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SrGa2S4:Eu and CaS:Eu phosphors are useful to provide a wider color gamut to LCDs since their emissions are narrower, but they easily react with moisture. The phosphor sheet containing them was developed. The moisture barrier layers on it can separate them from a humid atmosphere. The LCD with the phosphor sheet could realize the wider color gamut of 90% NTSC-xy, while the color gamut of the original LCD with the white LEDs containing YAG:Ce phosphor was 71% NTSC-xy. The improvement of the brightness of the LCD with the phosphor sheet was studied. Encapsulates with a greater curvature on blue LEDs used with the phosphor sheet can increase the brightness. The brightness of the LCD with the phosphor sheet and blue LEDs with the spherical encapsulates of which the curvature = about 0.7 was estimated to reach to 85% of that of the original LCD. The simpler phosphor sheet with the aluminum film edge seals was also developed. It was confirmed that it has sufficient reliability during storage and operation at high temperature and high humidity and there is no difference in its reliability between the edge area and the center area. The importance of the moisture barrier layers which protect the SrGa2S4:Eu and CaS:Eu phosphors was confirmed. The phosphor sheet with the moisture barrier layers had better reliability than that with the PET layers.

Combustion experiments of fuel droplet array in fuel-vapor/air mixture were performed at normal and microgravities to investigate mechanism of flame spread. A 10-droplet array was inserted into the test section filled with a saturated fuel-vapor/air mixture as a simple model of prevaporized sprays. Gas equivalence ratio of the fuel-vapor/air mixture was controlled by the test section temperature. n -Decane droplets of 0.8 mm in the initial diameter were employed. The first droplet was ignited by a hot wire to initiate flame spread along a fuel droplet array. Sequential magnified backlit-images of the target droplets in the droplet array were taken during flame spread. From those images, ignition behavior of droplets at the vicinity of the leading edge of a spreading flame was observed. The onset of droplet-heating was obtained from the history of droplet diameter. The ignition of the target droplet was detected by the glowing of the suspenders. Ignition delay time was defined as the time difference between the onset of droplet-heating and the ignition of the droplet. Flame spread induction time was defined as the time difference between the ignitions of the neighboring droplets. Effects of droplet spacing and gas equivalence ratio on the ignition delay time were examined. Nondimensional droplet spacing S / d 0 and gas equivalence ratio were varied from 2 to 12.75 and from 0 to 0.5, respectively. The ignition delay time slightly decreased as the increase in the gas equivalence ratio at all normalized droplet spacings. In the range of S / d 0 S / d 0 , the time required for expansion of the thermal-effect zone of a flame occupied certain amount of the flame spread induction time. At 12.75 in S / d 0 , the ignition delay time was a dominant factor for the flame spread induction time.

Genetically encoded calcium indicators for visualizing dynamic cellular activity have greatly expanded our understanding of the brain. However, due to light scattering properties of the brain as well as the size and rigidity of traditional imaging technology, in vivo calcium imaging has been limited to superficial brain structures during head fixed behavioral tasks. This limitation can now be circumvented by utilizing miniature, integrated microscopes in conjunction with an implantable microendoscopic lens to guide light into and out of the brain, thus permitting optical access to deep brain (or superficial) neural ensembles during naturalistic behaviors. Here, we describe procedural steps to conduct such imaging studies using mice. However, we anticipate the protocol can be easily adapted for use in other small vertebrates. Successful completion of this protocol will permit cellular imaging of neuronal activity and the generation of data sets with sufficient statistical power to correlate neural activity with stimulus presentation, physiological state, and other aspects of complex behavioral tasks. This protocol takes 6–11 weeks to complete.

Two lithographic test masks, Stokes polarimeter mask and Mueller matrix polarimeter mask, are introduced. Both the masks comprise newly developed thin polarizers and wide-view-angle λ/4 plates. Photomasks are only 6.35 mm in thickness, and the illumination involves the oblique incidence of 20° at the most. Calcite plates thinned to less than 0.1 mm can perform as polarizers only at a wavelength of 193 nm. The combination of quartz and sapphire plates can mitigate the retardation change with angle of incidence. Stokes polarimeter and Mueller matrix polarimeter masks are used for the measurement of the illumination and the projecting optics, respectively.

