Masahisa Ito

An x‐ray spectrometer for Compton scattering

An x‐ray spectrometer has been designed and constructed for Compton scattering measurements using 40–70 keV x‐rays from an ellipsoid multipole wiggler (EMPW) installed in the accumulation ring of the National Laboratory for High Energy Physics at Tsukuba. The spectrometer has four sets of a Cauchois‐type energy analyzer and an imaging plate, which are arranged on the surface of a cone and share a scattering angle of 160°. In each energy‐analyzing system, to increase signal to noise ratio a set of vertical and horizontal slits are inserted between the analyzer and the imaging plate. A resolution of 0.13 a.u. in terms of electron momentum was achieved. A Compton profile of a vanadium single crystal was measured with an integrated counting rate of 400 counts/s.

X-ray energy dependence and uniformity of an imaging plate detector

Abstract We have obtained an imaging plate (IP) response curve as a function of X-ray energy between 4 and 58 keV. The nonuniformity of the IP response has been estimated to be about 0.5% over 10 cm × 10 cm area with uniform irradiant γ-rays.

Polarized X-Ray Absorption Spectra of Bromine-Doped Polyacetylene; Evidence for Highly-Oriented Polybromine Ions

Polarized extended X-ray absorption fine structure (EXAFS) and near-edge spectra are measured on the Br K-edge for streteh-oriented trans -(CHBr y ) x . A large difference is observed in both the EXAFS and near-edge regions between the spectra with the polarization vector E parallel and perpendicular to the axis of orientation. The Fourier transform results or polarized EXAFS demonstrate that polybromine ions are highly oriented along the fibril axis in the dopant concentration 0.015 < y < 0.036. Bromines are also shown to be covalently bonded with carbon atoms of the polymer backbone through a substitution reaction and dominate the radial distribution of bromine in the direction perpendicular to the fibril axis. Polarized near-edge spectra show that the anisotropic bonding states of bromine are characterized by the Br-Br bond in the parallel direction and the Br-C bond in the perpendicular direction to the fibril axis, respectively. We propose that trans -(CHBr y ) x can be described in terms of highly o...

Radial integrals for the magnetic form factor of 5d transition elements.

The radial integrals, j(L), where L = 0, 2, 4, for several electronic configurations in the 5d electrons of transition metal atoms and ions are calculated using radial wavefunctions from the pseudo-relativistic Hartree-Fock method in the Cowan program. The resultant values are fitted to Gaussian analytical expressions with four exponential terms, and the fitted coefficients are tabulated. This table can be used to interpret the magnetic form factor measurements for 5d transition metals.

Compton Scattering Study of Electron Momentum Density in Vanadium

The [100], [110] and [111] Compton profiles of vanadium are measured with a momentum resolution of 0.12 atomic units. The observed profiles have fine structures and directional anisotropies. Comparison of the results with the APW band theoretical predictions shows that the band theory overestimates the momentum density at low momenta and underestimates it at high momenta. The theory also overemphasizes the fine structures and the scale of the anisotropies.

Water-cooled quasi-doubly bent crystal monochromator for Compton scattering experiments

Commissioning and performance of a water‐cooled quasi doubly bent crystal monochromator for Compton scattering experiments are described. The monochromator consists of an array of twenty singly bent crystals. Each crystal is half immersed in liquid Ga‐ln alloy contained in a water‐cooled holder. This is necessary because the monochromator must be able to withstand heat load of 4 kW from synchrotron radiation from an ellipsoid multipole wiggler at the 6.5 GeV accumulation ring. The alignment procedure for twenty singly bent crystals is described in detail. Its performance is as follows; the focused beam size of 60 keV x rays is about 3 mm (vertical) and 8 mm (horizontal). The flux is 6×1012 photons/s at stored currents of 30 mA and the energy resolution is 88 eV for 60 keV x rays. Heating of various adjusting mechanisms by Compton scattered x rays from both the absorber used to suppress low energy x rays and the monochromator crystals is found to be a very serious problem for designing a high energy x‐ray ...

X-Ray Magnetic Form Factor of UTe

A measurement of the magnetic form factor of a ferromagnetic actinide compound of UTe with circularly polarized X-rays is reported. The present geometrical configuration of the measurement gives a form factor of L ( k )+0.3 S ( k ), where L ( k ) and S ( k ) are the form factors of the orbital and the spin magnetic moment, respectively. We have combined the X-ray magnetic form factor with the neutron one which gives L(k)+2S(k) (G. Busch e t a l .: J. Phys. C 12 (1979) 1391), and have deduced L ( k ) and S ( k ) separately. The obtained profiles of L ( k ) and S ( k ) show that the orbital and the spin magnetic moments are spatially spread out more than those calculated for a free uranium ion.

Structure relaxation of an amorphous Mg.70Zn.30 alloy

Abstract Structural change of amorphous Mg .70 Zn .30 alloys during isothermal annealing before crystallization was studied by TOF neutron diffraction. The difference between the radial distribution function, G(r), of an annealed sample and that of an as-quenched sample corresponds to the second derivative of G(r). This indicates that the atomic level stress relaxation by annealing induces atomic movements of 0.1 ∼ 0.3 A, which makes a phase shift in G(r). It was demonstrated that the change of short range structure by annealing in this amorphous alloy during the first stage of the relaxation before the crystallization is a process to approach the local atomic arrangement close to that in a crystalline Mg 51 Zn 20 .

Application of circularly polarized x-rays to magnetic Compton-scattering experiments

Abstract Magnetic Compton-scattering experiments are successfully applied to the measurement of the electron-spin densities of Fe and Ni metals in momentum space. Circularly polarized 60-keV X-rays emitted from an elliptical multipole wiggler installed at the 6.5-GeV storage ring of National Laboratory for High Energy Physics (KEK) were used in these experiments. The highest statistical accuracy ever achieved is obtained. The results of ferromagnetic Fe and Ni are compared with recent band-theoretical magnetic Compton profiles calculated by Kubo and Asano using the full-potential linearized augumented-plane-wave method. Contrary to previous investigations, excellent agreement is found between the experiment and the theory. This paper also gives a brief introduction of the Compton profile, following the aim of the symposium.

The magnetic Compton profile of UTe

We have performed a magnetic Compton scattering experiment with a ferromagnetic actinide compound of UTe. We have combined the results of the magnetic Compton scattering experiment and the magnetization measurement and have deduced the spin and the orbital magnetic moments. Furthermore, we have decomposed the spin moment into a 5f component and a conduction-electron-like component. We have obtained the spin moment of the 5f electron mu s(5f)=-1.21 mu B, the orbital moment of the 5f electron mu L(5f)=3.48 mu B and the spin moment of the conduction-electron-like component mu s(s,p,d)=036 mu B.