The scintillation emission of a typical plastic scintillator has a maximum of around 425 nm. Plastic scintillators are characterized by a relatively large light output — typically 25-30% of NaI(Tl) — and a short decay time of around 2 ns. This makes the material suited for fast timing measurements.
The exact emission wavelength and decay time depend on the type of organic activator and on the host material. A large number of different plastic scintillators are available, each for a specific application. General characteristics of plastic scintillators are presented in the physical constants table below.
Plastic scintillators are produced in a wide variety of shapes and sizes. Cast sheets are the most commonly used forms. You also can obtain precision thin sheets, rods, annuli, and large rectangular blocks.
Plastic sheets cast from the monomer ensure the highest light yield and best internal light transmission. All raw materials undergo extensive purification prior to polymerization and the finished sheets exhibit highly uniform scintillation and optical properties. Scintillators are machined to final dimensions using diamond tooling to provide optimum quality surfaces for total internal reflection.
We supply most solid scintillators with their surfaces prepared to optimize light collection. For cast sheets, the cast surfaces are untouched, and the edges are machined and polished or diamond milled. Rods, annuli and blocks are machined and polished or coated with a diffuse reflector paint such as BC-620. Such a reflector is used only when there are few reflections of the scintillation light off the scintillator surfaces before the light reaches the PMT. Most applications require finished surfaces. You can also obtain scintillators as finished detector assemblies. These incorporate light guides, photomultiplier tubes, special radiation entrance windows, and light-tight wrappings (or metal housings).
BC-400 thin sheets, Alpha, Beta | BC-404 fast counting, Alphas, Betas | BC-408 best general-purpose; used in Time of Flight counters | BC-412 has longest attenuation length | BC-416 economy
BC-418 1.4 ns time constant, recommended for use in small sizes | BC-420 1.5 ns time constant, for sheet areas > 100mm2 | BC-422Q quenched with benzophenone to improve timing properties
Intended for use with devices which have optical sensitivities in the green and red portions of the spectrum
Ideal for use with silicon photodiodes and red-enhanced photomultiplier tubes.
High temperature characteristics of polystyrene based scintillators without the diminished light yield.
Formulized for slow decay constant of 285 ns.
Detects low-energy (<100 keV) at high count rates
Physical Constants of Plastic Scintillators
|Scintillator||Light Output %Anthracene1||Wavelength of Maximum Emission, nm||Decay Constant, ns||Bulk Light Attenuation Length, cm||Refractive Index||H:C Ratio||Density||Softening Point °C|
|BC-422Q (Benzephenone,0.5%)||11||370||0.7||< 8||1.58||1.102||1.023||70|
|BC-452 (2% Lead)||48||424||2.1||150||1.58||1.134||1.050||60|
1 Anthracene light output = 40-50% of NaI(Tl)
* 0.1 to 5 weight % also available
** Ratio of Cerenkov light to scintillator light = 10:1