Takeshi Namioka

In situ ellipsometric study of optical properties of ultrathin films

A method has been developed for analysis of a series of ellipsometric data taken in situ during deposition. With this method the optical constants n and k and thickness d of growing ion-beam-sputtered films of C, Si, Ni, Nb, Mo, Ru, Rh, Pd, Ag, W, Re, and Au have been determined as a function of deposition time t. The minimum critical thickness d(i) needed for a film to become optically isotropic has been determined from the n, k, d-versus-t curves. Anomalous behavior of these curves appears in the region d less, similar d(c) resulting from a breakdown of the isotropic film model employed. This is shown, by transmission electron micrographs, to have a correlation with a transition region from island/anisotropic to continuous/isotropic.

Layer-by-layer design method for soft-x-ray multilayers

A new design method effective for a nontransparent system has been developed for soft-x-ray multilayers with the aid of graphic representation of the complex amplitude reflectance in a Gaussian plane. The method provides an effective means of attaining the absolute maximum reflectance on a layer-by-layer basis and also gives clear insight into the evolution of the amplitude reflectance on a multilayer as it builds up. An optical criterion is derived for the selection of a proper pair of materials needed for designing a high-reflectance multilayer. Some examples are given to illustrate the usefulness of this design method.

High-resolution VUV spectroscopic facility at the Photon Factory

A high-resolution spectroscopic facility, consisting of a 6.65-m vertical dispersion off-plane Eagle spectrograph/monochromator and a unique predisperser system of zero-dispersion type, has been designed and constructed at the Photon Factory. A description is given of design principle, optical system, mechanical arrangement, vacuum system, control system, and performance in the spectrograph mode. The resolving power was estimated from the separation between two closely lying lines of Ar I at ∼79 nm in the seventh order to be >2.5 × 105 —the highest resolving power ever demonstrated for this spectral region.

Performance of a wideband multilayer polarizer for soft x rays

Performance of a Ru/C multilayer polarizer of double‐crystal x‐ray monochromator type has been evaluated in the soft x‐ray region using synchrotron radiation. The throughput efficiencies for s‐polarized light were found to be 11.5% at 100 eV and higher than 4% over an energy range of 80–150 eV without higher‐order contamination. Its polarizance was higher than 99.0% at 88 eV and more than 94% over a range of 80–110 eV.

A 10 m grazing incidence monochromator for high resolution soft X-ray spectroscopy at the photon factory

Abstract A description of a novel 10 m grazing incidence monochromator is given on the optical and the mechanical design features as well as on its performance achieved. The monochromator was designed and constructed at the Photon Factory for high resolution spectroscopic studies in the soft X-ray region.

A New Constant Deviation Monochromator for Angle Resolved Photoemission Spectroscopy

A new type of constant deviation monochromator equipped with three interchangeable concave gratings (600, 1200 and 2400 grooves/mm) of 2 m radius of curvature was designed and built specifically for angle resolved photoemission spectroscopy at photon energies ranging from 20 to 160 eV. The exit slit of the monochromator is at a fixed position, whereas the entrance slit moves, simultaneously with grating rotation, along the direction of the incident light so as to minimize the amount of defocusing. A monochromatic light spot of 0.5 mm in diamter was obtained at the fixed sample position with the aid of a toroidal postfocussing mirror. It is found over the energy range concerned that the resolution is bettern than 1700 with 25 µm slits, and the photon flux obtained behind the toroidal mirror for a horizontal acceptance angle 0.5 mrad is 4×1010 photons/s when the width of the slits is 50 µm and the stored current for synchrotron radiation is 100 mA.

Design studies of mirror-grating systems for use with an electron storage ring source at the photon factory

Abstract The design method developed during the course of designing several grating instruments for use with a 2.5-GeV electron storage ring at the Photon Factory of the National Laboratory for High Energy Physics is described. The method is shown to be quite effective in designing complete optical trains which are tailored to maximize throughputs and resolution and to minimize aberrations, interference by unwanted wavelenghts and/or specific site-imposed constraints over limited wavelength ranges. The results obtained with this design method are given for the cases of 6.65-m off-plane Eagle type spectrograph/monochromator under construction and a planned 10-m grazing incidence monochromator.

Soft X-ray reflectometer with a laser-produced plasma source

A soft X-ray reflectometer with a laser-produced plasma source driven by a Q-switched Nd: YAG laser or a XeCl excimer laser was constructed. By comparing the reflectances of a multilayer mirror with the data obtained using synchrotron radiation, its usefulness for reflectance measurements in the soft X-ray region (40-130 eV) is demonstrated.

Full polarization measurement of synchrotron radiation with use of soft x-ray multilayers

Using two Ru/Si multilayers as a phase shifter and an analyzer, we have measured the state of polarization for 12.8‐nm synchrotron radiation (SR) of the beam line 11A at the Photon Factory. It has been found that the state of polarization depends largely on the vertical inclination angle of the first mirror of the beam line. From the phase information, we have determined parameters of the polarization ellipse including handedness.

Performance of the 6VOPE high resolution VUV spectroscopic facility in the photoelectric detection mode

Absorption measurements of krypton gas have been carried out to evaluate the performance of the high resolution spectroscopic facility 6VOPE using photoelectric detection. The 6VOPE is designed to make use of high spectral orders and consists of a 6.65-m vertical dispersion off-plane Eagle spectrograph/monochromator and a zero-dispersion tandem grating predisperser system. Focal plane scanning is used to achieve high resolving power (>==10(5)) for photoelectric measurements in the 40-200-nm range. A description is given of the mechanism and performance of the 6VOPE in the focal plane scanning mode. The resolving power and focused stray light level at ~88 nm are estimated experimentally to be greater, similar1.5 x 10(5) and less, similar 3%, respectively. Contrary to the usual experience the focused stray light of the 6VOPE is composed entirely of VUV light scattered from the main grating.