A lithographic test pattern, the phase shift grating (PSG) z monitor, is introduced. Through the use of phase shift techniques, position errors of images in the z-direction translate into lateral shifts in the printed pattern. The lateral shifts are easily measurable using an overlay metrology tool. Each z monitor pattern in a test mask can be directly read for the sign and magnitude of the z error. When the experimental conditions, namely, the period of a PSG and a coherent factor of the lithography tool simultaneously satisfies a criterion of the asymmetric two-beam interference between the zeroth-order ray and either of the two first-order rays of diffraction, the linearity of a z-vs-overlay curve is always complete and the slope of the curve is constant everywhere in the image field. Using state-of-the-art overlay metrology tools, we realized subnanometer-order accuracy in the z measurement.

OBJECTIVE: We describe a new strategy to promote axonal regeneration after subacute or chronic spinal cord injury consisting of intramedullary implantation of chitosan guidance channels containing peripheral nerve (PN) grafts. METHODS: Chitosan channels filled with PN grafts harvested from green fluorescent protein rats were implanted in the cavity 1 week (subacute) or 4 weeks (chronic) after 50-g clip injury atT8 and were compared with similarly injured animals implanted with either unfilled channels or no channels. Functional recovery was measured weekly for 12 weeks by open-field locomotion, after which histological examination was performed. RESULTS: The implanted channels with PN grafts contained a thick tissue bridge containing as many as 35,000 myelinated axons in both the subacute and chronic spinal cord injury groups, with the greatest number of axons in the channels containing PN grafts implanted subacutely. There were numerous green fluorescent protein-positive donor Schwann cells in the tissue bridges in all animals with PN grafts. Moreover, these Schwann cells had high functional capacity in terms of myelination of the axons in the channels. In addition, PN-filled chitosan channels showed excellent biocompatibility with the adjacent neural tissue and no obvious signs of degradation and minimal tissue reaction at 14 weeks after implantation. In control animals that had unfilled chitosan channels implanted, there was minimal axonal regeneration in the channels; in control animals without channels, there were large cavities in the spinal cords, and the bridges contained only a small number of axons and Schwann cells. Despite the large numbers of axons in the chitosan channel-PN graft group, there was no significant difference in functional recovery between treatment and control groups. CONCLUSION: Intramedullary implantation of chitosan guidance channels containing PN grafts in the cavity after subacute spinal cord injury resulted in a thicker bridge containing a larger number of myelinated axons compared with chitosan channels alone. A chitosan channel containing PN grafts is a promising strategy for spinal cord repair.

Axonal dieback is a process in which axons in spinal tracts retract away from the initial site of injury. The purpose of this project is to study the dynamics of dieback in corticospinal tract (CST) axons after various time intervals post-injury, to find the optimal spatial-temporal window for regenerative treatment. Rats received transection injuries at the T8 spinal level and were sacrificed at different time periods (1, 2, 4, 8, and 16 weeks). Three weeks prior to sacrifice, DiI crystals were implanted in the sensorimotor cortex and produced excellent CST labeling, and clear delineation of the terminal bulbs of transected axons. With DiI and confocal microscopy, we visualized axons along the entire length of the CST, and quantified the temporal and spatial features of dieback in axons of the CST based on the location of the terminal bulbs. We found that the majority of axons stopped dieing back 4 weeks after injury by which time they were approximately 2.5 mm from the site of injury. However, at 8 and 16 weeks after injury, some terminal bulbs were more than 10 and 19 mm, respectively, from the site of injury.

Distributed propulsion systems have been investigated by many researchers because the propulsion system can enhance the benefits of unconventional airframe concepts such as blended wing body (BWB) aircraft. The core-separated fan propulsion system mostly considered for use in the distributed propulsion is unique compared to conventional jet engines because the propulsion fans are separated and the driving power is delivered from the core engines placed apart from the propulsion fans. Several power sources might be used, but the most promising one to realize ultralow fuel emission aircraft is electrical. This paper presents the background and the potential for research activities for the core-separated fan propulsion systems. One referenced turboelectric propulsion system was evaluated for validation using a new analytical tool. The authors are emphasizing the configuration of electric fan propulsion system powered by a SOFC-GT core. Benefits and challenges of that core configuration are explained.

