Table of contents

Ultrasonic imaging and scanned acoustic microscopy are terms used to describe similar imaging processes at different magnifications and frequencies. Both processes form images by acquiring spatially correlated measurements of the interaction of high-frequency sound waves with materials. With the exception of the interference measurement, called V(z), and the gigahertz frequencies used by the higher frequency scanning acoustic microscopes, it is difficult to establish operational differences between them. This is especially true since almost all commercial ultrasonic imaging systems use transducers producing focused beams and can display magnified high-resolution images.

Ultrasonic C-scan imaging was developed largely by the ultrasonic nondestructive testing industry. The development was gradual and evolutionary. Over a 50-year period, better and better broadband transducers, electronics and scanners were developed for operation at progressively higher frequencies, now ranging from 1.0 to 100 MHz. Conversely, scanning acoustic microscopes made a relatively sudden appearance 20 years ago on the campus of Stanford University. The first scanning acoustic microscopes operated at gigahertz frequencies and used microwave electronics that produced acoustic tone bursts with many wavelengths per pulse.

Three factors control resolution in an acoustic image:

diameter of the acoustic beam or its point spread function (PSF);

size and spacing of the pixels making up the image;

signal-to-noise ratio (contrast) of the feature being resolved.

The beam diameter, or PSF, is controlled by the frequency of the ultrasonic pulse and the focal convergence of the beam (or focal length to diameter ratio Z/d). In the coupling fluid, the Z/d ratio is determined by the transducer diameter and lens, but in the material, Z/d is established by the materials ultrasonic velocities. Pixels are the squares of colour or greyscale that make up computer displays of scanned images. Following Nyquist's criterion, the resolution of those images is twice the size and spacing of the pixels. It follows, therefore, that in order to support the resolution of an ultrasonic beam, the pixels must be no larger than half that beam diameter. Finally, the contrast of the feature being studied must be (at least) a clear shade of grey above the background produced by the image noise. The noise can be due to the material or the electronics.

Written to support industrial ultrasonic inspection of materials, this discussion will emphasise the similarities between imaging and microscopy rather than the differences. The roles of the focusing lens, the pulse frequency, and the material being imaged, with respect to the final resolution of an acoustic image, will be considered in detail. It will be shown that additional improvements in resolution can be achieved with image processing. Finally, applications studies in metals, ceramics, composites, attachment methods, coatings, and electronic assemblies will be used to demonstrate specific roles for imaging/microscopy in nondestructive testing.

Coherent Foucault (CF) imaging has been implemented in a transmission electron microscope to obtain magnetic interferograms of micrometre-sized permalloy elements fabricated by electron beam-lithographic and evaporation techniques. The interferograms provide a quantitative description of the distribution of flux throughout the elements. We have observed how this changes under the influence of applied magnetic field and temperature variation. Results are presented for rectangular elements of thickness 30 nm. From the magnetizing experiments, details of the transformation between solenoidal and non-solenoidal magnetization distributions are revealed, whereas the heating experiments show how domain structures are modified as the temperature of the element is increased from room temperature to beyond the Curie point.

The paramagnetic - antiferromagnetic transition for an Fe - 31Mn - 3Al - 7Cr alloy was investigated by measurements of the susceptibility , the elastic modulus (E), the resistivity and the strain sensitivity coefficient of resistance (K). The results show that the alloy is a typical localized antiferromagnet. It has minima in the - T and E - T curves at the same temperature below the Néel temperature . The strain sensitivity coefficient of resistance (K) decreases drastically near and it tends to be stable when the temperature exceeds . A novel interpretation relating to the stress sensitivity coefficient of resistance (B) is proposed. The paramagnetic - antiferromagnetic transition has a much greater effect on B than it has on E; the temperature dependence of K is the same as that of B. It is suggested that the effect of stress on the energy band of the alloy may be the reason for the drastic change in K near and that the temperature dependence of K may be a new basis for understanding the energy gap in an antiferromagnetic alloy.

The bilocal approximation is used along with the strong property fluctuation theory (SPFT) to homogenize (i.e. estimate the effective constitutive properties of) a chiral-in-chiral composite. Important properties of the covariance function of the spatial distribution of the two materials are deduced and interpreted with respect to the homogenization results. Comparison is made with the Maxwell Garnett and the Bruggeman approaches. The correlation length is an additional parameter that distinguishes the SPFT in the bilocal approximation from the Bruggeman approach (as well as from the Maxwell Garnett approach). The SPFT in the bilocal approximation turns out to be a size-dependent extension of the Bruggeman approach, the two homogenization procedures yielding almost the same results at very long wavelengths but not at shorter wavelengths.

