scintillaatori

Scintillaatori, known in English as scintillators, are materials that emit light when exposed to ionizing radiation. The emitted light is usually in the visible or near-ultraviolet range and is detected by a photosensor to measure the energy and timing of the radiation. Scintillation occurs when radiation transfers energy to the material, producing excited states that release photons as they decay back to the ground state.

Common scintillator materials include inorganic crystals such as sodium iodide doped with thallium (NaI(Tl)), cesium iodide doped with thallium (CsI(Tl)), bismuth germanate (BGO), and lutetium-based compounds like Lu2SiO5:Ce (LSO/LYSO). Organic plastic scintillators are also widely used. Inorganic crystals tend to offer higher stopping power and light yield, while plastics provide fast timing and ease of fabrication. Some materials are hygroscopic (notably NaI) and require hermetic sealing to prevent degradation.

Scintillators are typically read out with photodetectors such as photomultiplier tubes (PMTs) or solid-state devices like silicon photomultipliers (SiPMs) and photodiodes. The choice of photodetector, along with the scintillator’s emission spectrum, affects energy resolution, timing, and overall detection efficiency. Decay times can range from a few nanoseconds to hundreds of nanoseconds, influencing pulse shape and count-rate capability.

Applications span medical imaging (notably positron emission tomography, PET, and single-photon emission computed tomography, SPECT), nuclear and particle physics experiments, homeland security, and industrial radiography. In PET, fast inorganic crystals enable precise timing; NaI(Tl) has long been a workhorse for gamma spectroscopy. Performance depends on light yield, decay time, density, effective atomic number, and emission wavelength. Limitations include hygroscopicity, temperature dependence, and potential radiation damage for some materials.