sekundääriemissiosuhteen

Sekundääriemissiosuhde, often translated as secondary emission ratio, is a fundamental concept in vacuum electronics and plasma physics. It describes the phenomenon where incident electrons striking a surface cause the emission of secondary electrons from that surface. The sekundääriemissiosuhde, denoted by the Greek letter gamma (γ), is defined as the ratio of the number of secondary electrons emitted to the number of primary electrons incident on the surface.

The value of γ is highly dependent on several factors, including the material of the surface, the energy of the incident electrons, and the angle of incidence. Different materials have varying work functions and atomic structures, which influence how readily secondary electrons can be liberated. For most materials, γ is less than 1 at low primary electron energies, meaning more electrons leave than arrive. However, as the primary electron energy increases, γ can rise significantly, often exceeding 1. This means that for a given energy range, the impact of one primary electron can result in the emission of multiple secondary electrons.

Beyond a certain energy threshold, the secondary emission ratio typically begins to decrease again, eventually falling below 1. This behavior is crucial in the operation of various electronic devices. For instance, it plays a role in the functioning of vacuum tubes like photomultiplier tubes and klystrons, where it is exploited to amplify electron currents. Understanding and controlling the sekundääriemissiosuhde is vital for optimizing the performance and preventing unwanted effects like spurious discharges in these applications. It also has implications in areas such as electron microscopy and particle accelerators.