A semi-empirical formula is given which allows one to calculate the total thermal cross section of an imperfect single crystal as a function of crystal constants, temperature and neutron energy E, in the energy range between 3 meV and 10 eV. The formula also includes the contribution of the parasitic Bragg scattering to the total cross section that takes into account the crystal mosaic spread value and its orientation with respect to the neutron beam direction. A computer program (ISCANF) was developed to calculate the total attenuation of neutrons using the proposed formula. The ISCANF program was applied to investigate the neutron attenuation through a copper single crystal. The calculated values of the neutron transmission through the imperfect copper single crystal were fitted to the measured ones in the energy range 3 - 40 meV at different crystal orientations. The result of fitting shows that use of the computer program ISCANF allows one to predict the behaviour of the total cross section of an imperfect copper single crystal for the whole energy range.

Results from numerical experiments and direct measurements for the analysis of an axially symmetric triode electron gun with thermionic cathode for electron beam welding are presented and discussed. Computer simulation is carried out using the new version of the GUN-EBT software package. The self-consistent model takes into account the energy spectrum of emitted electrons and formation of a potential minimum in front of the cathode. The method underlying the investigation incorporates not only the commonly used trajectory analysis (ray tracing) but also an analysis in the phase space (phase analysis) which allows the emittance of the beams to be evaluated. It is demonstrated that computer simulation of beam formation provides ample information for the assessment both of the quality of generated beams and operational performance of the guns.

Over recent years there has been great efforts towards the understanding of the rheology of immiscible polymer blends. It is now well accepted that their morphology, especially the concentration of the inclusions, their size, and their radii distribution, is a very important factor which controls their mechanical properties. The type of blend considered in this study is a polyamide/polypropylene system, in which the matrix is the polyamide (PA6) with inclusions of polypropylene (PP). Different concentrations have been used, as well as different surfactants. These blends give then rise to different acoustic properties, which have been characterized by measuring velocities of propagation and attenuation of ultrasonic waves during flow through a capillary rheometer. A wave propagation theory for viscoelastic emulsions was used to predict the values of the ultrasonic parameters as functions of the concentration, the radii distribution and the frequency when the thermophysical properties of the blend are known. We can therefore deduce the concentration and average size of inclusions, and then return to the morphology of the blends. Comparison with microscopic photographs seems to correlate well with our predictions. This method appears promising and could be used to differentiate between different blends during flow.

Using an improved Brayton cycle as a model, a general analysis accounting for the efficiency and net power output of a gas-turbine power plant with multiple reheating and intercooling stages is presented. This analysis provides a general theoretical tool for the selection of the optimal operating conditions of the heat engine in terms of the compressor and turbine isentropic efficiencies and of the heat exchanger efficiency. Explicit results for the efficiency, net power output, optimized pressure ratios, maximum efficiency, maximum power, efficiency at maximum power, and power at maximum efficiency are given. Among others, the familiar results of the Brayton cycle (one compressor and one turbine) and of the corresponding Ericsson cycle (infinite compressors and infinite turbines) are obtained as particular cases.

The temperature separation effect, which is well known from standard vortex tubes that are driven by compressed air, has been observed in a device where air is sucked into the tube by applying vacuum at the hot and the cold exit ports. Rather than depending on the absolute inlet pressure, the temperature separation was found to be a linear function of the normalized pressure drop between the inlet and the cold end of the vortex tube.

An analysis of the thermal efficiency of a magnetohydrodynamic (MHD) power cycle at maximum power density for a constant velocity type MHD generator has been carried out. The irreversibilities at the compressor and the MHD generator are taken into account. The results obtained from power density analysis were compared with those of maximum power analysis. It is shown that by using the power density criteria the MHD cycle efficiency can be increased effectively.

The theory of perturbation is used to describe electron rate coefficients in gases under non-uniform field and electron-density conditions when the deviation from spatial uniformity is small. It is shown that the space-dependent rate coefficients can be represented as a sum of the local values and the product of new rate coefficients dependent on the local field and the gradients of the field and of the electron density. By solving the Boltzmann equation in a two-term approximation, the new rate coefficients are calculated for , , and Ar. The results of our calculations are compared with experimental data on the relative excitation rates in a steady-state Townsend discharge in a mixture and with results of previous Monte Carlo simulations of the electron swarm behaviour in non-uniform fields.

