In this short communication, a recent article published in the Journal of Thermal Analysis and Calorimetry, which presents
an erroneous conclusion based on incorrect calculations, is critically discussed. Since the observations made in that report
are based on part of the content of a publication of my authorship, trying to reject some expressions I presented, obviously
it came to my attention. This brief note emphasizes that some of the arguments used and the main conclusion stressed in the
manuscript under discussion are wrong and must be dismissed.
There are two components involved in evaluating age by luminescence. One is the equivalent dose determined from luminescence measurements on mineral crystals (usually quartz or feldspar) extracted from the material to be dated. The other is the dose rate to which the crystals have been exposed throughout antiquity. The age is then the ratio (equivalent dose)/(dose rate). Factors which influence the accuracy of the two components, and so the accuracy of the age, are discussed. Limiting factors are identified in order to recognize aspects of measurement on which future development must concentrate to achieve an improvement in accuracy of age determination.
An INAA procedure for routine analysis of rock samples is described. Samples are irradiated using a rotating sample holder.
Measurement of the induced gamma activity is performed using an automatic gamma spectrometer and the elemental concentrations
are calculated by a computer. The analytical error is discussed and the precision and accuracy evaluated experimentally. An
average error of ±3–5% without considering counting statistics is obtained. Results for 19 elements in 8 international standard
rocks are reported. A short discussion of the cost of the analysis is included.
Analytical chemists are scientific scavengers, using any available physical phenomenon to determine the composition of materials.
Accuracy, unlike mere reproducibility, depends on understanding the measurement process, most usefully by stressing it until
it bends. The use of neutron capture gamma rays for analysis involves some issues not encountered in conventional neutron
activation analysis which, when understood, extend the utility and reinforce the value of nuclear methods of elemental analysis.
These methods are being increasingly recognized as tools for SI-traceable metrology.
Authors:F. De Corte, A. Simonits, A. De Wispelaere, and J. Hoste
The present paper deals with the accuracy and applicability of the k0-standardization technique in NAA. Topics included are: user-oriented outline of the method, relevant nuclear data (k0, Q0, tc.), the non-1/E epithermal flux distribution, small detector separations and/or extended source geometries, (n, ) reactions with a Westcott-g1, primary interferences, subsequent (interrupted) irradiations, the non-constancy of the neutron flux during irradiation, and a final account of the accuracy. Although the paper is written in terms of the k0-methodology, a good deal of the considerations can be transferred to most types of single-comparator standardization.
Authors:R. Lindstrom, R. Zeisler, and R. Greenberg
The basic assumptions of activation analysis are that the induced radioactivity is proportional to the amount of analyte,
and that the quantity of radioactivity can be related simply to the number of counts observed. Quantitative measurement of
activity (and of its uncertainty) is not always simple, especially when accuracy better than a few percent is sought. Recent
work with 77Ge and 76As has demonstrated that the accuracy of half-lives in the literature is sometimes insufficient. Despite these and other problems,
quantitative understanding and documentation of uncertainties can be accomplished, providing demonstrable quality assurance
and supporting claims of traceability to the Système International.
Four different approaches to PIXE data obtained in repeated measurements on thick standards have been evaluated in terms of precision and accuracy. Both were found to be the best when determinations relative to an external standard were normalized to a composition assumed to be 100% oxides.
This paper describes some highlights from the author’s efforts to improve neutron activation analysis (NAA) detection limits
through development and optimization of radiochemical separations, as well as to improve the overall accuracy of NAA measurements
by identifying, quantifying and reducing measurement biases and uncertainties. Efforts to demonstrate the metrological basis
of NAA, and to establish it as a “Primary Method of Measurement” will be discussed.
The different approaches of the monostandard activation analysis are evaluated critically in order to put them into a common
formulation. The nuclear data relevant to the method, which are selected and verified by experiment, are presented for general
application. The accuracy of the method for multielement analysis is discussed by comparing the analytical results of the
various reference materials from different methods and laboratories with those from monostandard activation analysis.
Gamma-ray spectrometry losses through pulse processing dead time and pile-up are best assayed with an external pulse technique. In this work, the virtual pulse generator technique as implemented commercially with the Westphal loss free counting (LFC) module is set up and tested with four high resolution gamma-ray spectrometers. Dual source calibration and decaying source techniques are used in the evaluation of the accuracy of the correction technique. Results demonstrate the reliability of the LFC with a standardized conventional pulse processing system. The accurate correction during high rate counting, including during rapid decay of short lived activities, has been the basis for highly precise determinations in reference materials studies.