Akira Mikuni

Electrical and optical properties of black phosphorus single crystals

Abstract Large single crystals of black phosphorus have been prepared by a large volume-high pressure technique at high temperature. Using the crystals, we have measured temperature dependences of the electrical conductivity and the Hall coefficient, the FIR cyclotron resonance absorption and the reflectance for synchrotron radiation. All samples obtained are p-type and the Hall mobility reaches 5×10 4 cm 2 v·sec around 20K. The anisotropies of the effective mass, the Hall mobility and the SOR reflectance along the three crystal directions, a, b, and c, have been observed.

Investigation of carbon contamination of synchrotron radiation mirrors

Abstract Carbon-contaminated synchrotron radiation mirrors have been successfully cleaned by a dc glow discharge in oxygen. Reflectance and angle-resolved scattering have been measured before and after cleaning. The effect of carbon contamination on reflectance is severe at near normal incidence whereas it is small at grazing incidence. The decrease in reflectance is most noticeable for photons with an energy below about 10 eV. In the discharge arrangement in which the mirror surface did not face an electrode, the reflectance of contaminated mirrors was nearly restored to that of uncontaminated mirrors and the scattering level was reduced. An additional discharge, in which the mirror surface faced the electrode, degraded the reflectance but produced no appreciable change in the scattering level.

Vertically and horizontally focusing beam line BL‐3A of the Photon Factory

An x‐ray beam line BL‐3A at the Photon Factory has been designed and constructed to have optical components of a collimating paraboloidal mirror, a sagittal‐focusing double‐crystal monochromator, and a focusing paraboloidal mirror. The evaluation at the (+,−,−) setting of Si (111) showed that the vertical angular divergence was reduced from 13.4 to 9.5 (arcsec) by the collimating mirror. The vertical focusing with two mirrors gave the beam size of 0.2 mm (1/50). The horizontal beam size was reduced to 1/60 by sagittal focusing.

Design and construction of beamline‐NE1 for circularly polarized synchrotron radiation from the 6‐GeV TRISTAN Accumulation Ring

The beamline for the circularly polarized synchrotron radiation at the 6‐GeV Accumulation Ring for the TRISTAN project is now under construction. The insertion device of this beamline was designed to produce circularly polarized x rays at the photon energy range of 200 eV∼100 keV. The beamline is divided into the following three branches: (1) High resolution Compton scattering and magnetic Compton scattering experiments; (2) multipurpose experiments such as magnetic x‐ray scattering and magnetic x‐ray absorption; and (3) completely circularly polarized soft x rays.

High pressure–high temperature research using high energy synchrotron radiation at the TRISTAN accumulation ring (invited)

High energy synchrotron radiation emitted from the bending magnet of the TRISTAN accumulation ring (6.5 GeV) at the National Laboratory for High Energy Physics has been used for the high pressure–high temperature diffraction experiments using a multianvil press system, MAX80. Owing to the specific features of high energy synchroton radiation, significant improvements have been brought to the high pressure research. The wide energy range of diffraction spectrum leads to an increase in the number of observable diffraction peaks in an energy‐dispersive method, resulting in an increase in the accuracy of the measurements of the lattice and thermal parameters. Due to the high penetrating power of radiation, diffraction patterns can be taken in a short time from materials containing heavy elements or materials surrounded by a metal foil. Typical examples of high pressure–high temperature experiments with high energy synchrotron radiation are also described.

Mechanically ruled diffraction gratings for synchrotron radiation

Abstract Improvements in the ruling, replication, and measurement of mechanically ruled diffraction gratings, are described, especially for synchrotron radiation applications. Profiles of extremely fine and shallow grooves are measured with a scanning electron microscope. Replica gratings can now be baked for high vacuum applications using a high-temperature durable epoxy as cement. The groove space variation technology is effective for reducing aberrations in concave grating monochromators. A grazing incidence monochromator without using collimating and focusing mirrors has been designed and fabricated for a soft X-ray beamline at the Photon Factory by utilizing the advantage of a varied-space plane grating with self-focusing properties.

Observation of Undulator Radiation. : I. Operation Studies and Visual Observation

A 19-pole permanent magnet undulator has been tested by inserting it into a straight section from outside the vacuum chamber of the SOR-RING, a dedicated synchrotron radiation source operated between 0.2 and 0.38 GeV. It was confirmed that the undulator field did not seriously disturb stable operation by observing the shift of the closed orbit and the shift of the betatron numbers. Some results of visual observation of the radiation are presented. The polarization character was studied on the rainbow circle with a polarizer and some theoretical results by Kitamura were confirmed. It was found that the interfering synchrotron radiations along the straight section of the storage ring make a series of rainbows even without the undulator field.

Ultraviolet/ozone cleaning of a soft x-ray grating contaminated by synchrotron radiation.

A grating which was carbon contaminated by synchrotron radiation was cleaned using UV/ozone asher, and soft x-ray reflectivity was recovered into the original level after cleaning.

Equilibrium phase instability in the double RF system for Landau damping

Abstract A longitudinal coupled bunch instability in an electron storage ring was suppressed by the Landau damping in a double rf system composed of a second harmonic rf cavity. The damping became ineffective, however, above a beam current of 30 mA; the beam bunch slipped out of the optimum phase of the total rf voltage for the damping, which accompanied a simultaneous deformation of the total voltage. The unexpected phenomenon of the phase slip is explained by the concept of equilibrium phase instability of the beam bunch based on a rigid bunch model. The phase slip of the bunch was suppressed by introducing a phase feedback loop, resulting in an improvement of the maximum beam current for the damping. Discussions are made on various conditions of the equilibrium phase instability, including another possibility for avoiding the phase slip.

New multipole wiggler/undulator beamline (BL‐16) at the Photon Factory

Design and experience of the initial operation of a new beamline (BL‐16) for a 3.6‐m‐long, 53‐pole wiggler/undulator constructed at the Photon Factory are described. The insertion device has hybrid permanent magnets with a period of 12 cm and a maximum magnetic field of 1.47 T. In the undulator mode, the energy of the fundamental peak can be varied from 40 to 400 eV. In the wiggler mode, an x‐ray beam (critical energy of 6 keV) 50–100 times more intense than that from the bending magnets is obtained. The beamline consists of two time‐shared branch lines: a side beamline for soft x‐rays in the undulator operation, to which photon beams are deflected sideways by a cylindrical SiC mirror, and a straight line for hard x rays under the wiggler operation. On the hard x‐ray line, a fixed‐exit sagittal‐focusing double‐crystal monochromator has been installed and commissioned. Collimating and refocusing mirrors will be installed in 1989. On the undulator beamline, a soft x‐ray monochromator utilizing sophisticated...