Search

Proton beam writing (PBW) is one of the direct write techniques for the purpose of deep micromachining. Together with the flexibility of the direct write feature, micromachining of high-aspect-ratio structures is possible due to the straight trajectory of the MeV energy protons. However, direct writing is a low throughput process, when compared with a mask process such as UV lithography. For better productivity, coupled use of PBW with electroplating has been proposed as a method to fabricate metal microstructures for molds of imprint lithography. We demonstrate the electroplating of high-aspect-ratio Ni microstructures on PMMA micromachined by PBW.

Electrical resistivity and Hall coefficients of layered chalcogenides of TlCu 2-x Se 2 , TlCu 2-x Te 2 and (Tl 1-x Ba x )Cu 2 Se 2 were measured on sintered pellets. TlCu 2-x Se 2 and TlCu 2-x Te 2 were stable in the range of (2-x) between 1.95 and 2.00, and 1.96 and 2.00, respectively. TlCu 2 Se 2 gave fairly small values of p at low temperatures (e.g., p = 2 x 10 -7 Ωcm at 2 K). TlCu 2 Te 2 gave a p of ca. 3 × 10 -6 Ωcm at 2 K. The values of residual resistivity were also quite small for these compounds in spite of the presence of a large number of impurities and lattice defects. TlCu 2-x Se 2 showed T 2 dependence of p below 50 K, indicative of electron-electron scattering. Hall measurements for all systems showed that conduction occurs predominantly by holes originating from charge compensation, and by a small number of electrons. The Hall mobility showed substantial T -3/2 dependence for all samples, suggesting the dominance of acoustic phonon scattering. The (Tl 1-x Ba x )Cu 2 Se 2 system showed mixed conduction with holes and electrons, where electrons originate from the Ba 2+ ions that are substituted for Tl + ions.

In Japan Atomic Energy Research Institute (JAERI), successful development and operations of the High Temperature Engineering Test Reactor (HTTR) are coordinated by programs to study applied systems of the promising reactor technology. One such program being carried out from 2001 to 2007 is the design and development for the Gas Turbine High Temperature Reactor of 300 MWe nominal capacity (GTHTR300), aiming at demonstration of a prototype plant in 2010s in Japan. GTHTR300 features an original design of fuel cycle based on improved HTTR fuel element and of greatly simplified plant system in pursuit of economical performance with minimal development requirements. The fuel cycle characterizes on high burnup, low power peaking factor, and extended refueling interval. The plant system incorporates salient design simplification including conventional steel reactor pressure vessel, non-intercooled power conversion cycle, horizontal single-shaft turbomachine, and distributed modular maintenance of the overall plant. Planned research and development supporting detailed design efforts include performance tests of subscale components and control system. This paper describes the GTHTR300 reference design and related R&D activities in JAERI.

The electron-density distributions of two approximants, metallic Al 12 Re constructed of 13 atoms icosahedra with the center Re atoms and non-metallic α-Al–Mn–Si constructed of 12 atoms icosahedra without the center atom, are obtained using the maximum entropy method with synchrotron radiation powder data. Since the minimum electron-density of Al 12 Re is about one hundred times larger than that of α-Al–Mn–Si, Al 12 Re has free electron background and apparently metallic bonding. α-Al–Mn–Si is found to have strong covalent bonds in the Mackay icosahedron and those between the glue atom sites and the Mackay icosahedron. The covalency of Al (or Si) icosahedron and that between Al (or Si) and Mn atoms are considered to be the origin of the pseudogap in the α-Al–Mn–Si rather than the Hume–Rothery mechanism.

When the magnetic characteristic of amorphous magnetic materials is measured by an SST, the induced voltages of the H-coil are small compared to the noise. In order to decrease the noise effect on the power loss measurement, hundreds of averaging of the measured values are effective. As the induced voltages are input to a computer through A/D converters, usually the instantaneous values of these data are averaged, and finally the power loss is calculated. Another averaging method is compared with the method mentioned above. The power loss is calculated at every measurement, and hundreds of measured power losses are averaged. When a transmission method of A/D converter is added, the second method is superior to the first method.

