Photomultiplier Tube (PMT) is a vacuum electronic device used for detecting and amplifying light signals. Its main function is to convert weak light signals into electrical signals, with characteristics such as high gain, high sensitivity, low noise, fast response, and a wide wavelength response range. The following is a detailed explanation about photomultiplier tubes:



Working principle:
Photoelectric effect: When photons are incident on the surface of the photocathode of a photomultiplier tube, their energy is absorbed by the photocathode material, allowing electrons in the photocathode to gain sufficient energy and escape. This process is called photoelectron emission.
Electron doubling: Photoelectrons are emitted from the photocathode and enter the doubling system. The multiplication system is composed of a series of metals or composite materials, with each stage having an electrode and a shielding film that leads out electrons. Under the action of an electric field, photoelectrons collide with ions in the multiplication stage, producing more free electrons. These electrons are accelerated to collide with the shielding film of the next stage, producing new electrons. This process can be repeated multiple times, resulting in an exponential increase in the number of photoelectrons.
Collection and output: After being multiplied, photoelectrons finally enter the collection stage, which gathers them and converts them into a strong electrical signal. This electrical signal can be output through the output port for signal amplification, recording, or other applications.



Structural composition:
The photomultiplier tube mainly consists of a photocathode, a multiplication system (including a series of multiplication electrodes), and a collection electrode.
There are two types of amplification poles: aggregated and non aggregated. The aggregated type includes squirrel cage type, linear focusing type, etc., while the non aggregated type includes louver type, box grid type, etc. Different structural types have different characteristics and application scenarios.


Application field:
Photomultiplier tubes are widely used in scientific research, nuclear physics experiments, chemical analysis, medical imaging, and other fields. For example, in spectral analysis, it can measure extremely weak radiation power in the wavelength range of 200-1200 nanometers; In medical imaging, it is commonly used in equipment such as fluorescence microscopy and flow cytometry.
Photomultiplier tube is a powerful photoelectric converter device that can convert weak light signals into strong electrical signals, and has characteristics such as high sensitivity, low noise, and fast response. It has wide applications in multiple fields.