What is the purpose of electron multiplier?
An electron multiplier is used to detect the presence of ion signals emerg- ing from the mass analyzer of a mass spectrometer. It is essentially the “eyes” of the instrument (Figure 1). The task of the electron multiplier is to detect every ion of the selected mass passed by the mass filter.
Which are the MS detectors?
Ion Detectors
- Faraday Cup detector (or Cylinder electrode) The Faraday cup or cylinder electrode detector is very simple.
- Electron Multiplier.
- Photomultiplier (or Scintillation Counter)
Can electrons be multiplied?
When the average number of secondary electrons emitted from each dynode, which depends on the potential difference between dynodes, is more than one, electron multiplication occurs in the electron multiplier.
How do Dynodes work?
In a PMT, dynodes are electrodes in a vacuum tube that serve as an electron multiplier through SEE (see Figure 1). The dynodes are so arranged that the electric fields between them cause the electrons emitted by each dynode to strike the next with an energy of a few hundred eV.
How does a photocathode work?
A photocathode is a negatively charged electrode in a light detection device such as the input screen in an image intensifier (II) that is coated with a photosensitive compound. When this is struck by light photons, the absorbed energy causes electron emission due to the photoelectric (PE) effect.
What are the different types of mass spectroscopy?
There are six general types of mass analyzers that can be used for the separation of ions in a mass spectrometry.
- Quadrupole Mass Analyzer.
- Time of Flight Mass Analyzer.
- Magnetic Sector Mass Analyzer.
- Electrostatic Sector Mass Analyzer.
- Quadrupole Ion Trap Mass Analyzers.
- Ion Cyclotron Resonance.
What is an electron multiplier?
The discrete type of electron multiplier has a series of dynodes (metal plates that look like partially open venetian blinds) that are connected by a resistor chain so that the first dynode has a higher negative potential than the last dynode.
How many dynodes does the electron multiplier use?
The electron multiplier can use any number of dynodes in total, which use a coefficient, σ, and created a gain of σ n where n is the number of emitters.
What is the fundamental principle of the multiplier?
The fundamental principle of the multiplier is, as the name suggests, a multiplication of the number of electrons emerging from an electrode as compared with the number incident upon it. Electrodes, called dynodes, are so arranged that each succeeding generation of electrons is attracted to the next dynode.
How do you make a glass multiplier?
This type of multiplier is made by extruding lead-silicate glass. The multiplication principle is similar to the discrete-dynode type, but electrons are emitted from the continuous inner surface of the horn, instead of from a discrete metal dynode.