Electrostatic spray deposition (ESD) was applied to fabricate a thin-layer of yttria-stabilized zirconia (YSZ) electrolyte on a solid oxide fuel cell (SOFC) anode substrate consisting of nickel-YSZ cermet. A colloidal solution of 8 mol% YSZ in ethanol was sprayed onto the substrate anode surface at 250–300 °C by ESD. After sintering the deposited layer at 1250–1400 °C for 1–2 h depending on temperature, the cathode layer, consisting of lanthanum strontium manganate (LSM), was sprayed or brush coated onto the electrolyte layer. Performance tests and AC impedance measurements of the complete cell were carried out at 800 °C to evaluate the density and conductance of the electrolyte layer formed by ESD. With a 97% H2/3% H2O mixture and air as fuel and oxidant gas, respectively, the open-circuit voltage (OCV) was close to theoretical and electrolyte impedance was about 0.23Ω cm2. A power density of 0.45 W cm−2 at 0.62 V was obtained. No abnormal degradation was observed after 170 h operation. The electrolyte sintering temperature and time did not significantly affect the electrolyte impedance.

Flame spread on a fuel droplet array has been studied as a simple model of spray combustion. A three-fuel-droplet array with a pendulum suspender was employed to investigate interactions between flame spread and droplet motion in the axial direction. Initial droplet diameter was 0.8 mm, and fuel was n -heptane. A silicon carbide pendulum suspender of 15 μm in diameter and 30 mm in length was used for the third droplet. The first fixed droplet was ignited by electric spark. Behavior of the flame and the third droplet was observed using a high-speed video camera with an image intensifier. Particle tracking velocimetry (PTV) measurements were performed to explain the behavior of the third movable droplet. The dimensionless droplet span, which is the average of droplet-to-droplet distances divided by the average initial diameter of the three droplets, was varied from 2.5 to 8 for observing flame spread, and fixed at 5.5 for PTV measurements. It was observed that the third droplet moved away from the second droplet before the flame spread to the third droplet. The displacement of the third droplet is remarkable when the dimensionless droplet span is close to the limit of flame spread. This implies that the movement of the droplet decreases the dimensionless span of the flame spread limit and the flame spread speed near the flame spread limit. Results of PTV measurements suggest that the heat expansion wave, caused by ignition of the premixture which was accumulated around the second droplet, and the burned gas flow from the second droplet pushed away the third droplet; then natural convection, induced by the flames of the first and second droplets, drew the third droplet to the second droplet. The heat expansion wave and the burned gas flow of the second droplet reached nearly 12 in dimensionless span.

The response of a wavelength shifting acrylic plastic has been determined for particles passing through the plastic and for Cherenkov light incident on the plastic from an external silica-aerogel radiator. The results have been obtained during a beam test at the KEK PS facility. The photoelectron yield for internally created Cherenkov light has been determined as a function of particle velocity. A comparison with an empirical parameterization gives rough estimates for the photon collection efficiency of 39% and 92% for internal Cherenkov emission below and above the critical angle for total internal reflection, respectively. A comparatively low efficiency of ≈13% for external light is likely due to losses in the external aerogel radiator.

Spark ignition characteristics of flanged spark plugs have been studied experimentally. Experiments were performed using a constant volume combustion chamber and a natural gas engine. Flanged spark plugs were made by remolding spark plugs on the market. The minimum ignition energy was employed to evaluate the ignition characteristics of the flanged spark plugs. It was found that the flanged spark plug reduces the minimum ignition energy. It was observed by schlieren photography that the shock wave was reflected by the flanges concentrated on a flame kernel. This fact suggests that the adiabatic compression due to the shock concentration reduces the minimum ignition energy. There is little effect of the flange on the flame speed, although it is well known that the existence of flanges prevents the initial growth of the flame kernel. It was found that, in actual engine test, the ignition probability is increased and the lean limit is extended.

