Particle Activation Analysis CPAA

In CPAA, the incident charged particle induces nuclear reactions which produce radionuclides, and the characteristic decay radiation of the latter is measured. Qualitative analysis of the radionuclide is achieved by measuring its energy and/or 

CPAA may be employed to determine trace element concentrations in bulk solid material, but its importance in our present context is that it permits the characterization of a thin surface layer, i.e. the mass of the analyte element per surface unit, with a good detection limit and outstanding accuracy. For example the composition of a surface layer (or foil) of known thickness can be determined, or, conversely, the thickness of a surface layer of known concentration. Depth profiling or scanning is not possible, and a disadvantage of the method is that heating occurs during irradiation. It is also not possible to discriminate between different oxidation states of the analyte element or between different compounds. 

De Neve et al. (2000) have carried out a feasibility study to investigate the possibilities and limitations of CPAA as a thin layer characterization method (rather than for the determination of elemental concentrations in bulk samples). The required experimental conditions are (a) that the surface layer containing the analyzed element is thinner (1 pm or less) than the range of the charged particles used and (b) that the substrate (i.e. the layer on which the thin layer is deposited) does not contain the element(s) to be analysed. 

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Charged particle activation analysis (CPAA) is based on charged particle induced nuclear reactions producing radionuclides that are identified and quantified by their characteristic decay radiation. CPAA allows trace element determination in the bulk of a solid sample as well characterization of a thin surface layer. 

The purpose of this study is to apply the unique technique of Charged Particle Activation Analysis (CPAA) to distinguish the characteristics of the oxidation process from a different point of view and define parameters which can be determined by this technique. The parameters to be determined are (1) the kinetics of the adsorption of oxygen containing species, (2) the elemental composition of the oxide layer and how deeply it extends into the particle, and (3) the number of reactive sites on or near the surface. 

Kinetic Experiments. The technique of Charged Particle Activation Analysis (CPAA) for analysis of oxygen in coal has been described previously (J3). In the experiments to study the adsorption of oxygen onto the coal, a slight modification of this procedure has been used. Small lumps of coal were transferred in... 

In radiochemical activation analysis (RAA), the various techniques of activation analysis (AA), i.e., neutron activation analysis (NAA), photon activation analysis (PAA), and charged particle activation analysis (CPAA) are combined with radiochemical separation procedures with the intention of extending the capabilities offered by the purely instrumental methods. 

Although NAA and PAA have a few characteristics in common with charged-particle activation analysis (CPAA), there are fundamental differences, owing to the electric charge of the bombarding particle. 

Acronyms CPAA (charge particle activation analysis)... 

CPAA Charged particle activation analysis PIXE Particle-induced X-ray emission... 

CPAA charged-particle activation analysis E element... 

NAA (neutron activation analysis) is similar to CPAA but uses thermal neutrons, (typically from a nuclear reactor), to activate the sample rather than charged particles. In general, the detection limits of NAA are in the range 10 —10 g. 

For most charged particle-induced reactions the atomic number of the radionucHde B is different from that of the analyte element A. This is the case for (p,n), (p,a), (d,n), (d,a), ( He,n), ( He,d), (o,n), and (a,d) reactions, but not for (p,d) and ( He,a) reactions. The radiochemical separation to be developed for CPAA is thus different from that for all non-nuclear analytical methods and for some other methods based on activation analysis, such as thermal- and fast-NAA (using the (n,y) and (n,2n) reactions, respectively) and PAA (using the ( y,n) reaction). Also, in principle, it is not necessary to separate the matrix, but rather the radionuclide(s) formed out of the matrix element(s). Again, the atomic number of the radionuclide(s) is usually different from that of the matrix element(s). Owing to the chemical separation involved, CPAA is considered to be an independent analytical method, not subject to the same systematic errors as other analytical methods. 

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