Scintillator

A scintillator is a substance that absorbs high energy (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.

Scintillators are used in many physics research applications to detect photomultiplier tubes (PMTs).

Types of Scintillators

Common scintillators used for radiation detection include inorganic crystals, organic plastics and liquids. However, many materials scintillate at some level; scintillation of liquid neon plays a role in some ultra-low-background experiments. Most scintillators for common use are either inorganic crystals or plastics, the most common being mean free paths associated with low energy particles.

Organic liquids

The organic crystal scintillator can be dissolved in a transparent liquid, for example in mineral oil, maintaining properties similar to the organic crystal, depending on purity and concentration.

For the specific use of this form of scintillator, see Liquid scintillation counting.

Organic crystals

These are organic molecules which have an aromatic ring; the anthracene.

Organic plastics

The organic crystals can be also be dissolved in a transparent plastic that becomes solid at ambient temperature, like fluorophor is added in amount of about 1 wt.%.

Plastic scintillators are robust and reliable, but also quirky. They undergo aging, gradually losing light yield with time, with solvents, high temperatures, radiation, or mechanical load accelerating the process. The surface can be damaged by formation of microcracks which cause light loss by reflection. Plastic scintillators are also sensitive to airborne oxygen which lowers their yield; this is known as atmospheric quenching. Some plastics change their yield slightly when subjected to magnetic fields. Radiation damage leads to formation of color centers (F-Centers) which absorb in ultraviolet and blue part of spectrum, lowering the optical yield. [1]

Some polymers can scintillate on their own. A commonly used polymer scintillator is polyvinyl toluene (PVT).

Inorganic crystals

Are usually composed of nanoseconds.

NaI(Tl) (doped sodium iodide) crystals
are used in nuclear medicine radioisotope imaging. NaI was the first known inorganic scintillator, discovered by Robert Hofstadter in the 1940's.
CsI(Tl) (thallium doped cesium iodide) crystals are an alternative to NaI(Tl). They are more mechanically durable and have better resistance to moisture.
BaF₂ (Barium fluoride)
BGO (bismuth germanate) has a higher stopping power, but lower yield than NaI(Tl)
It is often used in coincidence detectors for detecting back-to-back gamma rays emitted upon positron emission tomography machines.
Cerium-doped 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.
LaBr₃(Ce) (lanthanum bromide)
LuI₃ (lutetium iodide)
Gd₂O₂S (terbium-doped gadolinium oxysulfide, GOS)
CaWO₄ (calcium tungstate)
CdWO₄ (cadmium tungstate), used in fluoroscopes
PbWO₄ (lead tungstate)
ZnWO₄ (zinc tungstate)
Lu₂SiO₅ (lutetium oxyorthosilicate), also known as LSO, used in positron emission tomography