An accurate method for measuring defocus, which is an application of phase shifting mask technology for higher resolution microlithography, reveals the impacts of reticle topography on optical microlithography. On the topographic reticles, there exist many focus monitors besides overlay marks. These reticles include almost flat and convex to concave topography with a maximum altitude difference of 2 µm. Contrary to our expectation, the experimental results showed that reticle topography has little impact on the field curvature, but has a significant impact on overlay errors. The lithography tool used in this experiment presses topographic reticles flatly against the face of a reticle stage to plane the field curvature, with generating magnification errors only in the slit direction.

A two-dimensional numerical analysis with elementary reactions including ion-molecule reactions has been performed to investigate the effect of energy deposition schedule on the minimum ignition energy in the composite spark ignition of methane/air mixtures. The chemical reaction scheme for a methane/air mixture, which has 27 species including 5 ion molecules and electrons and 81 elementary reactions with ion-molecule reactions, is employed in the calculation. Experiments are also carried out, and a qualitative comparison between experiment and calculation is made. The calculated result showed that the optimum ratio of capacity spark energy, for which the minimum ignition energy has a lowest value, exists. The increase in the capacity spark energy leads to a decrease in the formation of radicals during the spark discharge, while it also leads to an active reaction after spark discharge, which is due to the enhanced supply of the unburned mixture into the flame kernel by the inward flow along electrodes. The qualitative trend of calculated and experimental results shows good agreement for the relationship between the ratio of capacity spark energy and the minimum ignition energy. The minimum ignition energy obtained from the calculation with ion-molecule reactions is slightly larger than that without ion-molecule reactions. This may be due to the consumption of energy for ionization.

This paper shows numerical simulation results of a motor configuration suited to driving aircraft propulsion fans to elucidate the effects of the motor control parameters. Two experimental model results are shown to compare the present parametric analysis with the qualitative tendency of the motor concept. The parameters determined in the simulation were onset timing of the pulse, phase shift of the enamoring coils, rotation speed and input current. The results revealed several important control variables and underscored the possibility of optimizing the performance by changing the number of variables.

Measurement methods using overlay inspection tools have been established for wave-front aberrations in optical lithography lenses used for integrated circuit manufacturing. Three-beam interferometry and asymmetric two-beam interferometry can transform the wave-front aberrations at selected points on the lens pupil to lateral image shifts for fine grating objects. A technique of overlapped exposures makes the image shifts of inner lines of the grating images optically measurable, even if the images are too fine to be resolved optically. These methods are available in the fields of integrated circuit manufacturing and lithography tool assembling. This paper sums up measurement methods for wave-front aberrations. It is experimentally estimated that the methods are equally matched with the phase measuring interferometry widely used in the tool assemblies respecting accuracy and precision.

A focus monitor reticle having a novel grating structure is proposed. If a grating pattern has a property of being able to generate asymmetry between positive and negative diffraction orders, a defocus of the grating pattern can be translated to an easily measured pattern shift perpendicular to the optical axis. A possible grating for this purpose is composed of three components: opaque line, naked line and #x03C0;/2-phase-shifted groove. In particular, with their width ratio equivalent to 2/1/1, one of the two first-order beams disappears entirely. Consequently, tilted standing waves are formed by two-beam interference between zeroth-order and the other first-order on the image plane. This paper describes a new technique for measuring a defocus with a phase shift grating object. Good agreement between experimental sensitivities and theoretical expectation verifies that the technique achieves high accuracy of several nanometers or better. Applications of the technique show indicative ability in field curvature and astigmatism of the state-of-the-art scanner.

The three-beam interference technique with high coherent illumination is considered promising for application to the measurement of lens aberrations due to its ease of use and convertibility of the results to Zernike coefficients. The coefficients widely describing the characteristics of aberrations are crucially important for the prediction of aberration impacts on a specific pattern, and are expected to minimize the impacts. Furthermore, intensive study of the three-beam interference technique is necessary for highly accurate prediction. This paper discusses the expected characteristics of three-beam interference based on theoretical considerations and experimental results. In one experiment, a krypton fluoride excimer laser scanner with a numerical aperture of 0.68 was used. Having practicable highly coherent illumination affects sensitivity in detecting aberrations, and makes results independent of exposure dose and focus. Such characteristics improve repeatability under realistic conditions that the exposure dose is not uniform and the wafer surface is not flat.

