A scintillator is a device or substance that absorbs high energy (ionizing) electromagnetic or charged particle radiation then, in response, fluoresces photons at a characteristic Stokes-shifted (longer) wavelength, releasing the previously absorbed energy. See also scintillation. Scintillators are defined by their short fluorescence decay times and optical transparency at wavelengths of their own specific emission energy, characteristics which set them apart from phosphors. The lower the decay time of a scintillator, that is, the shorter the duration of its flashes of fluorescence are, the less so-called "dead time" the detector will have and the more ionizing events per unit of time it will be able to detect. Klystrons give off both ionizing and electromagnetic radiation. ... Particle radiation is the radiation of energy by means of small fast-moving particles that have energy and mass. ... Fluorescence induced by exposure to ultraviolet light in vials containing various sized cadmium selenide (CdSe) quantum dots. ... Stokes shift is the difference (in wavelength or frequency units) between positions of the band maxima of the absorption and luminescence spectra of the same electronic transition. ... Scintillation is a flash of light produced in a transparent material by an ionizing event. ... A phosphor is a substance that can exhibit the phenomenon of fluorescence (glowing during absorption of radiation of another kind) or phosphorescence (sustained glowing without further stimulus). ...

Examples include

• thallium doped sodium iodide crystals in gamma cameras used for nuclear medicine radioisotope imaging.
• bismuth germanate (BGO) coincidence detectors for detecting back-to-back gamma rays emitted upon positron annihilation in positron emission tomography machines.
• the yellowish-white cerium-doped yttrium aluminum garnet (Ce:YAG) coating on the chip in some "white" light-emitting diodes (LEDs) is used as a phosphor but is also suitable for use as a scintillator when in pure single crystal form. This converts part of the visible blue light emitted by the LED chip to visible yellow light. The blue and yellow light together create the subjective impression of white light.

Scintillators are used in many physics research applications to detect electromagnetic waves or particles. There, a scintillator converts their wavelength [or kinetic energy] to light of a wavelength which can be detected by inexpensive or easy to handle detectors such as photomultiplier tubes. A gamma camera is an imaging device, most commonly used as a medical imaging device nuclear medicine. ... Nuclear medicine is a branch of medicine and medical imaging that uses unsealed radioactive substances in diagnosis and therapy. ... Positron emission tomography (PET) is a nuclear medicine medical imaging technique which produces a three dimensional image or map of functional processes in the body. ... Red, pure green, and blue LEDs. ...

In principle, scintillators can have any aggregate state: gaseous, liquid or solid state. Most scintillators for common use will come in solid state form with the commonest detectors being made of thallium-doped sodium iodide crystals; their popularity owing to a high impinging radiation to output light conversion efficiency. However, organic liquid scintillating fluids are well-suited for detecting very low energy particle radiation such as beta radiation from tritium by simply immersing the sample to be tested in the scintillation fluid, thereby negating detector absorption problems due to the very short mean free paths associated with low energy particles. General Name, Symbol, Number thallium, Tl, 81 Chemical series poor metals Group, Period, Block 13, 6, p Appearance silvery white Atomic mass 204. ... In semiconductor production, doping refers to the process of intentionally introducing impurities into an intrinsic semiconductor in order to change its electrical properties. ... Sodium iodide (NaI) is used in polymerase chain reactions (PCR) Categories: Chemistry stubs ... Tritium (symbol T or 3H) is a radioactive isotope of hydrogen. ...