Channeltron
A Channeltron , sometimes called in English Chanel PhotoMultiplier ( CPM ) is a kind of Photomultiplicateur (PM). Compared to the photomultipliers with discrete dynodes, it is simpler to feed and more compact.
General operation
The operation of the CPM is similar to that of the Photomultiplicateur.
It converts a very low level of light into photoelectrons via a semi-transparent photocathode. It is deposited on the surface of the window of entry.
When the Photo-électron S cross the zone between cathode and the anode, they are guided and accelerated to enter the channel. This channel is curved so that the photoelectrons strike the walls so that they emit an identical electron (one can regard this channel as a continuous Dynode). This event repeats many times and thus one can obtain an amplification going until 108.
The material deposited on the walls of the channel increases this effect.
More in detail
It functions on the same principle of amplification per secondary emission of electrons.
When a photoelectron strikes the photocathode at the entry of the CPM, it tears off an electron by photoelectric Effet to him. This electron under the effect of the Electric field generated by the food, will be accelerated and will enter in collision with the walls of the CPM. The energy at the time of this collision is such as one or more identical electrons are generated. This phenomenon resembles the photoelectric effect but with electrons like incidental particles.
Each electron rebounds several times on the wall so that at the exit of the CPM one can have an amplification of energy of about 10 8 . It has on average a response time of 3 NS for a typical profit of 10 6 with a dark current of 60 Pa typically knowing that it varies according to the profit and the studied wavelengths.
The implementation
The food of Channeltron is different from the PM with discrete dynodes because even if the required tensions are always important, Channeltron only feeds in 2 points (+ and -).
Description:
It is necessary to apply to the photomultiplier a difference in polarization between the photocathode and the beginning of the channel of 100 V typically.
It is necessary also that there is a difference in tension between the photocathode and the anode ranging between 1000 and 3000 V.
(It is by varying this last tension that one varies amplification, plus the tension is important, plus amplification is).
External bond
http://www.olympusfluoview.com/java/channelpmt/index.html
http://www.burle.com/cgi-bin/byteserver.pl/pdf/ChannelBook.pdf
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