Complex relative amplitude transmittance ρ = T p /T s of extreme ultraviolet transmission multilayers fabricated to three numbers of layers has been evaluated by ellipsometry with synchrotron radiation at a photon energy of 97 eV. Large phase shifts enough to be a quarter-wave plate and a half-wave plate have been observed with respective transmittances of 10 and 0.5%.

To improve the current waveform of diode rectifiers, we propose a new operating principle for the voltage-doubler diode rectifiers. In the conventional voltage-doubler rectifier circuit, relatively large capacitors are used to boost the output voltage, while the proposed circuit uses smaller ones and a small reactor not to boost the output voltage but improve the input current waveform. A circuit design method is shown and confirmed experimentaly. The experimental results of a 1.6kW rectifier show that the proposed diode rectifier satisfies the harmonic guide lines. A high input power factor of 97% and an efficiency of 98% are also obtained. The new rectifier needs no controlled switches to meet the harmonic guide lines, resulting in a simple, reliable and low-cost ac-to-dc converters in comparison with the boost-type current-improving circuits.

A basic study of spray combustion has been made with a rapid expansion apparatus that can produce monodispersed fuel droplet clouds. The rapid expansion apparatus, which is essentially Wilson's cloud chamber, generates droplet clouds by reducing the pressure of saturated fuel vapor air mixtures. For droplet clouds more than 15 μm in mean droplet diameter, experiments were performed under microgravity conditions to prevent droplets from falling down by gravity. The mean diameter of droplet clouds was obtained from the laser lights scattered by droplets. Ethanol was used as a fuel. Pressure and total equivalence ratio were set 0.2 MPa and 0.8. The mean droplet diameter d m and the ratio of the liquid fuel mass to the total fuel mass were varied in the range of 8–24 μm and 0%–45%, respectively. Almost monodispersed and mono-sized droplet clouds were generated and ignited successfully under normal and microgravity conditions. Two types of flame propagation were observed. For the mixtures less than about 20 μm in mean droplet diameter, flames propagate in a smooth spherical shape like premixed gas flames. For the mixtures more than about 20 μm in mean droplet diameter, flames propagate in a rough spherical shape after the flames grow up to about 20 mm in diameter. The flame speed of the fuel droplet-vapor-air mixtures decreases with the increase in the mean droplet diameter of the mixtures. In the mixtures of d m

Performance of a Ru/Si multilayer polarizer of the double-crystal monochromator type is evaluated in the soft x-ray region. Its polarization was found to be higher than 99.5% at 89 and 97 eV.

For immersion lithography with aggressive polarization illumination settings, it is important to newly construct two systems for diagnosing lithography tools; Stokes polarimetry of illumination and Mueller matrix polarimetry of projection lenses. At the SPIE conference on Optical Microlithography XXI in 2008, the authors had already reported on the former Stokes polarimetry. True polarization states of several illumination settings emerged. On the other hand, the latter Mueller matrix polarimetry is thought more complicated than the Stokes polarimetry. Therefore, the Mueller matrix polarimetry is reported separating into two papers. A theoretical approach to realizing the polarimetry has reported at the SPIE conference on Lithography Asia 2009. The test mask for the Mueller matrix polarimetry also comprises thin-plate polarizers and wide-view-angle quarter-waveplates, both which are developed by collaboration with Kogakugiken Corporation in Japan. Mueller matrices of the sample projecting optics are reconstructed by sixteen measurements of Stokes parameters of a light ray that reaches the wafer plane though the test mask and the projecting optics. The Stokes parameters are measured with a polarization measurement system already equipped on a side stage lying at the wafer plane. It took about seven hours to capture all the images at five image heights within the static exposure field. Stokes parameters are automatically calculated from the images and outputted from the lithography tools as a text file, and Mueller matrices are calculated by homebuilt software in a short time. All the images were captured under the identical illumination condition that the tool manufacturer calls "un-polarization".

Fiber optic sheets (10 lines/mm) have been made by a new technique in which a monomer is diffused into a ridged polymer film with a higher refractive index and then polymerized by gamma-ray irradiation. The diffusion profile was controllable from the clad type to the self-focusing type by adjusting the diffusion conditions. The attenuation in the polycarbonate light path (n = 1.59), enclosed with the chemically fixed methyl acrylate polymer (n = 1.49), was 0.5-0.7 dB/cm lambda = 633 nm.

