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Decay Analysis
Identification of an unknown radionuclide by measuring the decrease in radioactivity.

See also Decay.
Neutron Activation Analysis
(NAA) Neutron activation analysis is a very sensitive analytical technique to determine even very low concentration of chemical elements, trace elements for example, in small biological samples.
NAA becomes commercial available in the USA in 1960.
In the activation process stable nuclides in the sample, which is placed in a neutron beam (neutron flux, 90-95% are thermal neutron with low energy levels under 0.5 eV), will change to radioactive nuclides through neutron capture (artificial radioactivity). These radioactive nuclides decay by emitting alpha-, beta-particles and gamma-rays with a unique half-life. Qualitative and quantitative analysis of the sample is done with a high-resolution gamma-ray spectrometer.
NAA is subdivided into the following techniques:
Fast NAA (FNAA): about 5% of the total flux consists of fast neutrons (energy above 0.5 MeV). As a consequence the radiation contains more nuclear particles.
Prompt Gamma NAA (PGNAA): gamma rays are measured during neutron activation. For detection of elements with a rapid decay.
Delayed Gamma NAA (DGNAA): conventional detection after the neutron activation.
Epithermal NAA (ENAA): ~ 2% of the total neutron flux with an energy level between 0.5 eV and 0.5 MeV are detected inside a cadmium or boron shield.
Instrumental NAA (INAA): automated from sample handling to data processing. Analyzes simultaneously more than thirty elements in most samples without chemical processing.
Radiochemical NAA (RNAA): After neutron activation the sample is chemically refined for better analysis.
Neutron Activation
A sample is placed into a concentrated beam of neutrons. Through neutron-capture heavier nuclei become frequently unstable. This artificial radiation decays with a characteristic half-live consisting of alpha- and beta-particles and gamma-rays.

See Neutron Activation Analysis
Activation
Activation is the production of radionuclides (instable atoms) by bombarding atomic nuclei (stable atoms) with radiation (e.g., photons, neutrons, alpha particles).
With the activation of an atom its decay starts.

See Neutron Activation, Neutron Activation Analysis.
Epithermal Neutron
Epithermal neutrons are unbound moderately severe neutrons. The energy of epithermal neutrons is in the range from 0.025 to 1 eV. Unbound neutrons are produced in fission and in some radioactive decay processes.

See also Neutron Activation Analysis, Neutron Capture.
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 [last update: 2023-11-06 02:01:00]