International Journal of PIXE

High resolution L X-ray emission spectra of Cu have been measured for 0.75 MeV/u H, 0.075 and 0.75 MeV/u F, and 0.075 and 0.64 MeV/u Si ion impacts with a Bragg crystal spectrometer. The high resolution X-ray spectra from the Cu thick target for Lι, Lη, Lα_1,2, Lβ₁, and Lβ_3,4 transitions induced by ion excitation are obtained. The X-ray spectra produced by F and Si ion impacts have complicated structures due to multiple L and M shell vacancy production. The L X-ray emission spectra produced by heavy ion impact are compared with the calculated ones based on the Hartree-Fock-Slater method. The origin of the broadening of the L X-ray transition lines to the higher energy side for heavy ion impact is attributed to one 2p plus multiple 3p and 3d electron vacancy production.

Numerical calculations of the effect of the finite dimensions and orientations of source and crystal are presented for plane and von Hamos Bragg crystal spectrometers for PIXE analysis, combined with a position sensitive (X-ray) detector. Analytical studies of all effects are provided. It is shown that some parameters can produce line shifts and asymmetries. A numerical model for an X-ray diffraction ray-tracing procedure for a crystal Bragg spectrometer is described.

PIXE was adopted for analysis of trace elements in teeth of two species of cetaceans, sperm whale (Physeter macrocephalus) and pantropical spotted dolphin (Stenella attenuata). The analyses were performed along with the growth layer of the teeth, which is formed annually, suitable for age determination. Mn, Fe, Cu, Zn and Sr were detected in the teeth of sperm whale and pantropical spotted dolphin. Among these trace elements, gradual increase was observed for Zn/Ca ratio in the sperm whale's teeth.

Trace elements in squid statoliths were analyzed by PIXE for the following fourteen species in five families of different habitat origin: Ommastrephidae, Ommastrephes bartrami, Dosidicus gigas, Sthenoteuthis oualaniensis; Gonatidae, Gonatopsis makko, G. borealis, Berryteuthis magister; Loliginidae, Loligo bleekeri, L. duvaucelii, L. chinensis, L. edulis and Sepioteuthis lessoniana; Sepiidae, Sepia aculeata and Sepiella inermis; Sepiolidae, Rossia pacifica, Manganese, iron, copper, zinc and strontium were detected from statoliths of all species examined. Among these trace elements, Sr is the highest in concentration. Variation of statoliths Sr concentration reflects taxonomic position and the habitat of specimens. In Ommastrephids and Gonatids, that have oceanic habitat, statoliths Sr concentration is relatively high whereas that of Loliginids and Sepiids, that have coastal habitat, is comparatively low. This fact supports our previous report on this subject. R. pacifica exceptionally shows high statoliths Sr concentration although this species inhabits in coastal water.

Japanese sea bass (Lateolabrax japonicus) is a typical euryhaline marine fish and frequently migrates from salt to freshwater environments during early life stages. We hypothesized that strontium concentrations in the otolith could be a useful index to examine freshwater entry because of its lower concentration in freshwater. Otoliths of Japanese sea bass juveniles collected in the Chikugo river and estuary were analyzed by Particle Induced X-ray Emission (PIXE) to see relationship between strontium concentration and ambient salinity. Strontium concentrations in otoliths of sea bass juveniles are significantly lower in the river samples than in brackish water samples.

PIXE was adopted for analysis of trace elements in otoliths of Masu salmon Oncorhynchus masou masou to examine relationship between trace elements and environmental salinity. The otoliths were removed from salmon juveniles reared in four values of salinity and wild ones. The otolith Sr concentrations of reared individuals are positively related to salinity and there is significant difference between freshwater and seawater. The otoliths of smolts contain more Sr than those of parrs. It seems that the Sr concentrations in otoliths of Masu salmon reflect salinity where they had stayed and show the migration pattern.

A standard-free method developed by ourselves has been applied to bio-medical samples of less than 1 mg or less than 1 μl, to which an ordinary internal standard method can not be accurately applied. As the result, correct values of potassium concentration in NIST-Bovine liver samples of nearly 0.5 mg were obtained. Furthermore, the standard-free method has been applied to small quantity of serum and whole-blood samples, and satisfactory results were obtained. For samples which easily peel off from a backing film, such as serum and whole blood, a carbon tape with an adhesive agent was also used as a backing film, and it is found that this method is also applicable. Moreover, the standard-free method was confirmed to be effective for a case where a specially designed x-ray absorber is used.