It will be required for more accurate lithography simulation of complicated mask patterns then ever, under hyper-NA (numerical aperture) projection lens and aggressive small-aperture polarized-light illumination, to construct two systems of polarimetry; one is polarimetry for illumination, and the other is Mueller matrix polarimetry for projection lenses. The former polarimetry already reported by the authors is necessary for us to appreciate how the true polarization state of illumination is. The polarimeter mask described in the paper determines illumination polarization states by Stokes parameters. The latter polarimetry is the main subject of this paper. A Mueller matrix is a translation matrix of the input Stokes parameters to the output Stokes parameters. With the full elements of the Mueller matrix of a projection lens, the Stokes parameters of a light at the wafer plane can be easily predicted from the Stokes parameters of any illumination conditions. This paper proposed a new method of Mueller matrix polarimetry and a monitor mask used for 193-nm immersion lithography tools with a polarization monitor at the wafer plane.

It is well known that the state-space averaging models of the boost and the buck-boost converters are bilinear systems. The stability and output regulation problems of bilinear systems are so complicated that most previous works which deal with the above two types of converter in the state space are confined to the analysis of linear approximated systems (small signal models). However, any control law for small signal model does not generally guarantee the global stability, but the partial stability of the system.A new control law based on the bilinear large signal model is proposed for achieving output regulation of the boost and the buck-boost converters. The control law is derived from directly applying the Lyapunov stability theory to the bilinear large signal model. The acutual realization of this control law might have some difficulties, because it is given as a solution of differential equations with respect to the state and input variables. However the closed loop system with this control law is expected to possess the robust stability achieving an excellent output regulation for large changes of reference, load and source voltage from the theoretical point of view. Some desirable features of the new control law are demonstrated by the numerical simulation.

Ellipsometry is defined as a technique for determining the properties of a bulk material or a thin film, such as optical index and thickness, from the measurement of a polarization state of a reflected light or a change of polarization states between the incident and reflected lights. On the other hand, polarimetry is defined as a technique for determining a polarization state of a light. In other words, ellipsometry uses polarization as a probe and polarimetry measures polarization itself. We have constructed a theory of polarimetry of illumination used in lithography equipments, fabricated a polarimeter mask, and demonstrated it for a hyper-NA (numerical aperture) immersion lithography scanner. The polarimeter mask comprises polarizers and quarter-wave (λ/4) plates that are crammed into a narrow space with a height of 6.35 mm. The thin plate polarizers available at a wavelength of 193 nm are made of calcite, and the λ/4-plates insensitive to angle of incidence are made of four thin plates, two of which are crystalline quartz; the other two are sapphire. A light traveling through a window of the polarimeter mask reaches an image detector at the wafer level through projection optics. Stokes parameters of the illumination light can be measured without any influence from polarization characteristics of the projection optics between the mask and the image detector.

Techniques for measurement of higher-order aberrations of a projection optical system in photolithographic exposure tools have been established. Even-type and odd-type aberrations are independently obtained from printed grating patterns on a wafer by three-beam interference under highly coherent illumination. Even-type aberrations, i.e., spherical aberration and astigmatism, are derived from the best focus positions of vertical, horizontal, and oblique grating patterns by an optical microscope. Odd-type aberrations, i.e., coma and three-foil, are obtained by detection of relative shifts of a fine grating pattern to a large pattern by an overlay inspection tool. Quantitative diagnosis of lens aberrations with a krypton fluoride (KrF) excimer laser scanner is demonstrated.

In optical lithography, it is a serious problem that aberrations in projection lenses reduce the imaging quality. Therefore techniques to measure the aberrations are required that will predict the adverse effects of aberrations on lithographic imagery and reduce them. We present a measurement method that uses a fine grating and its imaging condition to quantify coma, astigmatism, and spherical aberration. With this method, these aberrations can be described with simple expressions from the measured results. Application of this method revealed the coma of Zernike polynomials for our krypton fluoride (KrF) excimer-laser scanner.

