electron multiplier


Electron multipliers are used to detect electrons or other charged particles, for example in a quadrupole mass spectrometer. There operating principle is illustrated here using a so-called continuous dynode electron multiplier (a channeltron). This consists of a little glass tube which is coated with a highly resistive material in the inside. It is shown in the sketch below.


Between the front and the back of the channeltron a high voltage is applied, 2 keV or so, depending on the type of channeltron. When a charge particle now hits the entrance and the material inside, it can give rise to the re-emission of several electrons, which are accelerated in the electric field inside the channeltron. If the total voltage over the whole device is high enough, the electrons acquire sufficient kinetic energy to hit other electrons out when they hit the wall the next time. In this way an electron avalanche is created, generating 107 or so electrons at the exit for a single electron coming in. This current pulse can then be measured.


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