Haruhiko Motohashi

Synchrotron radiation beamline to study radioactive materials at the Photon factory

Abstract Design and construction of a new beamline have been described. The beamline is housed in a specially designed area controlled for radioactive materials at the Photon Factory (PF) in the National Laboratory for High Energy Physics (KEK). The beamline system consists of a front-end and two branchlines. One of the branchlines is used for X-ray photoelectron spectroscopy and radiation biology in the energy range of 1.8-6 keV and the other for X-ray diffractometry and XAFS studies as well as radiation biology in the range of 4–20 keV. The former was particularly equipped for the protection against accidental scattering of radioactive materials both inside and outside of the vacuum system.

X-ray absorption study of molten yttrium trihalides

The local structure and structural changes in molten YCl3-LiCl-KCl and molten YBr3-LiBr systems have been investigated by using a high-temperature extended X-ray absorption fine structure (EXAFS) technique. The behaviour of octahedral coordination of the halide ion (Cl(-) and Br(-)) around the Y(3+) ion has been studied by EXAFS of the Y K-absorption edge. The nearest Y(3+)-Cl(-) and Y(3+)-Br(-) distances and coordination numbers of halide ions around the Y(3+) ion do not change by mixing with the alkali halides. The stabilization of the (YCl6)(3-) and (YBr6)(3-) octahedral coordination by adding alkali halides was suggested by decreasing the Debye-Waller factor and the anharmonicity in the nearest Y(3+)-Cl(-) and Y(3+)-Br(-) interactions. The bridging structure of the (YBr6)(3-) octahedra sharing a Br(-) ion in the molten YBr3-LiBr system was studied by EXAFS of the Br K-absorption edge. The coordination number of Y(3+) around the Br(-) ion decreases from 2 in the pure melt to almost 1 in the 30mol% and 15mol% YBr3 melts. This suggests that the bridging is almost broken and the stable octahedron exists freely in the LiBr-rich melts.

Structural study of holmium (III) and uranium (VI) organic ligand complexes by extended X-ray absorbtion fine-structure spectroscopy

The structures of holmium-organophosphorus mono- and bidentate ligands and uranium-monoamide ligand complexes in solutions were determined by extended X-ray absorption fine-structure spectroscopy. The diphosphine dioxide coordinates directly to holmium with symmetric bidentate mode, while the carbamoyl phosphine oxide with asymmetric bidentate mode. The structure for uranium-N,N-dihexyl-3-ethylhexanamide complex is very similar to that for the aqua nitrato uranyl complex in bond distance and coordination number.

Study of hydrogen adsorbed on platinum by neutron inelastic scattering spectroscopy

The inelastic neutron scattering spectra of hydrogen adsorbed on platinum is reported and analyzed. (AIP)

Structural studies of lanthanide(III) complexes with oxydiacetic acid and iminodiacetic acid in aqueous solution by EXAFS

The local structure of the trivalent lanthanide (Ln(III)) complexes with oxydiacetic acid (ODA) and iminodiacetic acid (IDA) in aqueous solution was investigated by EXAFS spectroscopy. The coordination number and the bond distance were obtained by the detailed EXAFS analysis. The coordination number of Ln(III) in both the Ln-ODA and -IDA systems decreases from nine for lighter Ln(III) to eight for heavier Ln(III). The bond distances of ether O atoms from Ln(III) in the Ln(ODA)(3)3- complexes are shorter than those of N atoms in the Ln(IDA)(3)3- ones.

X-Ray Study on the Radiation Damage in LiF Crystals

The reflection intensity of x-rays was measured as a function of the distance from the irradiated outer surface to the measured location in a neutron irradiated LiF crystal; the distance was converted to thermal neutron dose. The measurements showed that the reflection intensity monotonically increased with increasing neutron dose. Rocking curves were obtained for LiF specimens, taking the irradiation conditions as parameters. The curves showed that the rocking curve broadened as irradiation proceeded, indicating that the coherent domain bocame small when neutron irradiated unless the recovery of crystalline defects actively worked. From the above results, the extinction coefficient of LiF crystal for x-rays is concluded to decrease with neutron irradiation. The decrease of extinction is suggested to be caused by the complex color centers consisting of a cluster of defects. The clustered defects and small dislocation loops, both of which are introduced by heavy neutron irradiation, also work to make the c...

Local structure of (U,Zr)Pd3 by EXAFS

Abstract Measurements of the extended X-ray absorption fine structure (EXAFS) were used to determine the local configuration around uranium and zirconium atoms in (U,Zr)Pd 3 solid solutions. Interatomic distances and lattice constants from EXAFS and X-ray diffraction, respectively, are discussed in relation to the effect of addition of ZrPd 3 to UPd 3 . The decrease in U–Pd distance with ZrPd 3 addition was appreciably smaller than the average M–Pd (M=U, Zr) distance of the solutions. The result suggests that the 5-f localized electronic structure of UPd 3 resists compression by the addition of ZrPd 3 .

Choice of Collimators for Neutron Diffraction

The effect of the collimators on Bragg peaks was investigated experimentally, in order to obtain a high intensity and good resolution for neutron diffraction measurements of a powder sample The results snow that, in rather small scattering angle, the angular divergence of the second collimator must be larger than that of the first and the third collimator, because the focussing effect makes the second collimator insensitive to a width of diffracted neutrons.