fotomultipliatoriai

Fotomultipliatoriai, also known as photomultiplier tubes (PMTs), are highly sensitive detectors of light. They work by converting photons into an electrical signal. The process begins when incident photons strike a photocathode, which is a material designed to emit electrons when illuminated. These emitted electrons are then accelerated by an electric field towards a series of electrodes called dynodes. Each dynode is held at a progressively higher positive voltage. When an electron from the photocathode strikes the first dynode, it causes the emission of several secondary electrons. This process is repeated at each subsequent dynode, creating a cascade effect. By the time the electrons reach the final electrode, the anode, their number is amplified significantly, resulting in a measurable electrical current. This amplification factor can be very large, allowing PMTs to detect even single photons.

The sensitivity and fast response time of fotomultipliatoriai make them useful in a variety of scientific and industrial applications. They are commonly employed in fields such as particle physics, astrophysics, medical imaging (like PET scanners), and in instruments for detecting low-level light, such as in spectroscopy and scintillation counting. The spectral response of a PMT is determined by the material used for the photocathode, allowing for detection across a range of wavelengths from ultraviolet to near-infrared. While very effective, PMTs are also susceptible to magnetic fields and can be fragile.