or ultraviolet radiation. ... An electrode is a conductor used to make contact with a nonmetallic part of a circuit (e. ... An electron multiplier (continuous dynode electron multiplier) multiplies charge. ...

The electron multiplier consists of a number of electrodes, called dynodes. Each dynode is held at a more positive voltage than the previous one. The electrons leave the photocathode, having the energy of the incoming photon. As they move towards the first dynode they are accelerated by the electric field and arrive with much greater energy. On striking the first dynode, more low energy electrons are emitted and these, in turn, are accelerated toward the second dynode. The geometry of the dynode chain is such that a cascade occurs with an ever-increasing number of electrons being produced at each stage. Finally the anode is reached where the accumulation of charge results in a sharp voltage pulse indicating the detection of a photon at the photocathode An electrode is a conductor used to make contact with a nonmetallic part of a circuit (e. ... Properties The electron is a fundamental subatomic particle which carries a negative electric charge. ...

Photomultiplier

Amplification can be as much as 10⁸ meaning that measurable pulses can be obtained from single photons. The combination of high gain, low noise, high frequency response and large area of collection have meant that these devices still find applications in particle physics, astronomy and medical imaging. Their replacement by semiconductor devices has long been predicted but has never been achieved. Download high resolution version (837x2124, 275 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (837x2124, 275 KB) Wikipedia does not have an article with this exact name. ... In physics, the photon (from Greek φοτος, meaning light) is a quantum of the electromagnetic field, for instance light. ... Particles erupt from the collision point of two relativistic (100 GeV) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... Astrometry: the study of the position of objects in the sky and their changes of position. ... Medical imaging is the process by which physicians evaluate an area of the subjects body that is not normally visible. ... Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium, and gallium arsenide. ...

See also

• Geiger counter

An antique Victoreen civil defense survey meter model CDV-717 with detachable remote sensing unit (a type of low accuracy geiger counter). ...

References

• Engstrom, Ralph W., Photomultiplier Handbook, RCA (1980).
• anon, Photomultiplier Tubes: Principles and Applications, Philips Photonics, Brive, France, (1994).
• anon, Photomultiplier Tubes: Basics and Applications (Second Edition), Hamamatsu Photonics, Hamamatsu City, Japan, (1999).
• Flyckt, S.O. and Marmonier, C., Photomultiplier Tubes: Principles and Applications, Photonis, Brive, France, (2003).

External links

Wikimedia Commons has media related to:

Photomultiplier

• Electron Multiplier Simulation of electron multiplier tube
• Molecular expressions A java simulation and tutorial on photomultiplier tubes
• Photomultiplier Tubes Basics and Applications from Hamamatsu Photonics
• Photomultiplier Handbook from Burle Industries, essentially the Engstrom-RCA Handbook reprinted
• Photomultiplier Tubes: Principles and Applications the Photonis applications book