No-load losses P of transformers core have been considerably decreased through introduction of the so-called multi-step-lap designs. However, profound guidelines for the optimum step-number N do not exist. This study shows that the combination of both N and working induction B characterises the flux distribution. Transformer cores can operate in an over or an under-critical way depending on N and B.

In order to clarify the difference between the magnetizing current method and the H-coil method quantitatively, a special single-sheet tester which can separate the iron loss produced in the yokes is designed. The results measured show that 1.7–3.9% of power loss difference in the two methods is mainly due to the iron loss in the yokes.

We have studied heat-treated (950–1300°C) 6H–SiC(0001)Si and (0001)C face with photoemission spectroscopy using synchrotron radiation (SR-PES) and low energy electron diffraction (LEED). We observed LEED patterns of SiC 1×1, 3 × 3 , 3 × 3 +6 3 ×6 3 and graphite 1×1 sequentially with increasing heating temperature for (0001)Si face and SiC 1×1 for (0001)C face, respectively. We have measured Si(2p) spectra and valence band energy distribution curves (VB-EDCs). The trend of sublimation of Si atoms from surface is different between Si- and C-face. 3 × 3 superstructure must be Si-derived. The 6 3 ×6 3 structure could be explained as a moire pattern caused by monolayer-graphite sitting on SiC surface. Si 3s-derived state of SiC 1×1 is different between SiC 1×1 for Si- and C-face. It is suggested that a single crystal graphite layer grows on Si-face and a polycrystalline graphite is formed on C-face for heated specimens above 1150°C.

On the commercial stage of FBR, the improvement of the fuel handling system which directly removes spent fuels from the reactor without in-vessel storage, will be useful to enhance an effective utilization of nuclear resources. Minor actinides (MA) loading measures such as the heterogeneous loading (two kinds of MA contents-fuel assemblies are loaded to the same reactor) and the homogeneous loading were extracted, and their suitability for the commercial FBR was estimated from standpoints of the fuel handling system cost and the contribution to the smooth fuel recycle flow. And it was clarified that the heterogeneous MA loading was useful for the transition period from LWRs to FBRs due to the promotion for the Pu utilization and the MA transmutation, and the homogeneous MA loading for the period of only FBRs due to the reduction for the TRU (Pu and MA) inventory outside the reactor.

In this paper we obtain a linear model from the frequency response of a piezoelectric scanner which is widely employed in scanning probe microscopy. A model quality evaluation method based on robust identification techniques is used to choose the best low order model. It is seen that the obtained model accurately predicts the behavior of the piezoelectric scanner in the desired range of deformations.

Initial process of Co 6HSiC (0001) contact has been intended to study using Auger electron spectroscopy (AES) and scanning tunneling microscopy (STM). Considering that 6HSiC(0001) has a polar surface i.e. Si or C terminated face, we first tried to study Co deposition on either Si(111)7 × 7 or a carbon film. Co silicide like CoSi2 starts to be formed when Co is deposited on a clean Si surface. AES and extended electron energy loss fine structure (EELFS) studies have clarified the fact that Co atoms form clusters when they are deposited on carbon films prepared on Si substrates, where Co clusters are found to be unreactive with a carbon film. Further it is suggested that the bond length between CoCo nearest neighbors shrinks for small cluster i.e. at the initial stage of the Co adsorption. Co atoms adsorbed on 6HSiC(001)6 × 6 reconstructed surface are likely to form clusters, which is the case for other reconstructed surfaces.

We have investigated 4H- and 6HSiC(0001)Si faces prepared by heat treatment using Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) in ultra high vacuum (UHV). The following were elucidated: 3 × 3 reconstruction was observed on the surface prepared at ∼ 1000°C, while 6 × 6 superstructure was observed for a specimen prepared at ∼ 1200°C. The 6 × 6 reconstruction can be explained as a moire pattern produced by a graphite layer sitting on top of SiC surface. Also AES p-p height ration of Si(LVV) C(KLL) decreased at a higher temperature for 4HSiC than for 6HSiC, which could be due to the fact that the bond strength of 4HSiC is more than that of 6HSiC.

