Prompt-gamma neutron activation analysis (PGAA) is a very widely applicable technique for determining the presence and amount of many elements simultaneously in samples ranging in size from micrograms to many grams. It is a non-destructive method, and the chemical form and shape of the sample are relatively unimportant. Typical measurements take from a few minutes to several hours per sample.
The technique can be described as follows. The sample is continuously irradiated with a beam of
neutron
The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...
s. The constituent elements of the sample absorb some of these neutrons and emit
prompt gamma rays which are measured with a
gamma ray spectrometer
A gamma-ray spectrometer (GRS) is an instrument for measuring the distribution (or spectrum—see figure) of the intensity of gamma radiation versus the energy of each photon.
The study and analysis of gamma-ray spectra for scientific and techni ...
. The energies of these gamma rays identify the neutron-capturing elements, while the intensities of the peaks at these energies reveal their concentrations. The amount of analyte element is given by the ratio of count rate of the characteristic peak in the sample to the rate in a known mass of the appropriate elemental standard irradiated under the same conditions.
Typically, the sample will not acquire significant long-lived radioactivity, and the sample may be removed from the facility and used for other purposes. One of the typical applications of PGAA is an online belt elemental analyzer or
bulk material analyzer The term bulk material analyzer is the generic noun for that device which fits around a conveyor belt and conducts real-time elemental analysis of the material on the belt. Other names often found for such a device include ''belt analyzer'', ''cros ...
used in
cement
A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement mix ...
,
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when dea ...
and
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...
industries.
[Harder, J. 2009, 'Material analysis for process control in cement plants', ZKG INTERNATIONAL, 6/7 - 2009, Volume 62, p. 64]
References
*
External links
* https://www.nist.gov/manuscript-publication-search.cfm?pub_id=903948
Video on the PGAA-NIPS at the Budapest Neutron Centre
Analytical chemistry
Neutron
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