International Journal of PIXE

PIXE analysis was applied to estimate mineral concentration in red sea bream otoliths without cutting or polishing. Detected elements include Sr, Fe, Mn and Zn, which are commonly found in the otoliths in marine fishes. Strontium-Calcium concentration ratio is calculated by means of combined X-ray yields. The ratio doesn’t indicate dear correlaion with mean reared seawater temperature. It is caused by the diffraction error induced by rough topographies of the otoliths surface.

A few attempts have been done to reduce ambiguous factors in the analysis of complex x-ray spectra. Uncertainty in peak identification and separation due to overlapping of x-ray peaks can be reduced by taking into account the response function of x-ray peaks and by using peak functions including all the x-ray sub-lines in a x-ray series. Ambiguous factors due to discontinuity of backgrounds which is sometimes followed by huge peaks can be reduced by considering contributions from the pile-up, escape and tail functions. The problem of uncertainty in the background fitting in a region of low x-ray energy, where many peaks overlap each other and determination of the background function contains much difficulties and ambiguities, can be solved by using peak functions involving tails in place of Gaussians.

Using PIXE we determined concentrations of iron, nickel, copper, zinc, selenium, and rubidium in sera of 24 patients with acute myocardial infarction and 12 healthy controls. Rubidium*, selenium*, zinc**, nickel** and iron** concentrations are significantly (P<0.001*, P<0.01**) lower for patients than for control subjects. No significant difference is observed in the copper content. However, there is a slight increase in copper content in the patients so that the ratios Cu/Rb, Cu/Se, Cu/Zn, Cu/Ni, Cu/Fe are significantly higher for the patients than for the control subjects (P<0.01).

Trace elements in soy sauce have been measured by means of in-air PIXE. Six kinds of trace elements were detected, such as Mn, Fe, Ni, Zn, Cu and Br. Concentrations of Mn, Fe, Zn and Br which were observed in all samples, have been determined. Bach analyzed sample contained considerable amount of Br about 160 ppm. Comparison of Br content of the imported raw materials with those of the domestic ones suggested that the large amount of Br was the residual fumigation chemicals in the imported raw materials.

A possibility of using an X-ray from incident ions in micro PIXE measurement with MeV heavy ions was discussed. To reveal the feature, a Cu-Ti plate was analyzed by a 5 MeV silicon and a 5 MeV nickel ion microprobe and the PIXE-mapping images of the X-rays from the incident ions were compared with the normal PIXE-mapping images of the X-rays from the target. These images indirectly reflected the distribution of a specific element with good statistics.

The characteristics of the road-side particles were examined. The elemental concentrations of aerosol particle collected on the road-side were measured both by PIXE analysis as a bulk sample and SEM-EDX analysis as individual particle sample. For the data set of SEM-EDX, cluster analysis was applied.

On an average, more than 80% of the aerosol particles are consisted of lighter elements such as C, O, N and H. Main metal components contained in the roadside particles were Si, Ca, Fe and Al that were mainly originated in soil.

In NMCC(Nishina Memorial Cyclotron Center) we are doing researches on PET of nuclear medicine (Positron Emission Computed Tomography) and PIXE analysis (Particle Induced X-ray Emission) using a small cyclotron of compactly designed. The NMCC facilities have been opened to researchers of other institutions since April 1993. The present status of NMCC is described.

Bio-samples (medical samples, plants, animals and environmental samples) have mainly been analyzed by PIXE in NMCC. Small amounts of bio-samples for PIXE are decomposed quickly and easily in a sealed PTFE (polytetrafluoroethylene) vessel with a microwave oven . This sample preparation method of bio-samples also is described.

An ultra compact cyclotron was constructed for Particle Induced X-ray Emission (PIXE) and Rutherford Back Scattering (RBS) experiments. The cyclotron accelerates proton and alpha-particle beams to a constant energy of 3 MeV. The size of the magnet is 85cm×85cm×60cm. Characteristics of the cyclotron are presented.

The procedures for the estimation of background and the analytical representation of peak shape are described. The method for the background evaluation is outlined without using peak-free regions in spectrum. The expression for the response function is simple and reproduces experimental data for a wide range of channel numbers and peak positions.

The contributions of ECC, ELC and TI to cusp electrons are measured from 40 keV to 100 keV of projectile He⁺ energies. While the contribution of the ELC is so small and decreases as the energy of projectile decreases, the contribution of TI increases slowly and becomes constant finally.

The ratio of the contribution of TI to that of ECC remains approximately constant in the energy region. This fact implies that there is a linear correlation between the cusp electrons of processes TI and those of ECC.