We have constructed a theory of polarimetry of illumination used in 193-nm lithography equipments, fabricated a polarimeter mask, and demonstrated it for a hyper-NA (numerical aperture) lithography scanner. The polarimeter mask comprises newly- developed polarizers and quarter-wave (λ/4) plates. The thin plate polarizers are made of calcite (CaCO3), and the λ/4 plates are composed of two crystalline quartz (α-SiO2) plates and two sapphire (Al2O3) plates. A light traveling through a window of the polarimeter mask reaches an image detector at the wafer level through projection optics. Whereas the polarization states of the projection optics are unknown to us, Stokes parameters of the illumination light are formulated without any influence from the projection optics.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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.

Phase shift versus incident angle characteristics of soft x‐ray multilayer mirrors have been studied for the first time by rotating analyzer ellipsometry at 97 eV photon energy. Synchrotron radiation was used as a linear polarization source and a multilayer polarizer of 97% polarizance was used as the analyzer. By the reflection at two multilayers mounted in the double crystal configuration, circular polarization was produced. This confirmed a total phase shift of 90° and proved the usefulness of the multilayer as a phase shifter for polarization evaluation.

Measurement techniques for higher order aberrations of a projection optical system in photolithographic exposure tools have been established. Even-type and odd-type aberrations are independently obtained from printed grouped lines on a wafer by three-beam interference under highly coherent illumination. Even-type aberrations, i.e. spherical aberration and astigmatism, are derived from the best focus position of vertical, horizontal and orthogonal grouped lines by an optical microscope. Odd-type aberrations, i.e. coma and trefoil, are obtained by detecting relative shifts of fine grouped lines to a large pattern by an overlay inspection tool. The qualitative diagnosis for lens aberrations was demonstrated to a krypton fluoride excimer laser scanner.

Coma aberration of projection optics and asymmetric illumination degrade a resist profile symmetricity and enhanced a placement error which depend on pattern size, density and feature. Relative displacements between 2.0 micrometer isolated lines and sub-micron periodic lines are measured to characterize the coma aberration and the illumination telecentricity. A conventional overlay inspection tool and bars-in-bars marks are used for this evaluation. It is difficult to measure the placement error of periodic patterns because their inner patterns have a different placement error from their both ends. The differences in line- width between both ends of periodic lines are caused by the differences in placement errors between their inner and their both ends patterns. The measurement marks for periodic lines are fabricated by the double exposure of two marks. When the resist patterns are imaged by the interference of only three diffracted beams, the coma aberration of Zernike's polynomials can be calculated by the simple expressions from the measurement results. We derived the condition of coherency (sigma) and pattern pitch P which satisfy the imaging of only three diffracted beams. The coma aberration is estimated to be 0.12 wavelength at maximum for the exposure system we applied. In this method, the focus is not so important for the accurate measurement because the measurement data remain constant at any foci. It takes only one hour to estimate the coma aberration completely including a sample making (sample making: 0.5 h, measurement/evaluation: 0.5 h). The relative pattern shifts between large patterns and fine patterns could be usually caused by not only coma aberration but also illumination optics. The telecentricity of the illumination optics is also discussed in this paper.

A lab-scale combustion wind tunnel was developed for investigation of low-pressure ignition and flame holding in a sub-scale pre-cooled turbojet engine with hydrogen fuel in order to make engine start at high altitudes sure. The combustion wind tunnel is a blow-down type. A fuel injector of the sub-scale pre-cooled turbojet engine was installed into the combustion wind tunnel. Conditions in which a flame can be stabilized at the fuel injector were examined. The combustor pressure and equivalence ratio were varied from 10 to 40 kPa and from 0.4 to 0.8, respectively. The mean inlet air velocity was varied from 2 to 48 m/s. Flames stabilized at 20 kPa in pressure and 0.6 in equivalence ratio were observed. It was found that the decrease in the combustor pressure narrows the mean inlet air velocity range for successful flame holdings. Flame holding at lower combustor pressures is realized at the equivalence ratio of 0.4 in the low mean inlet air velocity range, and at the equivalence ratio of 0.6 in the high mean inlet air velocity range. Flame luminosity is the largest near the fuel injector. The flame luminosity distribution becomes flatter as the increase in the mean inlet air velocity.