An aspheric wave-front recording system was designed to produce a holographic grating for use in a standard soft X- ray flat field spectrograph interchangeable with a mechanically ruled varied-line-spacing (VLS) grating. The grating grooves recorded with the designed aspheric wave- front recording system were processed to form a laminar groove profile by means of reactive ion etching. Measurements done with synchrotron radiation and a laboratory X-ray source are reported for this laminar-type grating and a commercial grating replicated from a mechanically ruled VLS grating that was specifically designed and fabricated for the standard soft X-ray flat- field spectrography. The laminar-type holographic grating is found to have an absolute first-order efficiency of approximately 10% for wavelengths of approximately 4.5 - 12 nm. It is also shown that the holographic grating is effective in suppressing the higher orders and stray-light level for soft X-ray of 4.36 nm (C-K) and has a comparable spectral resolution to the replica VLS grating.
Monitoring of a 720 m span suspension bridge which is located at windy and seismically active area in northern part of Japan, opened in 1998 is introduced. The purpose of the monitoring is to understand the actual dynamic behavior and loading conditions, and to develop a health monitoring scheme using ambient vibration measurement which is readily available under service conditions. Data processing scheme based on Ibrahim's time domain method is constructed for identification of natural frequencies, mode shapes and modal damping ratios. Because measurement of the input force is not available for ambient vibration measurement, statistical treatment of measured data is required to obtain reliable results. This scheme is applied to analyze the actual ambient vibration measurement of the bridge under various environmental conditions. In the analysis, amplitude dependent softening of bearing supports which is not expected at the design calculation is identified. This preliminary analysis shows that the current monitoring system is directly applicable for identification of damage at the bearing supports which is one of the hot spots for fatigue and seismic damage, and also has the potential applicability to the health monitoring of the entire bridge.
We have measured the polarization degree of the B 1s exciton emission from h-BN under resonance excitation using a multilayer rotating analyzer. We used a Mo/C 101 layers in total as a soft x-ray polarizer. The emission would include the luminescence component due to the direct recombination of the core exciton and the elastic (Rayleigh) scattering of the incident light. We have found a definite contribution of the recombination luminescence to the exciton emission peak.
In the extreme ultraviolet (EUV) region, synthetic multilayer structures are found useful as reflection polarizers. Such structures of transmission type made by removing from substrates are found useful as polarizers and phase shifters. With these multilayer polarizing elements developed, the first thin ellipsometry was performed at a photon energy of 97 eV (12.8 nm in wavelength), which demonstrated atomic sensitivity of the EUV ellipsometry.
Developments of vacuum ultraviolet (VUV) mirrors and optical elements for intense synchrotron radiation in Japan are reported. High heat load tests of chemical-vapor-deposited silicon carbide (CVD SiC) mirrors, 500 x 50 x 40 mm3, were successfully made for undulator radiation with heat flux of 0.4 W/mm2. As extensions of various CVD SiC mirrors developed at the Photon Factory, the largest CVD SiC mirror with sintered SiC substrate, 1000 x 140 x 25 mm3, and the thin CVD SiC mirror, 300 x 50 x 5 mm3, were fabricated by the SP-ring 8 project. Heat load tests of a CVD-SiC-based grating and a multilayer mirror exhibit possibilities of making high heat load optical elements in the VUV and soft x-ray (SX) regions. Measurements of optical properties of CVD SiC mirrors produced by different methods showed that the optical constants in the VUV and SX regions were almost equal to one another. A profilometer for measuring surface figures of large-size aspheric mirrors was constructed on the basis of the Twyman-Green interferometer with heterodyne phase detection method.
SiC laminar gratings have been fabricated by reactive ion-beam etching and holographic exposure. Diffraction efficiencies were measured in the region between 17 angstroms and 300 angstroms. The efficiency of the +1 order was 5 to 20% in this region with a small amount of scattered lights. An irradiation test for the SiC gratings was performed by using intense radiation with a power density of 2.7 W/mm2 emitted from a multipole wiggler installed into the 2.5 GeV Photon Factory ring. No visible damages and no reduction of the diffraction efficiencies were observed for the uncoated SiC grating after the irradiation, while a remarkable deformation of the deposited Au layer and increase of the scattered light component were observed for the grating coated with Au. In addition to these results, some experimental results of polishability of CVD-SiC are reported.
