Sekundääriemissioiden

Sekundääriemissiot refer to the emission of electrons from a surface when it is struck by energetic particles, such as ions, electrons, or photons. This phenomenon is distinct from primary emission, which involves the direct release of electrons from a material due to heat (thermionic emission) or the photoelectric effect.

The process of secondary emission begins when an incident particle transfers its energy to the atoms within the target material. This energy can excite electrons in the material to higher energy levels. If these excited electrons have enough kinetic energy to overcome the work function of the material, they can escape from the surface, becoming secondary electrons. The number of secondary electrons emitted per incident particle is quantified by the secondary emission yield, often denoted by the Greek letter delta ($\delta$). This yield is dependent on factors such as the energy and type of the incident particle, the material properties of the target, and the angle of incidence.

Sekundääriemissiot play a crucial role in various technological applications. For instance, they are fundamental to the operation of vacuum tubes, photomultiplier tubes, and image intensifier tubes, where they are used to amplify weak signals. In cathode ray tubes (CRTs), secondary emission from the screen can affect image quality. Understanding and controlling secondary emission is also important in plasma physics and in the design of particle accelerators and fusion devices, where it can influence beam stability and wall interactions. The phenomenon is also observed in everyday objects like touchscreen devices.