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- Author or Editor: K. Masumoto x
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Abstract
We studied the production of nine typical organic analytical reagents labeled with11C,13N and18F by irradiation with charged particles and bremsstrahlung and the purification of labeled compounds with HPLC and sublimation. As a result, we found that six reagents, α-naphthol, β-naphthol, quinoline, α-nitroso-β-naphthol, 8-hydroxyquinoline, and 1,10-phenanthroline H2O could be labeled with11C by bombarding a mixture of each reagent and boron with protons. More than 10% of the11C was successfully exchanged with carbon atoms in the original reagents. We also found that sublimation is useful for purifying 8-hydroxyquinoline labeled with11C. The extraction property of11C-labeled 8-hydroxyquinoline between water and chloroform could be easily monitored by radioactivity measurement.
Abstract
Activation is one of the severe problems at the high-energy accelerator facilities. By using gamma-ray spectrometry and activation detector technique, we could obtain important information on (1) nuclear reactions, (2) energy spectra of secondary particles, (3) penetration behavior of secondary particles in shield wall, (4) historical record of beam loss occurred in the accelerator rooms. It was concluded that the technique and knowledge of activation analysis are very useful to solve the radiation protection problems at the accelerator facilities.
Abstract
The11C and14C labeled fullerenes were produced by charged-particle and neutron irradiation, of C60, C70 and their mixture. It was found that a carbon atom of fullerence can be easily exchanged with a radioactive carbon atom produced by a nuclear reaction. The HPLC method was effective for identification and purification of various labeled fullerene families as chemically stable compounds. The radiochemically interesting aspect of the results is not only the production of11C and14C labeled fullerenes but also the formation of radioactive higher fullerenes which can be simultaneously produced with high yield and in carrier-free form.
Abstract
Fullerenes, C60 and C70, were irradiated by 8 and 10 MeV deuterons. The irradiated samples were dissolved in CS2 and filtered to remove insoluble by-products. Finally, radioactive fullerenes and products, such as fullerene dimers, trimers labeled with13N, were isolated and detected in the liquid phase by radiochromatography. This suggests that the energy rich13N atoms successfully incorporated into the fullerene cages and that the disrupted cages reacted with neighboring cages.
Abstract
A comprehensive study on the yields of photonuclear reactions of various types has been performed, and sensitivities and the effects of interferences in multielement photon-activation analysis have been evaluated by bremsstrahlung activation of many elements with maximum energies ranging from 30 to 60 MeV. The applicability and reliability of the method were demonstrated by analyzing standard round-robin samples and then by presenting the elemental abundances in several geological, biological and environmental materials. The method was almost insensitive to matrix effects and was assessed to be promising for nondestructive multielement determination of the materials of wide variety, giving good reproducible results for 20 or more elements.
Abstract
Highly selective and sensitive γ-ray detection was performed by coincidence and anticoincidence event analysis after list-mode data acquisition using an HPGe spectrometer equipped with NaI(Tl) and plastic scintillation detectors. In order to obtain the most suitable detection of specific nuclides, coincidence or anticoincidence spectra could be freely constructed by extracting events with particular time and energy correlations. Although the detector arrangement of this system was the same as that of a typical Compton suppression spectrometer, background counts were drastically reduced and γ-rays of particular nuclides could be selectively detected by using γ-γ, γ-X, γ-X-X, and γ-β+ coincidences.
Abstract
For decommissioning of the cyclotron and electron synchrotron facilities, the residual radioactivity in surface and core samples of concrete, collected from various parts of buildings, was determined by gamma-ray spectrometry. It was found that the concrete samples were activated mainly by neutrons and that the major radioisotopes were 152Eu, 60Co, 134Cs, 22Na and 54Mn. The maximum activity induced by thermal neutron capture was observed at the depth of 10 cm in the concrete wall near the deflector of the cyclotron. Tritium was also produced by the neutron reaction, because its concentration was proportional to the activities of 152Eu and 60Co. The surface dose rates inside the accelerator room were also monitored to define the decontamination area. The surface dose rate was proportional to the residual radioactivity, such as 60Co. A careful evaluation was very useful in order to minimize the radioactive waste during decontamination.
Abstract
A new internal standard method coupled with the standard addition method for PIXE analysis has been developed. In its basic principle, this method is characterized by that a suitable element present initially in the sample is used as an internal standard, and further the comparative standard is prepared by applying the standard addition method to the duplicated sample. When a sample contains Wa g of trace element A to be determined together with an element B which is usable as an internal standard, and when the comparative standard is prepared by adding an exactly known amount of element A, W a * g, to the duplicated sample, the absolute concentration of Wa can easily be determined by the following equation even if the above sample and comparative standard are irradiated separately by a different number of protons Wa=W a * /[(R*/R)-1] where R and R* are ratios of net photopeak counts due to the characteristic X-rays from the element A and B in the irradiated sample and comparative standard, respectively. The usefulness of the method was examined through determination of Cu, Zn, Rb and Sr in two biological materials, such as spinach and orchard leaves. As a result, this method was demonstrated to be sensitive, highly reproducible and reasonably accurate.
Abstract
Determination of carbon impurity in GaAs crystals has been investigated by photon activation analysis using the12C(
, n)11C reaction. Chemical isolation of the radiocarbon as CO2 was carried out by the combustion method using Pb3O4 as a fusing agent and/or oxidizing accelerator in a high flow rate of oxygen stream. The CO2 was then collected by passing through a double trap containing NaOH solution, and precipitated finally as BaCO3. By measuring positron annihilation gamma-rays due to the isolated radiocarbon, it was proved that determination of the above carbon impurity can be achieved easily and favourably. On the basis of the results obtained, a conversion factor for the LVM absorption of carbon at room temperature in Fourier-transform infrared spectroscopy was found to be 1.4·1016 atoms · cm–1.
Abstract
Determination of carbon in copper has been studied by photon activation analysis using 30 MeV bremsstrahlung. Chemical separation of carbon as CO2 was performed by the combustion method in a high flow rate of oxygen stream. It has been demonstrated that the trace amount of carbon in copper can be determined accurately and precisely, and that the detection limit is 0.02 
g.