We have investigated heat-treated 4H- and 6H-SiC(001)Si surfaces using AES, LEED, EELS and STM in ultra high vacuum (UHV). √3 × √3 and 6 × 6 reconstructions were observed in the STM study at ∼1000 and ∼1200°C, respectively. On the other hand, 6√3 × 6√3 superstructure was observed by LEED at ∼1200°C. The AES p-p height ratio of Si ( LVV ) C ( KLL ) decreased at higher temperatures. EELS proved the existence of a graphite layer on top of the specimen surface. Considering these experimental results, the 6 × 6 reconstruction observed by STM can be explained as a moire pattern produced by a graphite layer sitting on top of the SiC surface.

A Japanese intercomparison of measurements of the magnetic properties of amorphous ribbons was carried out. Although the results for power loss are in fairly good agreement, the results for peak magnetic field strength and apparent power differ considerably.

This paper presents a preliminary study on nuclear characteristics of plutoniumburning with High Temperature Gas-Cooled Reactor (HTR). The following information is obtained from comparison of features of HTR and cell burn-up calculations with the use of HTR fuel: (1) HTR has good potential for plutonium utilization. (2) Core property changes at around the same quantity of plutonium as fissile uranium. (3) In the case of small size HTR, plutonium loading of 0.5% in fuel volume is feasible without any serious influence on basic characteristics. Plutonium loading of 0.1% causes no problems, and improves burn-up characteristics. (4) The quality of plutonium becomes poor in the discharged fuel.

In order to analyze the flux distributions in anisotropic materials, the magnetic characteristics along arbitrary directions, which are quite different from those along the rolling and transverse directions, should be taken into account. This paper reviews the recent progress in measuring magnetic characteristics and computational techniques for evaluating the flux distribution in anisotropic materials.

A three dimensional numerical simulation model for snowdrift is suggested. The simulation results showed a good agreement with the observation.

In this study, ZnS thin films prepared by low pressure metalorganic chemical vapor deposition (MOCVD) have been deposited on HOYA NA-40 glass coated with indium tin oxide (ITO). The effects of the [H 2 S]/[DMZn] molar ratio on the crystallinity and surface morphology of epitaxial ZnS thin films have been studied. The surface morphology, which has been evaluated by scanning electron microscope (SEM), shows a relatively flat and uniform surface. The crystallinity has also been measured. We have also etched the ZnS thin film by reactive ion etching (RIE) in a mixed gas of Cl 2 , BCl 3 and Ar.

TiN films with a thickness of about 1.0 μm were formed on Si(111) using the dynamic ion beam mixing method at an acceleration voltage of 2–30 kV nitrogen ion current densities of 0.4–5 A/m 2 , and Ti evaporation rate of about 0.7 nm/s. The Vickers hardness of these films showed high values of 2300–3300 kg/mm 2 . Film characterizations were performed using the XRD, TEM, AEM and SIMS methods. An amorphous layer and a polycrystalline TiN layer were sequentially formed on Si substrates. Si, N and Ti atoms were detected in the amorphous layer. Ti in the amorphous layer was thought to be mainly knocked on by N + and N 2 + ions. At 2 and 5 keV nitrogen energy, the thickness of the amorphous layers was 5 and 12 nm, respectively, which corresponds closely with the projected range of N + ions. No clear boundary or void could be observed in the TiN layer.

It is difficult to achieve sufficient accuracy of power loss measurement at high magnetic field densities where the magnetic field strength gets more and more distorted, or in cases where the influence of noise increases (small specimen cross section). The influence of averaging on the accuracy of power loss measurement was studied on the cast amorphous magnetic material Metglas 2605-TCA. The results show that the accuracy of power loss measurements can be improved by using the averaging of data acquisition points.

