V. Valkovic

Measurement of 14 MeV neutron-induced prompt gamma-ray spectra from 15 elements found in cargo containers

Within the EURopean Illicit TRAfficking Countermeasures Kit (EURITRACK) project, the gamma-ray spectra produced in a series of materials by 14-MeV tagged-neutron beams have been collected in the inspection portal equipped with large volume NaI(Tl) detectors, in order to build a database of signatures for various elements: C, N, O, Na, Al, Si, Cl, K, Ca, Cr, Fe, Ni, Cu, Zn, Pb. The measured spectra have been compared with prediction from Monte Carlo simulations to verify the consistency of the relevant nuclear data inputs. This library of measured 14-MeV neutron-induced gamma-ray spectra is currently used in a data processing algorithm to unfold the energy spectra of the transported goods into elementary contributions, thus allowing material identification.

Trace element characterization of coal fly ash particles

Abstract XRF, PIXE, RBS and STIM were used for a study of trace element distributions in Greek lignites and their ashes. Samples of fly ash collected from electrostatic precipitators have been separated into seven fractional sizes ranging from 300 μm to less than 25 μm. Trace element concentrations show variation as function of grain size. In addition, the results of analyses of 50 individual fly ash particles are presented.

Acquisition of prompt gamma-ray spectra induced by 14 MeV neutrons and comparison with Monte Carlo simulations.

Gamma-ray spectra produced in carbon, nitrogen, oxygen, sodium, aluminium, silicon, chlorine, calcium, chromium, iron, nickel, copper, zinc, and lead by 14 MeV tagged neutrons have been collected with NaI(Tl) detectors of the EURITRACK system, which low-energy threshold has been reduced to 0.6 MeV to detect gamma rays of major elements like iron. The spectra have been compared with Monte Carlo simulations to check the tabulated gamma-ray production data. A quantitative approach to subtract the scattered neutron background is also reported.

Application of proton muprobe analysis to the study of electrostatic precipitation of single fly ash particles

Abstract The development and improvement of technology for the abatement of fly ash emitted by coal-fired power plants can be enhanced by an understanding of particle formation upon coal combustion and of the collection mechanism during precipitation. This requires the chemical and physical characterization of fly ash in terms of both bulk and single particle properties. In this context, μPIXE and RBS analysis using a 1 μm focused beam is very successful in providing major and trace element composition of single particles. In the present work, fly ash particles collected at the inlet and outlet ports of the electrostatic precipitator of a coal-fired power plant have been analysed. In particular, particles with a diameter of about 1 μm, for which the collection efficiency is rather low, have been considered. Results are presented and discussed.

K-shell ionization of V, Cr, Mn, Fe, Co, Ni and Cu by 5-12 MeV carbon ions

Abstract The K-shell X-rays of V, Cr, Mn, Fe, Co, Ni and Cu induced by 12C ions were detected in the projectile energy range 5–12 MeV. From these measurements, experimental K-shell X-ray production cross sections; Kα, Kβ X-ray energy shifts and the K α K β intensity ratios are extracted and presented. Our results are compared with the experimental data obtained previously and with the predictions of the perturbed stationary-state approximation with energy loss, Coulomb, and relativistic corrections (ECPSSR theory). The role of electron transfer to the projectile have been discussed.

Application of X-ray fluorescence spectrometry in assessment of environmental pollution

A conventional X-ray fluorescence (XRF) method as well as total reflection XRF have been applied to the analysis of various environmental materials. Some methodological changes in order to extend the applicability range and improve the accuracy of the XRF analysis are also discussed.

Quantitative PIXE analysis of single fly ash particles by a proton microbeam

Abstract Methods of quantitative PIXE analysis of individual particles in the diameter range between 5 and 10 μm are presented. Two different approaches to the analysis are considered. In the first case, an analysis is performed with a proton mubeam centered at the middle of the particle. In the second case, the beam is scanned over the whole particle. Absorption correction methods were developed for both cases. Advantages and drawbacks are discussed on the basis of analysis of individual fly ash particles.

Optimized sample preparation procedures for the analysis of solid materials by total-reflection XRF

Abstract The total reflection X-ray fluorescence (TXRF) method has been used for the analysis of various types of solid materials of biological, geological and environmental origin. The sample preparation step prior to TXRF measurements has been optimized for the various solid samples, including their decomposition by applying both a microwave oven and a PTFE bomb. Complete procedures for the optimized decomposition from the point of view of speed and completeness of digestion, as well as of the overall precision and accuracy are presented.

USE OF STIM IN THE PROTON MICROPROBE ANALYSIS OF SINGLE PARTICLES

Abstract Scanning proton microprobe data are usually presented as plots of elemental intensity maps. However, these maps do not present actual concentration distributions, due to variations in energy loss and X-ray absorption, caused by local changes of the sample areal density and topology. Scanning transmission ion microscopy (STIM) is the method that can provide additional information of importance for evaluation of these effects. The use of particle shape and areal density distribution, determined by STIM, in the case of single particle analysis is presented in this paper.

Proton microprobe analysis of the trace element distribution in fly ash particles

Abstract The spatial distribution of trace elements in individual coal fly ash particles is an important factor in assessing their environmental impact. The Oxford Scanning Proton Microprobe (SPM) has been used to determine the distribution of elements in fly ash particles with sub-micrometre spatial resolution. PIXE was used to detect the minor and trace elements and simultaneous proton backscattering analysis was used to determine the matrix composition and thickness. Both areal maps and radial line scans of elemental concentrations were obtained. Results are presented and discussed.