International Journal of PIXE

PIXE technique has been utilized to analyze some obsidian artifacts found in the Southern Platform of the ceremonial center of Lagunillas, Michoacán, México. According to their chemical composition, the provenance of obsidian was established, thereby confirming the commercial routes of the Lagunillas region during Early (A. D. 900-1200) and Late Postclassical periods (A. D. 1200-1523).

Total suspended particulate (TSP) samples were collected at the west-facing slope (altitude 700 m) of Mt. Moriyoshi in northern Japan, from 24 – 27 June (non-snow-clad period) and 11 – 14 December (snow-clad period) in 1996, with a one-hour sampling interval. The elemental composition and particle shape of TSP samples were determined and/or observed by Particle Induced X-ray Emission (PIXE), a Scanning Electron Microscope (SEM) combined with Energy Dispersive X-ray (EDX) analysis. In the hourly TSP samples collected during the non-snow-clad period, 27 elements were determined. Na, Mg, Al, Si, S, K, Ca and Fe were found to be the major elemental components. On the other hand, 25 elements, excluding Nd and Mo, were found in the snow-clad period samples, and Cl is a dominant element, i.e., a major element, of the snow-clad period samples, unlike the non-snow-clad period. Comparing the arithmetic means of concentrations of major elements in TSP for non-snow-clad and snow-clad periods, Mg, Al, Si, K, Ca and Fe levels in the snow-clad period are 2 – 4 times as much as those in the non-snow-clad period, and 30 times for Na. S is similar. For temporal variation patterns of element concentrations, the non-snow-clad period is different from the snow-clad period. Al, S, Ca, Ti, Fe, Zn and Pb are similar throughout the non-snow-clad period, and Al, Si, Ca and Fe are similar throughout the snow-clad period. With the aid of SEM and EDX analysis, aggregates of car exhaust particles, soil particles and plant spores were observed in the non-snow-clad period samples. In the snow-clad period samples, small silicon-rich spherical particles, aggregates of car exhaust particles and soil particles were observed.

Kidney stones collected from different hospitals in Chennai, south India were analyzed by PIXE with 3MeV protons. The matrix was calcium oxalate and mixture of calcium oxalate and calcium phosphate. Light elements present in minor concentration were P, Cl. Trace elements such as V, Cr, Mn, Fe, Cu, Zn, Sr, Zr & Mo were also present in the stones. Significant amount of Zr was found in one of the samples, Pb and Cd were not present in any of the stones analyzed.

Seventy-five samples of some Indian tobacco-products, 48 blood samples drawn from some tobacco- users and 14 blood samples from some healthy persons without having any tobacco habits were analysed for elements such as K, Ca, Fe, Cu, Zn, Mn, Sr, Se, As and Pb using Energy Dispersive X-ray Fluorescence (EDXRF) spectrometry at the Institute of Physics, Bhubaneswar. Comparison was made between the results from this work and the reported literature values. Tobacco-products were found to be enriched with multi-elements, and it was observed that the human blood-elements were slowly decreasing with respect to their increasing habits of tobacco.

A narrow entrance slit was attached to an in-air high-resolution PIXE system composed of a flat analyzing crystal and a position-sensitive proportional counter. Chemical shift measurements were carried out for Si, P and S Kα_1,2 lines from various sample targets. The precision of measurements is much improved compared with that obtained by the position-sensitive crystal spectrometer system without the entrance slit. The new system equipped with the entrance slit does not require exact sample positioning. It is applicable to non-flat targets. Chemical shift measurements are also possible while moving the targets.

Cross sections of atomic bremsstrahlung of 3p- and 3d- electrons were calculated on the basis of PWBA approximation. By use of present results and formulae previously presented for 1s-, 2s-, 2p-, and 3s- shell electrons, an x-ray spectrum which consists of characteristic x-ray and atomic bremsstrahlung can be obtained theoretically for the element of Z ≤ 50. This method will be very helpful for peak fitting in the PIXE spectrum.

The pre-amplifier with an active reset system was examined to carry out PIXE analysis under the condition that X-rays and back scattered protons are detected simultaneously. Rejection of false signals produced by back scattered protons is discussed, and it is confirmed that false signals can be completely rejected by using an inhibit signal of the preamplifier. Energy resolution of an X-ray detector and a live-time of measurement system were measured as a function of counting rate. As a result, energy resolution did not change and the live-time was 70 % at the high counting rate over 3kcps. The pile-up effect on the X-ray signal with the proton signal tail is also discussed.

The contribution to the atmospheric pollution in Mexico City's conurbation that comes from the northern area has been considered significant for a long time. Therefore, it is important to determine its elemental composition as well as their correlation in sites along the suspected trajectories of airborne particulate matter. Samples were collected simultaneously in two sampling sites along the prevailing wind trajectory in northern Mexico City, and its elemental composition were determined by PIXE. The Sample collection was performed daily from 17 February 14 March 1997 in Xalostoc, an industrial zone in the State of Mexico, and Ticomán within Mexico City. Two samples a day were taken in two periods: 7-19 h and 19-7 h. The samplers used separated particles into two particle size fractions fractions, PM₂₅ and PM₁₅. Three main correlation group of elemental concentrations were determined: fuel combustion, earth crust and industrial origin. The sampling site within Mexico City, Ticomán, was found with an overall tendency of higher elemental concentrations, showing not only influence of local pollution sources, but also that of wind transported particles from neighboring industrial zones such as Xalostoc.