A three-dimensional. numerical simulation for snowdrift is suggested. Saltation as well as suspension are taken into consideration in this model. The procedure is as follows: (1) Air flow field is simulated solving the Reynolds equations and the continuity equation. (2) Using the result of the air field flow simulation, the blown snow density field is simulated solving the diffusion equations in which the fall velocity of blown snow particles is considered. In the boundary conditions, saltation is taken into consideration. (3) Finally, the snowdrift rate is computed as the amount of snow particles which are not blown by saltation. This model is tested for three cases: snow fences, a wind scoop, and snowdrift around a hill. The computed results showed a good agreement with the observations.

Norepinephrine(NE) release in posterior nucleus(PH) of the hypothalamus was examined before and during acute shaker (oscillation) stress in sinoaortic denervated(SAD) and sham-operated(SO) rats. NE in PH extracellular fluid of freely moving rats was collected by microdialysis and measured by sensitive radioenzymatic assay. Three days after SAD or SO operation, mean arterial pressure(MAP) and heart rate(HR) were significantly higher in SAD rats than SO rats. Baseline levels of NE in PH dialysate were also significantly elevated in SAD rats. Although five minutes of shaker stress elicited pressor and tachycardic responses coupled with increased NE release in PH of both groups, the increases in MAP and dialysate NE were larger in SAD than SO rats. These findings indicate that noradrenergic neurons in the PH respond to stress-induced stimuli and receive tonic input from baroreflex pathways.

The surface structure of 6H−SiC(0001)Si prepared by heat treatment has been studied using Auger electron spectroscopy (AES) and scanning tunnelling microscopy in ultra-high vacuum (UHV-STM). The C(KLL) Auger signal increased in comparison with Si(LVV) for increasing heating temperature. 6 × 6, 3 × 3 and √3 × √3 reconstructions were observed above 1100°C by STM, but only 6 × 6 domains exist at the highest temperature (1250°C). The 6 × 6 and 3 × 3 reconstructions can be explained by the structure of a graphitic layer on the SiC surface and by the 3 × 3 DAS model, respectively.

The effects of geomagnetism and residual magnetism in various types of single sheet testers (SST) on magnetic characteristics, such as the power loss of amorphous magnetic material, have been investigated. It has been clarified that the measured accuracy is affected significantly by the directions of the yoke. The single-yoke types show unfavorable performance when used outside a magnetic shielding room (MSR). If the yoke is not demagnetized, the horizontal double-yoke type requires a MSR. However, the performance of the vertical double-yoke type is acceptable even in the case without a MSR.

In the horizontal single sheet tester (SST), the effects of the specimen and yoke dimensions, of the yoke type and of the overhang on the measurement of iron losses are examined. It is shown that the error affecting the measurement of iron losses using the conventional horizontal-type SST is significantly dependent on specimen width and overhang.

We have focused on the fundamental effect of Al implantation on 6H–SiC. Aluminum ions were implanted at 330 keV into 6H–SiC substrates at room temperature. Implanted samples were annealed in a temperature range from 1000 to 1500°C in an SiC crucible with an argon atmosphere using rf heating. The implanted samples were evaluated by several means such as optical transmission, SIMS, Raman, and RBS spectroscopy together with electrical measurements. The optical transmission of the sample at a wavelength of 500 nm before and after ion implantation (ion dose: 2 × 10 15 cm −2 ) were 65 and 3% respectively, where a substrate thickness of 300 μm was used. After annealing at 1000°C for 40 min, the transmittance recovered up to 33%. By RBS measurement, the implanted damage still remained after annealing at 1500°C for 40 min. Sheet resistance was also measured at various annealing temperatures.

The magnetic characteristics of magnetic materials very low temperature have been measured. The power loss of amorphous metal at very low temperature is less than a quarter of that of grain-oriented silicon steel. It is shown that a new type of superconducting amorphous core transformer, which is immersed in liquid helium, is lihgter, smaller and more efficient than the conventional normal conducting transformer.

When the magnetization curve (BH) is measured in a ring specimen, the curve obtained has an intrinsic error source, because the mean magnetic path length is assumed to be equal to the mean geometric path length. In this paper, a method is proposed for estimating the true BH curve by means of numerical calculations. This newly developed method enables us to eliminate the error in setting the mean magnetic path length.