The diffusion of a potassium plasma in a magnetic field has been investigated under conditions in which a relatively large fraction of the electrons is attached to molecules. The experiments were performed in a double-ended Q-machine. Upon collision with a negative ion, the ions experience a displacement across the magnetic field of the order of their gyroradius, leading to an enhancement in the rate of cross field diffusion over that expected in an ordinary - electron plasma.

A closed 13.6 MHz inductively coupled argon plasma with a volume of is investigated by active and passive diagnostics. The study considers the influence of varying argon filling pressures in the range 10 - 100 mbar and different input powers in the range 50 - 125 W. The combination of the applied techniques of absolute line emission intensities, Thomson scattering and diode laser absorption measurements reveals the typical behaviour of temperature and electron density of the plasma. One of the observed characteristics is that, upon increasing the filling pressure, the ring-shaped radial distribution of the electron density becomes more pronounced, while the electron temperature decreases over the whole radial profile. Furthermore, the influence of input power on the electron temperature and density depends strongly on the filling pressure. It is to be expected that insight into plasma processes and parameters for argon filling will lead to a better understanding of future light sources as well.

An original experimental apparatus of microwave plasma-assisted chemical vapour deposition is used to produce large cylindrical plasmas. The microwave electromagnetic field propagation is studied experimentally and theoretically in the plasma chamber. Electric field measurements confirm this calculation. The electronic density distribution is calculated in a second way from transport equations using a perturbation method. A validation of the model is obtained by measuring particle densities using a Langmuir probe.

Heavy particles bombarding the cathode surface in a glow discharge produce sputtering which liberates cathode material which then appears in the plasma phase in the vicinity of the cathode. The intensity of light emission from fundamental gas atoms depends linearly on the discharge current and this dependence can be explained if it is assumed that these intensities are proportional to the densities of the gas and electron current density. The electron/molecule excitation of sputtered material in the plasma phase is the main source of the light emitted by elements of the cathode. The intensity of light emission from this cathode material in the plasma depends parabolically on the discharge current density. This dependence can be explained if the intensity is assumed to be proportional to the densities of both the electron current and the stream of sputtered particles leaving the cathode surface. The density of the sputtered particles is in turn dependent on the energy of bombarding particles. The excitation of the sputtered material due to fast particle interaction with the cathode bulk seems to be a less important mechanism of light emission.

Shock-wave generation by the laser-heated plasma ablation is studied by extending the existing models. Fluid parameters characterizing the process of laser-driven ablation and ablation-driven shock are derived and expressed as functions of the ratio between the light pressure and the thermal pressure of the plasma.

The demixing effect in a wall-stabilized arc leads to sulphur depletion in the central part of the arc where the ratio between fluorine concentration and sulphur concentration becomes higher than six. We have calculated material functions for different real or fictitious gases , with (specific heat, electrical and thermal conductivities, net emission coefficient) and used them in a one-dimensional model based on Patankar's algorithms. The electric field and the temperature radial profile have been calculated versus the current intensity using 5 mm and 3.2 mm arc diameters. Comparison with experimental results in the literature shows that the influence of demixing on the axis temperature is greater than the experimental error. Thus, we conclude that validating material functions of plasma by comparing experimental and theoretical values of temperature in wall-stabilized arcs needs to take into account demixing effects.

It is demonstrated that the use of LIF spectroscopy of CS molecules provides sensitive measurements of plasma electric fields with high spatial resolution. The experiment was performed in a helium glow discharge which was produced in a discharge vessel applying a voltage to two gold-plated electrodes (60 mm in diameter, 40 mm spacing). The CS molecule admixture was generated by a rf discharge in a gas flow system outside the discharge vessel. The plasma parameters in the negative glow discharge were obtained by probe measurements. The electron density was about and the electron temperature was 0.2 eV on the discharge axis for , and helium gas pressure . The measured electric field strength was in the range of and its spatial distribution in the cathode fall region is in good agreement with cathode fall theory.

Using a dynamical z-pinch discharge, intense radiation of hydrogen-like carbon was produced. Operating the discharge with a maximum current of 105 kA and a period of 274 ns, the Balmer transition at 18.23 nm appeared as a short (< 8 ns FWHM) and bright (230 kW in ) peak emitted from a cylindrical volume with a radius of at the centre of the vessel. The results are compared with predictions of models for a z-pinch discharge. Optical gain for the Balmer transition was determined to be less than in agreement with the prediction of the model.