We have installed a new in-air PIXE system which has been connected after an existing in-vacuum PIXE course at NMCC (Nishina Memorial Cyclotron Center). Some samples which cannot be placed under a vacuum condition: A living plant and samples of engine oil were measured successfully using the in-air PIXE. The in-air PIXE system as well as the results of the experiments are described.

A thin passive titanium dioxide, in its stoichiometric form, has a very high corrosion resistance, but the same conclusion can not be made on corrosion resistance of a surface which is not stoichiometrically titanium dioxide, or even a surface which is a composition of various elements and oxides. In practice, the implants available on the market have an oxide surface contaminated with other elements. The aim of this paper is to correlate clinical observations that show the deterioration of Ti made implants after certain period of insertion in the patients, and in vitro corrosion resistance of Ti implants with surface passive oxide layer. For this purpose, surface analysis of the retrieved failed implants were performed and in vivo animal experiments with relation to ion release from implants were done. Finally, on the basis of the clinical observation, in vivo animal test, and in vitro electrochemical corrosion test, a model is proposed to explain the corrosion and ion release from the Ti implant.

The purpose of this study is to analyze quantitatively trace elements in human organs without decomposing samples. A palladium thin layer was deposited onto a sample on carbon adhesive tape using a metal ion sputtering equipment. The Pd film was used as an internal standard to determine concentrations of trace elements in human liver. Bovine Liver was applied as the reference standard. Five elements Cu, Zn, Mn, Se and Fe were measured by this method. The values of Copper, Zinc and iron concentrations determined by PIXE using this method agree well with those by ICP-AES. It can he asserted that this method is quite useful in the study of non-destructive PIXE analysis.

PIXE technique was applied to the measurement of elements in the placenta, maternal blood and cord blood of human. The elements determined in these samples include Cl, K, Ca, Fe, Cu and Zn. The values obtained by PIXE were compared with those by ICP-AES to test the accuracy of the method. In placental samples, the mean values of K, Fe, Cu and Zn concentrations obtained by the two methods agree, while Ca concentration is lower in PIXE analysis. The values from PIXE, however, show larger variations resulting from inhomogeneity of the placental samples composed of various tissues different in histological functions. In the analysis of blood samples, the results of the two methods agree for Cl, K, Ca, Fe, Cu and Zn, although the standard deviations tend to be larger in PIXE. These results indicate that PIXE is a useful method for the determination of elements in placental and blood samples, although the preparation to homogenize sample is necessary to obtain accurate results.

We measured intestinal permeability of mice by PIXE method. A mixture of a rubidium chloride solution and a manganese chloride solution was administered orally into mice. The blood was sampled successively after the administration, and the element contents in the blood were measured by PIXE method. The Rb content in the plasma of Rb+Mn administered group reaches maximum 5 min after the administration and decreases subsequently. The value in the whole blood of Rb+Mn administered group increases slightly for first 30 min after the administration and remarkably from 3 hrs. This increase continues for 48 hrs. That in control group is very little. Rb is probably transferred into plasma from intestinal mucosa at first, and subsequently moves into blood cells. The Mn content in control group is little. The values in the whole blood and the plasma of Rb+Mn administered group reach maximum 5 min after the administration and then decrease, and turn to decline to control level at 24 hrs. Mn is probably transferred into blood from intestinal mucosa throughout, and washed out more rapidly than Rb.

The element contents of Rb and Mn in the plasma of Rb+Mn administered mice are found to increase to the peak level 5 min after the administration. Rb and Mn are useful as a tracer to study of intestinal disease with measurement by PIXE method. With this manner by PIXE method, intestinal permeability can be measured more briefly than existing methods. In order to assess intestinal permeability, we propose an indicator which is obtained by comparing the element amounts of Rb and/or Mn in blood sampled just after the administration.

Yonezawa et al. found an induction of yet unknown defence mechanisms(s) in mice which acquired radioresistance two weeks after small dose X-irradiation of 50 cGy. This study here was planned to find some keys to elucidate mechanism of the acquired radioresistance. Metal ions are well known to be important for enzyme activities as well as for metabolisms. Elements from Na to S were analyzed in identical mice sera used previously for the analysis of other heavier eleven elements. The analysis shows that decreases in P and S concentrations on 10 days after the 2nd irradiation of 5.0 Gy are prevented together with potassium reported previously. Contrary, on the 15th day, P and S decrease much compared with the control.

