International Journal of PIXE

In this paper, we have proposed monochromatic X-ray microbeams, produced by a proton-induced X-ray technique and a polycapillary X-ray half lens, as a tool for micro-X-ray fluorescence (XRF) analysis. A 30 μm thick planar Cu target was irradiated by a 2.5 MeV proton beam to produce Cu Kα X-rays (8.0 keV), and a polycapillary X-ray half lens was utilized to focus the X-rays emitted behind the Cu target. The focal spot size of the focused X-ray beam was 250 μm at full width at half maximum, which was verified using a knife-edge scanning method. The output focal distance and the depth of focus of the optics were measured to be 47 mm and 1 mm, respectively. A square grid pattern of Co thin films, formed on a thick Cu substrate by thermal evaporation, was used as a test sample for evaluation of the analytical performance of the micro-XRF setup. Two-dimensional mapping of the Co distribution on the Cu substrate was successful, and the spatial resolution was consistent with the beam spot size. For this Co layer, a minimum detection limit of 2.3 ng was achieved.

In this paper, we measured the concentrations and spatial distributions of aluminum and manganese with the growing period of a tea leaf. Both elemental concentrations increased with the growing period and showed a rapid increase between five and six months. Aluminum showed clear localization in the epidermis with the growing period. Manganese did not show clear localization like aluminum throughout the growing period. The spatial correlation between aluminum and manganese were not observed.

Two different kinds of metallic plates on a rotating disk target were irradiated with a MeV proton beam, and quasi-monochromatic pulsed X-rays with different energies around the absorption edge of the contrast medium were alternately produced. By using these dual-energy X-rays and a high-sensitivity X-ray movie camera, we took a motion picture of the transmission image of a periodically moving phantom, which simulated a rat heart as a test animal. We found that the enhanced movie imaging of the contrast agent is available by subtraction between adjacent picture frames.

National Institute of Advanced Industrial Science and Technology is working for the Global Alliance to Eliminate Lead Paint (GAELP) of the United Nations Environment Program (UNEP), under the cooperation of Iwate Medical University Cyclotron Center and Nishina Memorial Cyclotron Center of Japan Radioisotope Association. In order to demonstrate how the PIXE is useful to monitor lead in human body, hair samples were collected from local communities and analyzed by the PIXE at the University together with the control of office workers. The analysis showed a clear anomaly of lead for factory workers. It is recommended that the PIXE be added as one of the instruments to assist UNEP's lead and other heavy metal studies.

The aim of this study was to determine whether oxygen-releasing microcapsules could be used to sensitize cancer cells to kill by radiation. The microcapsules were generated by spraying a mixture of 0.1% alginate and hyaluronic acid into a 0.3 mmol/l solution of CaCl₂ and FeCl₂. These were then subcutaneously injected around a MM48 tumor (a cell line derived from human breast cancer) in the left hind legs of C3H/HeN mice, and tumors were dosed with ⁶⁰Co γ-ray radiation. We showed that the oxygen released from the microcapsules enhanced the anti-tumor effect of radiation treatment via the generation of oxygen radicals.

Multiwavelength optics was improved to create a high-resolution ion luminescence (IL) spectroscopy system. An electrically cooled back-thinned CCD array with an effective wavelength range from 200 nm to 980 nm was used for the IL detector. The spectra of IL were acquired during microbeam irradiation of targets with 3 MeV H⁺ ions. The IL spectroscopy system provides IL spectra with a wavelength resolution of approximately 2 nm. IL spectroscopy was combined with in-air micro-particle-induced X-ray emission (micro-PIXE) at a beam current of approximately 100 pA, and a specific analysis allows us to determine the chemical composition of the target. Compared with the conventional wavelength-dispersive IL systems, the proposed IL spectroscopy system is more sensitive to IL, making it possible to observe the changes in spectra that correspond to changes in the chemical state of the elements inside the target.

In this paper, a two-detector measuring system in in-air PIXE system composed of two Si(Li) detectors has been developed for simultaneous measurement of low- and high-Z elements. In order to improve detection sensitivity of the detector for low energy region, a new device which is attached at the tip of the detector has been designed. It is made of acryl and has a thin end on which a 1.5 μm-thick Mylar film is stuck. As a result, it exhibited a miraculous effect in improving detection sensitivity at low energies and it became possible to detect K X-rays of aluminium. In order to perform quantitative analysis in in-air system, we have measured detection efficiencies for the two Si(Li) detectors including the effect of X-ray absorption in air on the basis of the method that we developed. Concerning the beam energy at the target and corresponding X-ray production cross-sections, the same values as were reported in the previous paper were applicable since conditions of irradiating system were unchanged. It was confirmed that the new method allows us to quantitatively analyze all the elements heavier than aluminum and to obtain mostly the same results as those by in-vacuum PIXE for various kinds of samples. Accuracy of analysis was also confirmed by using a standard material.

The microbeam system at Tohoku University has various applications. Recently higher spatial resolution down to several hundred nm and higher beam current with the resolution of several μm were required. To meet these requirements, a triplet lens system was installed. While the triplet system has higher demagnification, the chromatic aberration is much larger than in the doublet system. To achieve better performance in the triplet system, improvements in the energy resolution of the accelerator are required. Various sources of accelerator voltage ripples were investigated. The high voltage generating circuit was symmetrized and the noise components were reduced to minimize the voltage ripple. The voltage ripple of the accelerator for low-frequency components was reduced to around 70 V. The voltage ripple of the 120-kHz component was 140 V_p-p.