Fotomultiplierien

Fotomultiplierien, known in English as photomultiplier tubes (PMTs), are highly sensitive electronic devices used to detect and amplify low levels of light. They are commonly employed in scientific, medical, and industrial applications, including spectroscopy, medical imaging, nuclear and particle physics, and astrophysics.

A photomultiplier tube consists of a vacuum tube with a photocathode, a series of dynodes, and an anode. When incident photons strike the photocathode, they eject electrons via the photoelectric effect. These primary electrons are then accelerated towards the first dynode by an electric field. Upon striking the dynode, each electron releases multiple secondary electrons, resulting in an electron cascade. This multiplication process occurs across several dynodes, amplifying the initial signal exponentially. The resulting amplified electron pulse reaches the anode, producing a measurable electrical signal proportional to the incident light intensity.

Photomultiplier tubes are valued for their extremely high sensitivity, fast response time, and wide spectral range. They can detect single photons, making them ideal for applications that require precise light measurement at very low intensities. However, they are also sensitive to magnetic fields and have limitations in their operational voltage and size.

Advancements in photodetector technology have introduced alternatives such as avalanche photodiodes and silicon photomultipliers, but PMTs remain widely used due to their unparalleled sensitivity and dynamic range. Despite their age, photomultiplier tubes continue to play a vital role in scientific research where detecting faint light signals is critical.