A method for estimating metallic vapour concentration in a post-arc channel on the basis of a spectroscopic method was proposed. Using the method, the axial distribution of metallic vapour concentration in a post-arc channel was measured around the nozzle throat in a flat-type gas-blast quenching chamber. In the chamber iron was intentionally used as an electrode material since Fe spectral lines at wavelengths of 426.0 and 442.7 nm have very much higher radiation intensities than particles such as , F or Cu at temperatures below 6000 K. The proposed method was capable of determining the iron vapour concentration up to after current zero in the experiment. It was found that has a magnitude around % along the nozzle axis during the period from -60 to after current zero for 5 kA arcs.

This paper investigates the stability of simple static orientation patterns in a sample of nematic liquid crystal confined to a cylindrical annulus, when a magnetic field is applied. Six different arrangements are considered, covering all the cases in which the (mutually orthogonal) magnetic field and initial director field are either radial, azimuthal or axial. A classification is given of the threshold fields for Freedericksz transitions for these six cases, with either strong anchoring or weak anchoring at the boundaries, with or without an `easy axis' specified. The weak anchoring cases are of particular interest, since they lead to a dependence of the critical fields on the elastic constant and on various anchoring constants, thereby providing possible means of measuring these quantities.

The concept of radiation hardness of semiconductor materials in terms of local charge neutrality is proposed. Deep centres are invoked to play the basic role in the attainment of radiation hardness by high-resistivity semiconductor charged particle detectors exposed to neutron irradiation.

KrF excimer laser ablation in air at an ambient pressure of 1 bar leads to an intense evaporation of target material. The ablated material compresses the surrounding gas and leads to the formation of a shock wave. The incident laser radiation interacts with the compressed, ionized ambient gas behind the shock front and the partially ionized material vapour. This interaction is responsible for extinction of the incident laser radiation and exerts effects on the processing result and the efficiency of the treatment. The transmission of the incident laser power through the laser-induced interaction zone was measured using a target foil prepared with a small aperture within the area of irradiation. Extinction coefficients in the range were measured for PET, copper and aluminium. In order to explain the experimental results, a theoretical study of possible extinction mechanisms was performed on the basis of inverse Bremsstrahlung theory and scattering theories. The thermodynamic properties in the interaction zone were calculated by using a shock wave theory. Under the assumption that this theory describes the thermodynamic properties in a physically correct manner, it will be shown that inverse Bremsstrahlung cannot explain the measured small degrees of transmission. Interactions between the incident laser light and material clusters in the laser-induced material vapour, like Rayleigh scattering, however, can lead to values comparable to the experimental findings. In order to classify the scattered fraction from the incident laser power, information on the size of the scattering particles is necessary. Therefore, a simplified model of cluster condensation in the material vapour and the scattering of incident laser power by these clusters was developed. Theoretically obtained results on this basis will be compared with the experimental data.

Polarized UV - visible absorption and rotation-angle second-harmonic generation techniques were used to investigate the in-plane symmetry in Y-type Langmuir - Blodgett multilayers of a hemicyanine dye interleaved with the inert material arachidic acid. Dipping-induced anisotropy of the molecular orientation with a unique reflection symmetry was enhanced with increasing dipping speed.

Ion beam analysis data are presented on both freshly prepared and `aged' porous silicon layers of widely varying (10 - 85%) porosity. Both evaporated Al and PECVD surface capping layers are shown to suppress some of the rapid ion beam induced changes in chemical composition that have been reported during analysis of uncapped layers. Specifically, these capping layers were successful in eliminating carbon and oxygen accumulation within the material but they only slightly reduced hydrogen loss under ion bombardment. Evaporated aluminium surface capping layers were partially successful in suppressing long term ambient oxygen pick-up.

This paper reports experiments in which methyl ions and hydrogen ions are generated and accelerated within a plasma plate array so that they interact with neutral methane molecules on the inside surfaces of a set of microchannels. The impact energies of the ions are in the range 10 eV to greater than 100 eV. The energy delivered in interactions at the surfaces causes the production of larger hydrocarbon molecules such as , and as well as molecules containing , , , , and .

