I. Uzonyi

Realization of the simultaneous micro-PIXE analysis of heavy and light elements at a nuclear microprobe

Abstract A new in-vacuum micro-PIXE experimental set-up has been realised at an Oxford-type scanning nuclear microprobe facility. It is based on the simultaneous use of an ultra thin windowed detector and a conventional Be-windowed one for the measurement of the characteristic X-rays of light and heavier elements in the E≈0.2–6 keV and E>4 keV energy ranges, respectively. Complete analytical characterisation of samples from carbon to uranium is possible in a single irradiation process. Performance and technical developments are described in detail.

Magnetic spherules: Cosmic dust or markers of a meteoritic impact?

Abstract Magnetic spherules from several localities in Hungary were analyzed and the results were compared to analytical data of similar objects found in Japan, Slovakia and Hawaii. The studies were carried out using micro-PIXE technique. On the basis of morphological features and elemental compositions it was concluded that signs of a new meteoritic impact could be found.

Ion beam dose measurement in nuclear microprobe using a compact beam chopper

Abstract The accurate measurement of ion beam dose is a key point of quantitative analytical methods like PIGE, PIXE or RBS. To solve this problem for our Oxford-type scanning nuclear microprobe (SNM), a small-sized compact beam chopper has been developed. Ion beam dose is derived from the observed RBS yield from the surface of a wing after calibrating the yield versus collected charge. The wing is rotated by a stepper motor and is optionally covered with foils made of Al, Ni or Au. The beam chopper is capable to measure ion beam doses for different ions at a wide range of energy and current with a precision in the order of 1%.

Application of a Clover-Ge-BGO detector system for PIGE measurements at a nuclear microprobe

Abstract The application of a high efficiency Clover–Ge–BGO detector system for PIGE elemental analysis at the Debrecen nuclear microprobe is demonstrated. Advantages and disadvantages of this facility are discussed. Detection limits for Li, B, F, Na, Al and Si in different sample matrixes are presented.

Contribution of PIGE technique to the study of obsidian glasses

Abstract An application of the particle induced gamma-ray emission (PIGE) method with the use of a CLOVER-Ge-BGO detector system (Elekes et al., 1999) for the analysis of source materials of obsidians of archaeological use is reported in this work. Grouping and association of samples resulted via various magmatic processes, with diverse provenances, is detailed based on the light element concentration data. A comparison of PIGE with the laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) on heavier elements is presented.

Calibration of an UTW Si(Li) detector in the 0.28–22.1 keV energy range at a nuclear microprobe

Abstract The efficiency of an ultra thin windowed Si(Li) detector has been determined experimentally in the photon energy range of 0.28–22.1 keV at the Debrecen scanning nuclear microprobe facility. The calibration technique was based on the measurement of thick targets made from pure elements and chemical compounds by PIXE technique. Characteristic X-ray spectra were fitted and PIXE cross-sections were calculated by the new version of the PIXEKLM program package. The efficiency function was determined by fitting the detector parameters in order to minimize the difference between the measured and calculated efficiency values. The accuracy of the method is estimated to be 20–10% in the 0.28–1 keV energy range and 10–5% above 1 keV. An overview of theoretical and experimental aspects of the efficiency calibration procedure will be presented.

Fe-Mn micronodules born in the metalliferous sediments of two spreading centres: the East Pacific Rise and Mid-Atlantic Ridge

