Prompt gamma neutron activation analysis
Encyclopedia
Prompt-gamma neutron activation analysis (PGNAA) 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
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
. 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 application of PGNAA is an online belt elemental analyzer or bulk material analyzer
used in cement
, coal
and mineral
industries.
The technique can be described as follows. The sample is continuously irradiated with a beam of neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
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
Gamma ray spectrometer
A Gamma-Ray Spectrometer, or , is an instrument for measuring the distribution of the intensity of gamma radiation versus the energy of each photon....
. 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 application of PGNAA is an online belt elemental analyzer or bulk material analyzer
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, crossbelt analyzer and elemental analyzer...
used in cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
, coal
Coal analyzer
Coal analyzers are used by coal producers, coal preparation plants and coal-fired power plants to determine coal quality in real time. Coal quality parameters of greatest interest include ash, moisture, sulfur, and energy value...
and mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
industries.
External links
- http://www.ncnr.nist.gov/instruments/pgaa/
- http://ois.nist.gov/nistpubs/technipubs/recent/search.cfm?dbibid=204