Ion Separation in a Magnetic Field

Ions accelerated from a source by a tension V acquire a kinetic energy given by  

In order for an ion to go through the magnetic sector, the two forces must balance each other, conditioned by the equality  

The relation (4.9) establishes that the radius rg of the trajectory within the magnet of an ion of a given m/z ratio depends on B and V. For given B and V values, ions of different m/z ratios will have circular trajectories of different radii. An ion collector composed of a very thin slot is placed at the exit of the magnetic sector. Only the ions exiting within the axis of the slot are detected. By scanning the value of B (most frequent case) or that of V, one detects in turn ions of different m/z ratios. 

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