Abstract A geochemical study of Fe–Mn micronodules associated with the metalliferous sediments at two spreading centres has shown that their composition depends on the site of micronodule formation. Close to the hydrothermal mounds they exhibit significant variation in elemental content related to the type of hydrothermal discharge (low- or high-temperature), the nature of primary hydrothermal matter (plume fall-out, oxidised sulfides), and the extent of diagenesis. In this environment three types of micronodules can be distinguished although not observed as pure end-members: (1) diagenetic micronodules; (2) micronodules formed generally from the plume fall-out of oxyhydroxide matter; and (3) micronodules grown on the oxidised sulfide grains supplied to the sediments by slumping or fall-out of nearby buoyant plume. Away from the active spreading centre, the hydrothermal signatures of primary precipitates are gradually masked and hydrogenous/diagenetic processes lead the micronodule formation. Composition of micronodules becomes less variable. Well-pronounced, deep rift valleys confine the hydrothermal plume, which brings the hydrothermal suspension into contact with restricted volumes of seawater and, consequently, weakens the hydrogenous influence on the primary hydrothermal matter. Shallow rift valleys do not confine hydrothermal plumes, which are scattered over hundreds of kilometres by bottom currents. This brings the hydrothermal suspended matter into contact with large volumes of seawater. Extensive scavenging occurs, which masks the hydrothermal signal away from the spreading axis and enhances the hydrogenous one. Thus, the ridge crest morphology, defined by the spreading rate, is supposed to play a certain role, though indirect, in the chemical composition of the primary precipitates and, consequently, in the composition of the micronodules formed.

Characterization of Dyrrhachium silver coins by micro-PIXE method

Abstract Ancient silver coins (drachms) issued by the Greek city Dyrrhachium during 68–43 years BC were analysed non-destructively by micro-PIXE method. The selected 27 drachms, including four imitations, belong to the numismatic collection of the Hungarian National Museum (HNM). Nine elements (Fe, Cu, Zn, Br, Ag, Sn, Au, Pb and Bi) were determined quantitatively. Samples are characterised with a uniformly low ∼92% Ag concentration. Debasement is supposed.

Study of cross-sectional and longitudinal distribution of some major and minor elements in the hair samples of haemodialysed patients with micro-PIXE

The concentration of Zn, K, Ca, Fe and Cl was determined in the hair samples of haemodialysed patients and healthy controls. Cross-sectional and longitudinal measurements were performed using the micro-PIXE method. The concentration changes of the above mentioned elements along the length of the hair and their cross-sectional distribution were studied. The effect of the washing procedure on the concentration of these elements has also been determined. The ability of the PIXE method was examined using Human Hair certified reference material (NCS DC 73347), and the results show that this method can be used to determine the concentration of the selected elements in the hair samples. We compared the results of the PIXE method with the results obtained from microwave digested reference material with the ICP-OES method. The concentration ranges of Ca, Fe and Zn were similar in the patients and controls while the concentration ranges of Cl and K were different (controls: Ca, 135-1598; Cl, 394-2382; Fe, 6-51; K, 54-1055; Zn, 102-183 µg g –1 ; versus patients: Ca, 298-559; Cl, 2476-7821; Fe, 15-58; K, 327-2031; Zn, 96-163 µg g –1 ). The washing procedure highly affected the concentration of K and Cl (unwashed: K, 1164±846; Cl, 6107±1714 µg g –1 ; versus washed: K, 497±552; Cl, 3470±1446 µg g –1 ). There were no differences between controls and patients in the cross-sectional distribution of the selected elements; the distribution of Cl was homogeneous, the Ca was concentrated in the outer layer of the hair while the distribution of K was nearly homogeneous with a slight increase at the outer layer.

Investigation of incrusted pottery found in the territory of Hungary by micro-PIXE method

Abstract Incrusted pottery samples from the territory of Hungary were analyzed by micro-PIXE technique. Measurements were executed on the front and back side of the samples and inside the incrustations too. We succeeded to group the pottery from different regions and periods by the composition of the ornament. It was concluded that the elemental composition of the ornament may be characteristic to the provenance of the pottery. In case of samples from Vors-Mariaasszonysziget the presence of a kind of grit in the incrustations with high calcium and phosphorus content was established. The material of the grit is presumably bone. Samples from other archaeological localities can be described by incrustations with different compositions. Incrustations in the samples from Balatonfuzo are presumably composed of limestone (CaCO 3 ), from Baradla cave (Aggtelek) probably of white clay paste (kaolinite). It was also concluded that the red color of the ornaments of some sample from Baradla cave is caused by hematite.