Yasushi Kagoshima

Strong Circular Dichroism in Photoelectron Diffraction from Nonchiral, Nonmagnetic Material–Direct Observation of Rotational Motion of Electrons

Strong circular dichroism is found in 2-dimensional angular distribution patterns of the Si 2p photoelectrons from the Si(001) surface, which has no chirality and magnetism. The forward focusing peaks in the pattern rotate clockwise or counterclockwise when the helicity of the incident circularly polarized light is reversed. These rotations of the pattern are explained by rotational motion of photoelectrons around the nuclei. This is the first direct observation of the rotational motion of the electrons and clarifies the correspondence between the classical and the quantum mechanical ideas of angular momentum.

Hyogo beamline at SPring-8: multiple station beamline with the TROIKA concept

Abstract The Hyogo beamline has been constructed as the first contract beamline at SPring-8. It has three experimental hutches and their corresponding three monochromators. Two upstream transparent monochromators enable us to perform three experiments for different purposes simultaneously. Employing a figure-8 undulator, horizontally or vertically polarized X-rays can be obtained in a wide energy range. Rocking curves of the monochromators were almost identical to theoretical ones.

PHASE-CONTRAST X-RAY IMAGING USING BOTH VERTICALLY AND HORIZONTALLY EXPANDED SYNCHROTRON RADIATION X-RAYS WITH ASYMMETRIC BRAGG REFLECTION

Results of phase-contrast X-ray imaging are presented. The optical system employed consisted of a successive arrangement of horizontal and vertical (+, -) double crystals taking asymmetric Bragg reflection with an asymmetry factor of ~0.2. The original beam size was thus expanded in both directions and the field of view actually obtained was ~5×5 mm2. Boundary structures in samples were clearly observed with much higher contrast than those obtained in conventional absorption-contrast imaging. Since this method works in real time, it will provide a new X-ray imaging diagnosis technique for in situ observation over a large area of the samples.

Trace elemental analysis of drugs of abuse using synchrotron radiation total reflection X-ray fluorescence analysis (SR-TXRF).

Synchrotron radiation total reflection X-ray fluorescence spectroscopy (SR-TXRF) was utilized to analyze various trace elements in small amounts of drugs of abuse. Sample amounts of 1 microL solutions containing 10 microg of drugs (methamphetamine, amphetamine, 3,4-methylenedioxymethamphetamine, cocaine, and heroin) were spotted on silicon wafers for direct analysis. In addition, a leaflet of marijuana was set directly on a silicon wafer, and opium in the form of a soft lump was smeared on another silicon wafer for analysis. In these experiments, about 10 pg of contaminant elements could be detected. For example, in a seized methamphetamine sample, iodine was found, which could be indicative of synthetic route. In seized 3,4-methylenedioxymethamphetamine samples, variable amounts of phosphorus, calcium, sulfur, and potassium were found, which could not be detected in a control 3,4-methylenedioxymethamphetamine sample. For marijuana and opium, two spectral patterns were obtained that were far different from each other and could be easily discriminated. Using SR-TXRF, pg amounts of each trace element in 10 microg of various drugs can be easily detected, which is not the case either for a standard TXRF experimental system or for other elemental analysis techniques.

Circular multilayer zone plate for high-energy x-ray nano-imaging

A circular multilayer zone plate (MZP) was fabricated and its focusing performance was evaluated using 20-keV x-rays. MoSi(2) and Si layers were alternately deposited by DC magnetron sputtering on a wire core; all the interfaces satisfied the Fresnel zone condition. The measured line spread function was converted to a point spread function by tomographic reconstruction. The results suggest that the MZP has the potential to realize the diffraction-limited resolving power, which is calculated to be 35 nm using the diffraction integral. Furthermore, scanning transmission microscopy using the MZP could resolve a 50-nm line-and-space pattern.

Optical Properties of MoSi2/Si Multilayer Laue Lens as Nanometer X-ray Focusing Device

In this study, we designed and fabricated a multilayer Laue lens (MLL) as a hard X-ray focusing device. MoSi2 and Si were chosen to form the layers by DC magnetron sputtering owing to their superior properties. The optical properties of the MLL were measured at BL24XU of SPring-8 for 20-keV X-rays. In order to confirm the effect of dynamical diffraction, far-field diffraction images were captured at various incidence angles and depths. The resultant intensity distributions showed a similar structure to those derived through calculations. An almost diffraction-limited size of 28.2 nm was obtained. The maximum local diffraction efficiency was 64.7%.

10 keV X-Ray Phase-Contrast Microscopy for Observing Transparent Specimens

Hard X-ray phase-contrast microscopy has been performed with phase plates of tantalum using an X-ray beam from an undulator in SPring-8. The photon energy was set at 10 keV near the L3 absorption edge of tantalum (9.9 keV) in order to increase the phase contrast. To demonstrate its capability, a transparent specimen was imaged clearly in the reverse contrast with phase plates to shift the phase by one-quarter and three-quarters of a period, while conventional absorption imaging showed little contrast. Further, an image contrast as high as approximately 40% can be obtained for the cell walls of another specimen.

Construction and performance of BL28 of the Photon Factory for circularly polarized synchrotron radiation

A branch beamline, BL28A, has been constructed for the application of circularly polarized vacuum ultraviolet radiation. The radiation can be obtained in the helical undulator operation mode of an insertion device, EMPW♯28, which is also cut for elliptically polarized hard x‐ray radiation. T first harmonic of the helical undulator radiation can be tuned from 40 to 350 eV with its corresponding K value from 3 to 0.2. A monochromator working basically with constant deviation optics was installed, and has started its operation. A circularly polarized flux of ∼1010 photons/s has been achieved with energy resolution of around 500–1000 at the first harmonic peak. The circular polarization after the monochromator was estimated to be higher than 70% by comparing theory and experiment on the magnetic circular dichroism of nickel films in the 3p‐3d excitation region. The design philosophy of the beamline and recent results on the performance tests are presented.

Measurement of the coherence of synchrotron radiation

The first-order spatial (transverse) coherence of synchrotron radiation has been measured using a Youngs interferometer at BL28A (a helical-undulator beamline) of the Photon Factory, KEK. The range of the photon energy is about 70-180 eV. The visibility of the fringe was found to depend largely on the electron emittance and the intrinsic photon emittance. In principle, it is possible to gain knowledge of the very small electron emittance, of the order of 10(-10) m rad, without disturbing the electron beam in the storage ring.

X-ray phase-contrast imaging with submicron resolution by using extremely asymmetric Bragg diffractions

We have obtained x-ray phase-contrast images with high spatial resolution by using extremely asymmetric Si 111 Bragg diffractions near the critical angle of the total reflection. The x-rayimage could be magnified to 294 times in both vertical and horizontal directions. By using this x-ray microscopy system, we have observed clear phase-contrast images of a 0.7-μm-wide gold-line pattern.