Power density distribution in multipole-wiggler radiation was measured on the beamline BL-28 of the Photon Factory using a photocalorimetric device. The beamline had no beryllium nor graphite windows, which allowed exact comparison between measured power and calculated value using Kim's formula for undulator radiation. Although the measured density was lower by an average 20% at the peak density, it was ascertained that Kim's formula gives roughly the power density of multipole-wiggler radiation. In addition, the photocalorimetry was found to be a useful means for measuring high-power x-radiation.
The effect of white wiggler radiation exposure on Mo/BN, W/BN, Mo/B4C, and W/B4C multilayers was evaluated by comparing soft x-ray reflectance at an incidence angle of 45 degree(s). All samples were prepared by magnetron sputtering onto SiC substrates. The choice of combinations was based upon annealing tests for Mo/X and W/X (X equals C, Si, BN, and B4C) multilayers, prior to any exposure tests. The Mo/BN multilayer was found to be the most stable for an exposure time of 10 min under radiation power density of approximately 2.3 W/mm2. The observed reduced reflectance for the Mo/BN and W/BN samples was found to be reducible to a radiation-induced effect on the BN layers.
A graphite foil heat absorber protecting a beryllium window from thermomechanical damage was overheated, sublimated, and became partially transparent by multipole wiggler radiation. A simple theoretical model on heating of the foil-type filter by multipole wiggler radiation was presented, confirmed experimentally, and applied to analyze the failure.
Soft-x-ray transmission multilayers have been designed and fabricated for use as polarizing elements. Polarization performance of the multilayers has been studied at a photon energy of 97 eV by rotating analyzer ellipsometry with a multilayer reflection polarizer. The transmission multilayers were found to be a good polarizer of 99.2% polarizance and a phase shifter of 90 degree(s) retardation with equal transmission ratio (5:3) and high throughput around 10%.
A laboratory reflectometer with a laser produced plasma source and a constant deviation angle monochromator is used as an ellipsometer to evaluate a transmission multilayer phase shifter. With use of the phase shifter, all normalized Stokes parameters of the incident beam to the reflectometer from the monochromator were measured.
The optical constants, (delta) equals 1 - n and k, of very thin platinum, rhodium, and gold films have been determined from the reflectance data measured in the soft x-ray region of 60 - 900 eV. Five platinum films (63 - 153 angstroms in thickness), five rhodium films (53 - 124 angstroms), and nine gold films (49 - 270 angstroms) were prepared by ion-beam sputtering on BK7 glass substrates. A Debye-Waller factor was applied to the Fresnel reflectance to take into account the reflectance degradation due to the roughness in the surface and the interface in the least-squares curve fitting analysis. The optical constants determined for the platinum and rhodium films show little dependence on the film thickness, while those of the gold films show definite dependence in a thickness range of 70 - 120 angstroms.
We have investigated the optimum deposition conditions for fabricating Mo/Si multilayers on Si wafers by means of electron-beam deposition, taking the substrate temperature and deposition rate as parameters. Mo/Si multilayers made at substrate temperatures Of room ternperature to 420°C and at deposition rates of 0.02 to 1.0 nm/s were evaluated by transmission electron micrographs of their cross sections, x-ray diffraction patterns, and their spectral reflectances for soft x rays of 10 to 17 nm. The optimum deposition parameters were found to be 100 to 150°C and 0.02 to 0.2 nm/s, respectively, for substrate temperature and deposition rate. The Mo/Si multilayer made under the optimum condition showed fairly smooth layered structure and a reflectance of ~30% for unpolarized soft x ray of 14.6 nm at an incident angle of 20 deg.
We have investigated the optimum deposition conditions for fabricating Mo/Si
multilayers on Si wafers by means of electron-beam deposition, taking the substrate
temperature and deposition rate as parameters. Mo/Si multilayers made at substrate
temperatures of room temperature to 420 °C and at deposition rates of 0.2-10 A/sec
were evaluated by transmission electron micrographs of their cross sections, x-ray
diffraction patterns, and their spectral reflectances for soft x-rays of 110-170 A.
The optimum deposition parameters were found to be 100-150 °C and 0.2-2 A/sec,
respectively, for substrate temperature and deposition rate. The Mo/Si multilayer
made under the optimum condition showed fairly smooth layered structure and a
reflectance of '3O for unpolarized soft x-ray of 146 A at an incident angle of 200.
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