Magnetic sector illustration

Fig. 4.15. A 90° magnetic sector illustrating m/z separation and direction focusing in a plane (angles are shown exaggerated). Reprinted from Ref. [1] with permission. American Association for the Advancement of Science, 1979.

Figure 4.4. Illustrating the operation of a magnetic sector mass analyser.

The dwelltime of ions within the ion source is defined by the extraction voltages applied to accelerate and focus them into an ion beam and by the dimensions of that ion source. In standard El ion sources the freshly formed ions dwell about 1 ps before they are forced to leave the ionization volume by action of the accelerating potential. [41] As the ions then travel at speeds of some 10 m s they pass the mass analyzer in the order of 10-50 ps (Fig. 2.9). [9] Even though this illustration has been adapted for a double focusing magnetic sector mass spectrometer, an ion of m/z 100, and an acceleration voltage of 8 kV, the effective time scales for other types of instruments (quadrupole, time-of-flight) are very similar under their typical conditions of operation (Table 2.4). 

Fig. 4.18. Direction focusing properties of a 180° magnetic sector on a diverging beam of ions of the same m/z and the same kinetic energy and effect on ions of different m/z- In this illustration, B has to come out of the plane towards the reader for positive ions.

Modem mass spectrometers are usually one of four types magnetic sector, quadrupole, time-of-flight, or ion trap. A brief introduction to each is provided. Classical applications are discussed to illustrate how these devices have shaped the landscape of elemental and isotopic chemical analysis. 

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