The harmonic peaks along the dimension in the two-dimensional COSY NMR spectrum of liquid water are analysed in terms of radiation damping line shape theory. In the case of strong radiation damping, during the evolution period the angle , which describes the deviation of the magnetization from the direction, becomes time-dependent and modulates the 2D free-induction decay in a complicated way. Thus multiple frequencies are introduced into the oscillation of , which is the 2D signal after 1D Fourier transformation with respect to . The harmonic peaks have been well simulated.

Thermal treatment of LiF:Mg, Cu, P in the range 80 - performed after typical annealing at for 10 min causes important modifications to the glow-curve structure and to the behaviour of the individual glow-peaks. The maximum glow-peak temperatures and the activation energies obtained by a glow-curve de-convolution procedure are varied as a function of pre-irradiation annealing at temperatures below . Initial rise measurements support the results obtained by the glow-curve de-convolution concerning the high values of the activation energy of glow-peak 4, as well as its variation as a function of the pre-irradiation annealing. The `prompt' isothermal decay of glow-peak 4 at temperatures just below the maximum peak temperature consists of three components instead of one, which would be expected from the kinetic models. The second component corresponds to glow-peak 4 and also presents very high E and s values. The third one corresponds to a glow-peak at the high-temperature tail of peak 4. The first component was attributed to a mechanism competitive to the mechanism responsible for the main peak 4.

When using microfocus x-ray sources for x-ray imaging (x-ray projection microscopy or microradiography), the measured intensities are influenced by the non-monochromaticity of the incident x-ray beam. This affects the transmitted signal in the image pixels and consequently brings about errors in quantitative measurements by x-ray absorption analysis or in tomographic reconstruction. A model developed to predict the spectral distribution of x-rays generated by electron bombardment on a metallic target has been modified to be adapted to transmission targets. It is used here, in combination with a semi-empirical analytical expression for mass attenuation coefficients, to calculate the overall energy transmitted to an x-ray imaging system and thus to simulate any x-ray projection experiment. In particular, spectral purity, which is a measure of the degree of monochromaticity, can be easily evaluated. In this paper simulations are used to evaluate the effect of each part of an imaging system on the spectral purity. Here we are concerned with the effect of target and/or filter thicknesses and the influence on the purity of the selective absorption efficiency of phosphor screens with x-ray energy. As an example, three targets and two kinds of phosphor screen widely in use in x-ray CCD cameras have been considered.

A theoretical model is presented to describe the isothermal annealing of semiconductors partially amorphized by ion bombardment. The annealing behaviour of amorphous zones is approximated by first-order reaction kinetics and the increasing complexity of amorphousness with the fraction of material amorphized is approximated by a population of activated processes for which the mean activation energy increases with fractional amorphization. The model predictions are compared with limited available experimental data and shown to give satisfactory qualitative agreements and suggestions are made for model refinement.

Monte Carlo simulations have been used to study the influence of the magnetic field on ion impact at the cathode surface of a sputtering magnetron discharge. The ion parameters (energy, incident angle at the cathode and transit time) have been investigated under four magnetic field strengths and two pressures (1 and 10 Pa). It has been confirmed that the magnetic field has little influence on ion motion. Also, it was found that the magnetic field's influences on ion parameters are given through its influence on electron motion, namely on the ionization site, which is most important in determining the ion energy and transit time. It is proposed that, taking into consideration both the ion energy and the transit time, the appropriate ionization site is the edge of the cathode fall region.

Strontium barium niobate (SBN) thin films were grown on Si (111) substrates coated with MgO buffer by the pulsed laser deposition (PLD) technique. The thickness of SBN and MgO films were of the order of 1200 nm and 840 nm respectively. X-ray energy dispersive spectrometry (XREDS) showed that SBN films have stoichiometric composition identical to the target material, and no Si diffusion into the SBN film was found. X-ray diffraction (XRD) scans indicated that MgO films were highly (111) textured, but the SBN films were polycrystalline without preferential orientation. The surface of the SBN film was smooth, dense and crack-free and no large droplets were observed when studied under a scanning electron microscope (SEM). A favourable optical waveguiding property of the bilayered films was demonstrated by a prism coupler method.

The growth of microcrystalline silicon () films by plasma enhanced chemical vapour deposition (PECVD) of silane in the temperature range 200 - has been investigated. The growth system was a capacitively coupled parallel plate radio frequency (rf) glow discharge reactor in which the substrates were mounted on the cathode (powered electrode). It was found that films could be grown using 100% at a substrate temperature above with a high deposition rate and high degree or crystallinity. The main effect of mesh attachment was found to be the reduction of ionic bombardment to the film growth zone which prevents the degradation of surface crystallinity. It was also found that both P- and B-doped films with good optoelectronic properties could be grown using 100% .