Some small fragments of rag paper - made more than a thousand and a few hundred years ago, and excavated at Turfan, west of China by the Otani-expedition dispatched there during the late Meiji and the Taisho eras - were measured by PIXE. Bromine was highly Detected in all these ancient fragments and modern paper samples that had been placed together with these Turfan manuscripts. In other paper samples, bromine could not be detected (H⁺, 4MeV, 50μC and H⁺, 2MeV, 100μC) and their average concentration was about 1.1ppm (S.D.=1.11ppm, N=15, 0.3~3.4ppm). The bromine contamination of ancient sutras is mainly caused by larvicide of methyl bromide, and the observation suggests that the ancient manuscripts might be spoiled gradually by agricultural chemicals for protecting them from vermin.

A high time-resolution system for dry deposition measurement was developed. This employed a modified beta-attenuation dust monitor and PIXE analysis in order to characterize the process of dry deposition. It was demonstrated that PIXE analysis can detect the presence of Al, Si, S and Fe in dry deposition samples for a one-hour sampling time.

We have applied the micro-PIXE technique to determining the cadmium content in sphalerite (ZnS) and galena (PbS) for use in geothermometry in the Bulawan gold-silver telluride deposit, Philippines. This geothermometry is based on the temperature control on the cadmium distribution between sphalerite and galena. For the analyses by the micro-PIXE, a beam of 3MeV protons was used at CSIRO, Sydney. The size of the beam was between 10-30μm such that during analysis, points within sphalerite-galena pairs which are located very close to the rims of the grains were analyzed and also pairs which are located farther away from each other. The X-rays obtained were deconvoluted for peak areas and converted to concentration using the Geo-PIXE software. The results for rim and non-rim pairs are indistinguishable. The micro-PIXE was capable of analyzing Cd to the level of about 100ppm in galena and 150ppm in sphalerite. Six pairs of galena-sphalerite at the earliest stage of mineralization were examined and only three pairs could be used for our purpose. The obtained temperatures, 402 to 527°C are about 90 to 210°C higher than estimates for the later stage of mineralization in the deposit. Thus, using micro-PIXE we concluded that deposition of early sphalerite and galena in the Bulawan deposit probably occurred at around 500°C before waning down to around 300°C.

Natural FeTiO₃ (illuminate) and synthesized FeTiO₃, single crystals were characterized by Rutherford backscattering spectroscopy combined with channeling technique and particle-induced x-ray emission (RBS-C and PIXE). The results obtained by the ion beam analysis were supplemented by the x-ray diffraction analysis to identify the crystallographic phase. Oriented single crystals of synthesized FeTiO₃ were grown under the pressure control of CO₂ and H₂ mixture gas using a single-crystal floating zone technique. The crystal quality of synthesized FeTiO₃ single crystals could be improved by the thermal treatment but the exact pressure control is needed to avoid the precipitation of Fe₂O₃ even during the annealing procedure. Natural FeTiO₃ contains several kinds of impurities such as Mn, Mg, Na and Si. The synthesized samples contain Al, Si and Na which are around 100 ppm level as impurities. The PBS-C results of the natural sample imply that Mn impurities occupy the Fe sublattice in FeTiO₃ or in mixed phase between ilmenite and hematite.

In this paper a method concerning the measurement of film thickness using PIXE analysis through computer simulation is described. Because of continuously decreasing cross sections for X-ray production by irradiation with the decreasing energy of the incident beam, PIXE has some potentiality to measure film thickness through computer simulation. Ratio of intensities of X-rays of two different elements is sensitive to the changes of energy and geometrical parameters, therefore by changing ion beam energy or the geometrical parameters, we can determine the film thickness to a good accuracy. This method doesn't require any kind of absolute calibration of experimental parameters, as only the ratios of X-ray intensities are taken into consideration. Therefore the inaccuracy in the procedure is only of statistical origin. A titanium film on molybdenum substrate is used as an example of the method. Preliminary result on a very thin Cr/Nd/Fe multilayer film on silicon substrate is presented to show the advantages and possible use of the method. More complex samples, such as multilayer samples with several elements in each layer, can be dealt with the same means too.