Search

We developed a 20 MeV particle-induced X-ray emission (PIXE) analysis method using a medical cyclotron, which is conventionally used for positron emission tomography analysis performed in vacuo, during which the target sample is damaged. For non-destructive analysis and ease of switching between target samples, we developed a technique allowing 20 MeV proton PIXE analysis to be performed at the atmospheric pressure. We filled the PIXE analysis chamber with helium and checked that the continuous background of the Compton tails of nuclear reaction γ -rays increased only minimally, and that the quasi-free electron bremsstrahlung (QFEB) did not increase at all, in the X-ray energy spectrum. [ABSTRACT FROM AUTHOR]

We explored whether medical positron emission tomography (PET) cyclotron proton beams could be used for proton-induced X-ray emission (PIXE) analysis. The beam current of the medical PET cyclotron is high, as required for radioisotope production, and is not commonly used for PIXE analysis. We successfully extracted stable proton beams of low intensity by using the ion source of a medical cyclotron to exploit proton impurities in deuteron gas. We performed 20-MeV PIXE analysis of a biological sample (used tea leaves). Elements lighter than Sr could be detected with high sensitivity (< 14 ppm) using a silicon drift detector. We thus showed that a medical cyclotron widely used for PET diagnosis could be employed for PIXE analysis of biological samples. [ABSTRACT FROM AUTHOR]

The amount of contaminated soil with radioactive cesium (Cs) is more than 22 million cubic meters as a result of the Fukushima Daiichi nuclear power plant accident. In order to save the cost for keeping the soil covered, it is necessary to reduce its volume. To seek methods of efficient volume reduction, we investigated the cross-sections of contaminated soil particles using autoradiography (ARG), SEM, particle-induced X-ray emission (PIXE) analysis. The results of ARG showed that the radioactive Cs atoms were distributed on the surface of contaminated soil particle. PIXE analysis showed that K, Fe and Ti were distributed also on the surface of contaminated soil particle. Therefore, it is considered that the radioactive Cs contamination correlated with the distribution of K, Fe, and Ti. Moreover, the result suggests that it is possible to reduce the volume of contaminated soil by peeling off the radioactive Cs contaminated surface of soil. [ABSTRACT FROM AUTHOR]

A system matrix (SM) is the basic component of iterative image reconstruction algorithms. Calculation of the SM needs a considerable amount of time due to an enormous number of lines of response (LORs) being modeled. In this study, we developed a technique based on a piece-wise calculation method in which symmetry and further division of the voxels are applied. The detector response function for all detectable pairs of photons along certain LORs originating from each voxel is calculated analytically. The total number of LORs in 300 × 300 × 120 voxels (with 2 × 2 × 2 mm) is ~44 billion, and the SM was calculated by the use of three different computers independently; the calculation time was 5 h. The SM took 5 days when calculated by the use of the conventional method (where symmetry and the piece-wise method are not used). The sensitivity correction factor was stored; it had a size of 42 MB in a four-byte computer memory. [ABSTRACT FROM AUTHOR]

A lot of radiocesium had been deposited onto pastures and grasslands following Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. More radiocesium was accumulated in root-mat horizon than in both above ground plant bodies and mineral soils. In this study, factors causing higher radiocesium concentrations in root-mat horizon were evaluated by the addition of stable cesium solution and particle-induced X-ray emission (PIXE) analysis. Results suggest that adsorption onto root surfaces played a significant role in Cs accumulation in root-mat horizon. Furthermore, absorption of Cs was key to its long-term preservation. The adsorption of Cs by clay minerals also contributed to its retention. A slow water infiltration rate may also affect the enrichment of radiocesium in root-mat horizon. Based on these results, it is concluded that both biotic and abiotic factors contributed to the effective retention of radiocesium in root-mat horizons following the FDNPP accident. [ABSTRACT FROM AUTHOR]