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Liquid scintillation counter. Samples are dissolved or suspended in a "cocktail" containing a solvent (historically aromatic organics such as xylene or toluene, but more recently less hazardous solvents are used), typically some form of a surfactant, and "fluors" or scintillators which produce the light measured by the detector.
A scintillator such as zinc sulphide is used for alpha particle detection, whilst plastic scintillators are used for beta detection. The resultant scintillation energies can be discriminated so that alpha and beta counts can be measured separately with the same detector, [8] This technique is used in both hand-held and fixed monitoring ...
Sample loss at trace levels may be due to adhesion to container walls and filter surface sites by ionic or electrostatic adsorption, as well as metal foils and glass slides. Sample loss is an ever present concern, especially at the beginning of the analysis path where sequential steps may compound these losses.
Counting efficiency varies for different isotopes, sample compositions and scintillation counters.Poor counting efficiency can be caused by an extremely low energy to light conversion rate, (scintillation efficiency) which, even optimally, will be a small value.
The SPA technique is dependent on the energy conversion of radioactive decay, which releases light photons which can be detected via the use of some devices such as the photomultiplier tubes of scintillation counters or CCD imagers. This is a very popular technique in practices that require detecting and quantifying radioactivity. [1]
Typically, the capabilities include gamma spectroscopy, low background counting for very thin alpha- and beta-emitting samples, and liquid scintillation counters for extremely low energy beta emitters such as tritium. The DoD directive makes the distinction clear that detection is harder than measurement, and the latter is necessary for MASINT.
The alpha spectra obtained by liquid scintillation counting are broaden because of the two main intrinsic limitations of the LSC method: (1) because the random quenching reduces the number of photons emitted per radioactive decay, and (2) because the emitted photons can be absorbed by cloudy or coloured samples (Lambert-Beer law).
A good example of the difference in energy of the various radionuclei is the detection window ranges used to detect them, which are generally proportional to the energy of the emission, but vary from machine to machine: in a Perkin elmer TriLux Beta scintillation counter , the hydrogen-3 energy range window is between channel 5–360; carbon-14 ...