Problems associated with the thresholds for plasma production (and connected with it, the nonlinearity of microwave energy release) during irradiation of complex metal - dielectric targets by microwaves in a deep vacuum or in a high-pressure gas were studied. The discovered effect of the low threshold for plasma formation, for which no adequate model exists, may find a number of applications, in particular, in quasi-stationary current generation, gas-discharge rocket engines and microwave soldering.

A new method, based on Green's theorem, for calculating the electric fields produced by two-dimensional electrode arrays for the dielectrophoretic (DEP) characterization and manipulation of particles is presented. This method transforms the problem of solving the second-order differential Laplace equation for the electrical potential into an integral problem at the electrode plane. It relies on the knowledge of the electrical potential distribution on the electrode plane (the Dirichlet type boundary condition). The effectiveness of the method is demonstrated in the examples of an array of parallel electrodes under various voltage signal excitation modes. The field distributions so obtained are compared with those calculated by the numerical charge density method. Furthermore, an approach is described for utilizing boundary conditions for mixed Dirichlet and Neumann types as appropriate for realistic electrode configurations. Finally the method's applicability to two-dimensional electrode arrays and its significance for dielectrophoresis studies are considered. Because of its analytical nature, the Green's theorem-based method has many advantages over numerical simulations: (1) depending on the complexity of the electrode geometry, analytical expressions may be obtained not only for the potential distribution but also for the electric field and the time-averaged DEP force, circumventing the need for numerical differentiation; (2) accurate field and DEP force determinations can be made right up to the electrode plane and the electrode edges; (3) the approach is computationally much more efficient than numerical techniques.

The extremely high frequency stability attainable with a cryogenic all-sapphire Fabry - Pérot cavity is limited by temperature-induced length fluctuations of the sapphire spacer. This paper presents a method of measuring the temperature in the sapphire spacer at cryogenic temperatures. The two systems described are analysed to have precisions of 750 and 75 nK over measurement times of 1 s. The temperature is detected by monitoring the AC susceptibility at microwave frequencies. The temperature coefficient of the susceptibility originates from the paramagnetic contribution of residual chromium in the sapphire. Two microwave detection circuits are proposed and the noise limitations of each discussed. The optimal doping levels of the paramagnetic ion are found to be commonly available as residuals in commercially available sapphire crystals. We show that an optical frequency reference with an Allan variance of a few times for integration times up to 100 s can be achieved using this system.

The effect of systematic variation in hydrogen dilution and RF power density on the different properties (such as optoelectronic and structural properties and defect density) of hydrogenated amorphous silicon germanium alloy (a-SiGe:H) films, prepared at ultra-high vacuum () in a plasma-enhanced chemical vapour deposition multichamber system with a load - lock facility has been studied. Proper structural relaxation of the alloy matrix is controlled by the growth zone reactions. These grown zone reactions depend on the type and number density of reactive radicals and on their energy and momentum. All these factors, hence growth zone reactions, may be changed by variation of the interlinked parameters hydrogen dilution and RF power density. Another noteworthy point is the investigation of the dependence of the improvement in characteristics of single junction solar cells having a-SiGe:H intrinsic layers on that of material quality. Improvement of material quality may or may not be reflected in cell performances.

The necessity to take into consideration the angular size of the x-ray beam and its influence on the parameters of the reflected x-ray beam for ray tracing analysis will be shown.

Parabolic graded multilayer mirrors used as condensing optics increase the intensity throughput of laboratory high-resolution XRD systems. The x-ray source size and the figure error must be considered in real systems. An expression given by Gutman and Verman can be used to estimate source size effects. Recent measurements show the improvement of the mirror fabrication with respect to figure errors. The errata given in this paper corrects a `factor of two error' which appeared in our original paper.

Domain inversion in an (001) section of flux-grown has been produced by applying an electric field to a sample via liquid electrodes. An x-ray anomalous scattering experiment has been used for characterization of the domain reversal. The variation of the diffraction images of inversion domains revealed via anomalous-scattering topography clearly indicates that near-perfect inversion domains have been formed by electric-field poling.

The optimum double-coded Hadamard transform spectroscope consists of a vertical and horizontal dispersion system plus two one-dimensional (1D) masks. The horizontal dispersion system plus a 1D mask can be replaced by a 2D Hadamard mask, resulting in a more practical design.