Notes: Several large-size mirrors coated with a thin layer of CVD-SiC for intense synchrotron radiation have been fabricated and commissioned at the Photon Factory. Substrates of these mirrors are high-purity graphite, recrystallized SiC and sintered SiC. Detailed properties of mirror-materials are described. First test of exposure of high-power mirrors to intense radiation from the 53-pole permanent-magnet wiggler are briefly reported.

Notes: The characteristics of microchannel plates (MCPs) for detection of x rays have been investigated using synchrotron radiation in the energy ranges from 0.6 to 2.0 keV and from 5 to 20 keV. Microchannel plates are operated under the condition of an unsaturated pulse-height distribution mode. The current response curve of MCPs is measured continuously with x-ray energy variation for the first time. The experimental result of some discontinuous jumps in the response is obtained at the energies corresponding to the absorption edge of the MCP materials. In the low-energy range (hν〈2 keV), the dependence of the current response to the incident angle of x rays to the channel axis θ is measured to be proportional to cot θ, which is interpreted by the x-ray absorption near the surface of MCP channel wall. While, in the high-energy range (hν〉5 keV), a weak dependence on θ is observed, and is attributed mainly to the penetration of x rays through multiple channels.

Notes: Current response characteristics of microchannel plates (MCPs) x-ray detectors have been measured in a wide energy range from 0.6 to 82 keV using synchrotron radiation. In the current response curve with continuous photon energy, some discontinuities have been observed to correspond to absorption edges of elements which are the constituents of MCP glass and electrode materials (Si, Pb, Ba, and Fe). The dependence of the MCP response on the incident angle of x rays to the channel axis, θ, is also investigated. The characteristics change from the cot θ dependence for soft x rays (hν〈4 keV) to the sec θ one for hard x rays (hν〉60 keV). These results could provide guidelines on the design of x-ray diagnostic instruments using MCPs.

Notes: A new method for pattern reduction in the x-ray region is proposed. In its principle was used the asymmetric Bragg reflection giving the different beamwidth in the reflected beam from the incident one. Light from an undulator line (BL-2) at the Photon Factory was used to obtain highly spatially resolved replication in reasonably short exposure time. Performed was one-dimensional demagnification of a pattern with a ratio of 1/4 in the following condition: Si 111 reflection was used where the offset angle α from the surface is 22° and the wavelength λ was 3.5 λ, which is available from the 7th harmonic of the undulator radiation. The submicron scale resist pattern was resolved.

Notes: The characteristics of microchannel plates (MCPs) for detection of x rays have been investigated using synchrotron radiation in the energy range from 1.8 to 8 keV. The current response curve of MCPs is measured with approximately continuous x-ray energy variation, which is added to the previous data [T. Kondoh et al., Rev. Sci. Instrum. 59, 252 (1988)]. It is confirmed that there is a minimum in the current response at the x-ray energy of about 4 keV. The precise current response curve has been completed for the wide x-ray energy range from 0.6 to 20 keV. A transition in the incident angle dependence of current response is found from the feature based on single cylindrical photocathode model for soft x rays to that based on multiple channel activation due to the penetration of x rays through channel walls for hard x rays. In the current response of MCPs the structure similar to that in EXAFS is observed near the Si K edge.

Notes: In order to study impurity behavior on the JT-60 plasma, a spectroscopic diagnostic system, which is capable of measuring many spectra of impurity ions and their spatial distributions simultaneously, has been developed. This system consists of interchangeable unit-type spectrographs which have different lines of sight. Four types of grazing incidence spectrographs are prepared as unit-type spectrographs. These spectrographs cover the nominal wavelength regions 0.5–5, 0.5–50, 2.0–50, and 50–122 nm, respectively, and have holographic gratings with flat focal fields. Image-intensified 1024- or 512-channel photodiode arrays are used as detectors for all spectrographs. Four unit-type spectrographs are used for observing the main plasma, and two unit-type spectrographs are used for observing the plasma near the null point of the diverted discharge. One of these spectrographs has been calibrated absolutely in the wavelength region 27.5–120 nm using synchrotron radiation from the Photon Factory (National Laboratory for High Energy Physics).

Notes: 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 sophisticatedly devised aberration correction optics is commissioned.

