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(physics) a flash of light that is produced in a phosphor when it absorbs a photon or ionizing particle
the twinkling of the stars caused when changes in the density of the earths atmosphere produce uneven refraction of starlight
a brilliant display of wit

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火花,きらめき / 才気のひらめき

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/05/14 16:09:22」(JST)

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Liquid scintillation counting is the measurement of activity of a sample of radioactive material which uses the technique of mixing the active material with a liquid scintillator, and counting the resultant photon emissions. The purpose is to allow more efficient counting due to the intimate contact of the activity with the scintillator. It is generally used for alpha and beta particle detection.

Technique

Liquid Scintillation Counter

Samples are dissolved or suspended in a "cocktail" containing a solvent (historically aromatic organics such as benzene or toluene, but more recently less hazardous solvents are used), typically some form of a surfactant, and small amounts of other additives known as "fluors" or scintillators. Scintillators can be divided into primary and secondary phosphors, differing in their luminescence properties.

Beta particles emitted from the isotopic sample transfer energy to the solvent molecules: the π cloud of the aromatic ring absorbs the energy of the emitted particle. The energized solvent molecules typically transfer the captured energy back and forth with other solvent molecules until the energy is finally transferred to a primary scintillator. The primary phosphor will emit photons following absorption of the transferred energy. Because that light emission may be at a wavelength that does not allow efficient detection, many cocktails contain secondary phosphors that absorb the fluorescence energy of the primary phosphor and re-emit at a longer wavelength.

The radioactive samples and cocktail are placed in small transparent or translucent (often glass or plastic) vials that are loaded into an instrument known as a liquid scintillation counter. Newer machines may use 96-well plates with individual filters in each well. Many counters have 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.

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.

High-energy beta emitters, such as phosphorus-32, can also be counted in a scintillation counter without the cocktail, instead using an aqueous solution. 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 the geometry of the sample can create variations in the output.

References

Handbook of liquid scintillation spectrometry
Liquid Scintillation Counting, University of Wisconsin–Milwaukee Radiation Safety Program
Principles and Applications of Liquid Scintillation Counting, National Diagnostics
K. Rengan, "Cherenkov counting technique for beta particles: advantages and limitations". J. Chem. Educ., August 1983, 60 (8), 682-684. doi:10.1021/ed060p682

UpToDate Contents

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English Journal

A prototype of a portable TDCR system at ENEA.

Capogni M1, De Felice P2.
Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine.Appl Radiat Isot.2014 Nov;93:45-51. doi: 10.1016/j.apradiso.2014.03.021. Epub 2014 Mar 26.
A prototype of a portable liquid scintillation counting system based on the Triple-to-Double Coincidence Ratio (TDCR) technique was developed at ENEA-INMRI in the framework of the European Metrofission project. The new device equipped with the CAEN digitizers was tested for the activity measurements
PMID 24709003

First TDCR measurements at low energies using a miniature x-ray tube.

Halter E1, Thiam C2, Bobin C3, Bouchard J2, Chambellan D4, Chauvenet B2, Hamel M5, Rocha L5, Trocmé M5, Woo R5.
Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine.Appl Radiat Isot.2014 Nov;93:7-12. doi: 10.1016/j.apradiso.2014.03.007. Epub 2014 Mar 18.
Developed for radionuclide standardization using liquid scintillation, the Triple to Double Coincidence Ratio (TDCR) method is applied using coincidence counting obtained with a specific three-photomultiplier system. For activity determination, a statistical model of light emission is classically us
PMID 24685767

Determination of (210)Pb and (226)Ra/(228)Ra in continental water using HIDEX 300SL LS-spectrometer with TDCR efficiency tracing and optimized α/β-discrimination.

Eikenberg J1, Beer H2, Jäggi M3.
Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine.Appl Radiat Isot.2014 Nov;93:64-9. doi: 10.1016/j.apradiso.2014.02.021. Epub 2014 Mar 3.
An analytical method for determination of (210)Pb, (226)Ra and (228)Ra is presented based on adsorption on 3M Empore RadDiscs, and measurement applying liquid scintillation spectrometry (LSC) after elution. The LSC measurement was performed with optimized α/β-discrimination and isotope standardiza
PMID 24637085

Japanese Journal

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櫻井敬久
Radioisotopes 61(2), 87-93, 2012-02
NAID 40019181830

NaI(Tl)シンチレーションサーベイメータによる穀物試料の放射性セシウム測定 : 環境放射線の遮へい効果とGe半導体検出器測定との相関

亀谷宏美,萩原昌司,根井大介,柿原芳輝,木村啓太郎,松倉潮,川本伸一,等々力節子
日本食品科学工学会誌 : Nippon shokuhin kagaku kogaku kaishi = Journal of the Japanese Society for Food Science and Technology 58(9), 464-469, 2011-09-15
つくば市内の研究所の環境放射線レベルを例に，NaI (Tl）シンチレーションサーベイメータによるγ線測定における環境中の放射線の鉛遮へい体による低減効果を検証した．また，大麦試料を用いて，適切な鉛遮へい体の使用条件下で，検出下限を超える正味計数率と暫定規制値以下の放射性セシウム濃度との関係に相関があることを実証した．
NAID 10029722755