PhotomultiplierRöhren

PhotomultiplierRöhren, often abbreviated as PMTs, are highly sensitive detectors of light. They operate by converting incident photons into a measurable electrical signal. The process begins when photons strike a photocathode, a thin layer of material that readily emits electrons when illuminated. These emitted electrons are then accelerated and focused by an electric field towards a series of electrodes called dynodes. Each dynode is maintained at a progressively higher positive voltage. When an electron strikes a dynode, it causes the emission of several secondary electrons. This cascading effect is repeated at each subsequent dynode, resulting in a significant amplification of the initial electron signal. Finally, the amplified electron cloud is collected by an anode, producing a measurable current pulse. The number of secondary electrons emitted per incident electron is known as the secondary emission yield, and the overall amplification factor of a PMT can be very large, often in the range of 10^5 to 10^8. This high sensitivity makes PMTs suitable for detecting very faint light sources, such as single photons. Their applications are diverse, including spectroscopy, medical imaging, particle physics experiments, and astronomical observations.

---