Notes: Since undulator light is sharply collimated itself, it can be effectively monochromatized by a perfect crystal. An x-ray double-crystal monochromator with a fixed exit has been designed and built for the use of undulator light from a 60-period undulator at Photon Factory (beamline 2A). Available Bragg angle ranges from 7° to 80°. Angle scan is made by means of a goniometer outside the vacuum chamber, with the finest step of 0.1 arcsec. Magnetic fluid is used as the vacuum seal of the feedthrough. The fixed exit beam position is kept by translating the second crystal along the two mechanical guides: one for normal and the other for parallel to the crystal surface. Adjustment of the parallelity of two crystals is made manually with flexible wires. Since a total power in the central coherent portion which is limited by a 1×1-mm2 slit is not so much, a stable operation is possible without cooling the crystal. Currently, InSb (111) reflection is used. The diffracting planes of the first cyrstal is 1° off from the surface and the second is the symmetric reflection. At its fifth harmonics, brilliant undulator light of approximately 1012 photons/s mm2 with 1-eV energy resolution is available (E=2 keV).

Notes: Irradiation experiments on biological samples with monochromatic ultrasoft x-rays are inevitable in elucidating the initial process in radiobiological phenomena. However, intense light sources with continuous spectra in this wavelength region have not been available until recently. Synchrotron radiation is the best light source for the study because of its intense, continuous emission spectrum. The purpose of the project is to develop a grazing incidence ultrasoft x-ray monochromator for radiation biology studies using synchrotron radiation as a light source. The following characteristics are required in the monochromator, namely, (1) high throughput with moderate resolution; (2) wide beam area with uniform intensity; (3) little contamination of higher order lights; and (4) easy operation and maintenance. Considering the above requirements, a plane-grating type monochromator (PGM) is adopted. The monochromator consists of two premirrors (M1 and M2), a plane grating (1200 l/mm), a concave focusing mirror (r=12 m) and an exit slit. Two premirrors with different incident angles can be used interchangeably to eliminate higher order lights in the desired wavelength region. Wavelength of 30–70 A is available when M1 is used and 80–250 A when M2 is used. Expected wavelength resolution is 1% when the width of exit slit is 300 μm. All vacuum chambers accommodating these optical elements are bakable in order to attain ultrahigh vacuum. Wavelength is controlled by a microcomputer system equipped with a stepping motor and an encoder. This monochromator will be installed at beamline 12C at the Photon Factory, National Laboratory for High Energy Physics, and will be open to outside users in radiation biology by the end of 1988.

Notes: Using undulator radiation from 2 to 8 keV, quantum efficiencies [QE(E)] of gold photocathodes, microchannel plates (MCP), and silicon surface barrier (SSB) detectors have been investigated. For the gold photocathodes, the detailed structure of QE(E) near the M absorption edges has been presented. Also, the secondary electron conversion efficiency of gold has been calculated using the mass absorption coefficient given by a relativistic Hartree–Slater model and by the semiempirical values of Henke et al., respectively. Extended x-ray absorption fine structure (EXAFS) has been observed in the secondary electron current of the gold photocathode as well as in the detection current responses of an MCP and of an SSB detector. Furthermore, the new findings adding to our recent paper1 have been summarized as follows: (i) EXAFS above the Si-K edge in the MCP response depends on photon incident angles, and (ii) a little upshift of the starting point energy of EXAFS in the MCP response is observed. These detailed characteristics and their interpretation are described in the following: (i) The current responses of the MCP are obtained as a function of the incident x-ray energy for θ=13° (the bias angle of the MCP), and 40° by using a gold-monitor current. Here, θ denotes the incident angle of the photons to the channel. The data for θ=40° show a smaller jump near the Si-K edge as compared with the data for θ=13°.This is explained as follows: The incident photons for θ=13° are irradiated to and absorbed in the MCP ingredient of SiO2, while photons for θ=40° are incident to the electrode region. (The depth of the electrode coating is more than 10 μm from the MCP surface, while the photons are absorbed at less than 8 μm from the surface for θ=40°.) Thus, the data for θ=40° strongly reflect the characteristics of the electrode, but not of SiO2. The data for several values of θ consistently indicate that the height of this jump becomes smaller with increasing θ. (ii) The observed upshift of the starting point energy of EXAFS in the MCP response presents a contrast to EXAFS in the SSB detector response, in which upshift is not observed. This upshift is ascribed to the molecular structure of SiO2 (the chemical shift); that is, some valence electrons are removed from the Si atoms due to the oxidation (i.e., SiO2). Thus, the screening effects of the valence electrons on the core electron-nucleus attraction are reduced. This results in the shift of binding energy towards the higher-energy side. On the other hand, EXAFS in the SSB detector response reflects the characteristics of Si.