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Liquid scintillation counting is a standard laboratory method in the life-sciences for measuring radiation from beta-emitting nuclides. Scintillating materials are also used in differently constructed "counters" in many other fields. Radiation has a variety of different meanings. ...
Beta particles are high-energy electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. ...
A radionuclide is an atom with an unstable nucleus. ...
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. ...
A scintillation counter measures ionizing radiation. ...
Samples are dissolved or suspended in a "cocktail" containing an aromatic solvent (historically benzene or toluene, but more recently less hazardous solvents have come into favour) and small amounts of other additives known as fluors. Beta particles emitted from the sample transfer energy to the solvent molecules, which in turn transfer their energy to the fluors; the excited fluor molecules dissipate the energy by emitting light. In this way, each beta emission (ideally) results in a pulse of light. Scintillation cocktails often contain additives that shift the wavelength of the emitted light to make it more easily detected. Benzene, also known as C6H6, PhH, and benzol, is an organic chemical compound which is a colorless and flammable liquid with a pleasant, sweet smell. ...
Toluene, also known as methylbenzene or phenylmethane is a clear water-insoluble liquid with the typical smell of paint thinners, reminiscent of the sweet smell of the related compound benzene. ...
The wavelength is the distance between repeating units of a wave pattern. ...
The samples are placed in small transparent or translucent (often glass) vials that are loaded into an instrument known as a liquid scintillation counter. The counter has two photomultiplier tubes connected in a coincidence circuit. The coincidence circuit assures that genuine light pulses, which reach both photomultiplier tubes, are counted, while spurious pulses (due to line noise, for example), which would only affect one of the tubes, are ignored. Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ...
Counting efficiencies under ideal conditions range from about 30% for Tritium (a low-energy beta emitter) to nearly 100% for Phosphorus-32, a high-energy beta emitter. Some chemical compounds (notably Chlorine compounds) and highly colored samples can interfere with the counting process. This interference, known as "quenching", can be overcome through data correction or through careful sample preparation. Tritium (symbol T or 3H) is a radioactive isotope of hydrogen. ...
This article is about the chemical element. ...
General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Atomic mass 35. ...
High-energy beta emitters such as P-32 can also be counted in a scintillation counter without the cocktail. This technique, known as Cherenkov counting, relies on the Cherenkov radiation being detected directly by the photomultiplier tubes. Cherenkov counting in this experimental context is normally used for quick rough measurements, since it is more liable to variation caused by the geometry of the sample. Cherenkov effect at the UMRs nuclear reactor Cherenkov radiation (also spelled Cerenkov) is electromagnetic radiation emitted when a charged particle passes through an insulator at a speed greater than that of light in the medium. ...
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