Secondary emission
In physics, secondary emission is a term used to describe the emission of particles or radiation from surfaces or bodies, which is caused by "primary" particles or radiation. Primary particles are mostly fast electrons or ions ; primary radiation is high - energy X-ray or gamma radiation . The secondary particles are called secondary electrons or secondary ions, depending on their type.
Applications
The energy distribution and emission rate of the secondary electrons allow conclusions to be drawn about the surface properties and the material properties. This is used in secondary electron microscopy , the standard operating mode in the scanning electron microscope . The sample is bombarded with an electron beam and the secondary electrons that are released are detected.
In the secondary ion mass spectrometer , the generation of secondary ions by primary ions is used for surface analysis.
A secondary electron multiplier uses the generation of secondary electrons to amplify very small currents and thus make them easier to detect. The best-known application of such a multiplier is the photomultiplier .
Secondary electron emission as a disruptive effect
If the current strength of the electron or ion beam hitting a target is to be measured electrically, the escaping secondary electrons represent an additional, falsifying current component. In accelerator experiments, this is prevented by the secondary electrons - which have low kinetic energies - being generated by an electrical or magnetic auxiliary field the target can be deflected back.
literature
- Andrew Zangwill: Physics at Surfaces , Cambridge University Press 1988, ISBN 0-521-34752-1