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This study describes important techniques for production of a series of video signals for use in fine focusing operations and near-perfect astigmatism correction in the general-purpose scanning electron microscopy (SEM) field. These techniques can enhance the stability of the signal greatly when used for focusing. As two particularly important fundamental techniques, SEM image acquisition with priority given to the signal-to-noise ratio and signal reinforcement based on the active image processing concept were utilized fully. The performance improvement was evaluated using the case of a previously reported support system for fine focusing and astigmatism correction based on image covariance. The method is almost completely robust against noise within practical limits and allows for focusing and astigmatism correction for even extremely noisy SEM images. The results of this study may be useful not only in the SEM field but also in many fields that use weak signals.

A correlation coefficient is often used as a measure of the strength of a linear relationship (i.e., the degree of similarity) between two sets of data in a variety of fields. However, in the field of scanning electron microscopy (SEM), it is frequently difficult to properly use the correlation coefficient because SEM images generally include severe noise, which affects the measurement of this coefficient. The current study describes a method of obtaining a correlation coefficient that is unaffected by SEM noise in principle. This correlation coefficient is obtained from a total of four SEM images, comprising two sets of two images with identical views, by calculating several covariance values. Numerical experiments confirm that the measured correlation coefficients obtained using the proposed method for noisy images are equal to those for noise-free images. Furthermore, the present method can be combined with a highly accurate and noise-robust position alignment as needed. As one application, we show that it is possible to immediately examine the degree of specimen damage due to electron beam irradiation during a certain SEM observation, which has been difficult until now.

This study proposes an efficient and fast method of scanning (e.g., television (TV) scan) coupled with digital image processing technology to replace the conventional slow-scan mode as a standard model of acquisition for general-purpose scanning electron microscopy (SEM). SEM images obtained using the proposed method had the same quality in terms of sharpness and noise as slow-scan images, and it was able to suppress the adverse effects of charging in a full-vacuum condition, which is a challenging problem in this area. Two problems needed to be solved in designing the proposed method. One was suitable compensation in image quality using the inverse filter based on characteristics of the frequency of a TV-scan image, and the other to devise an accurate technique of image integration (noise suppression), the position alignment of which is robust against noise. This involved using the image montage technique and estimating the number of images needed for the integration. The final result of our TV-scan mode was compared with the slow-scan image as well as the conventional TV-scan image.

The current study describes a new support system for fine focusing and near-perfect astigmatism correction for scanning electron microscopy (SEM). The signal-to-noise ratio of a series of SEM images obtained from fast scan rates (TV scan) was adopted as a new metric for evaluating focus. Measured signal-to-noise ratio values were converted to an acoustic signal (sound wave frequency) using digital image processing techniques, enabling the SEM user to evaluate image focus using the auditory modality. Accurate focusing and correcting astigmatism in general-purpose SEM is traditionally time-consuming and difficult. The proposed system may substantially reduce the required operation time for fine focusing. Moreover, the system is relatively immune to noise, successfully supporting focus and astigmatism correction with very noisy SEM images. Our proposed focus support system may be helpful for general-purpose SEM observation of a variety of specimens under a wide range of operating conditions.

In order to improve the critical current density ( J c ) and mechanical property of Bi-2223 sintered bulk, Ni wire meshes were added in the bulk. For fabricating large-sized cylindrical Bi-2223/Ni meshes composite, composing meshes are easy to produce compared with adding a lot of wires. The mesh concentration was 18 × 18 meshes/cm 2 using Ni wires of 0.25 mm in diameter. The Ni meshes were plated with Ag by 0.03 mm in thickness. We prepared the cylindrical sintered bulk for a current lead, 32 mm in outer diameter, 2 mm in thickness and 110 mm in length using a cold isostatic pressing (CIP) method. The samples were sintered at 845 °C for 50 h. After treatment again with CIP as an intermediate pressing, the samples were re-sintered. Small species were cut from the cylinder for measurement of critical current density ( J c ) at 77 K under self-field. There existed higher J c portions and low J c portions in the composite cylinder. Scanning electron microscope (SEM) observation showed that highly c -axis oriented and densely structured Bi-2223 plate-like grains could be formed around the interfacial region between the superconducting oxide and the Ag-plated Ni wires. There observed structural dislocation, which lead to low J c portions in the cylinder.

In order to improve the superconducting property and mechanical property of Bi- 2223 sintered bulk, Ni wire meshes were added in the bulk. The mesh concentration was 18 × 18 meshes/cm2 using Ni wires of 0.25 mm in diameter. The Ni meshes were plated with Ag by 0.03 mm in thickness. We prepared the cylindrical sintered bulk, 27 mm in outer diameter 2 mm in thickness and 50 mm in length using a cold isostatic pressing (CIP) method. The samples were sintered at 845 °C for 50 h. Critical current density (Jc) of the samples was estimated at 77 K under self-field. By composing with the Ni meshes the Jc property was improved compared with the samples without the mesh. It is mentioned that the Jc increase of the Bi-2223 bulk by adding with the Ni meshes is attributed from formation of the Bi-2223 plate-like grains in the vicinity of the Ag-plated Ni wires.

This is an attempt to explore feasibility to develop an open gradient magnetic separator for mixed powder under dry condition. The magnetic separator proposed here is intended to separate the ferromagnetic particles from mixed powder, being based on the consideration that the separation efficiency depends upon changing systematically the particle sizes and its surface properties such as hydrophobicity and cohesive force. As a result, it is found that the separation efficiency became lower as the particle size of the mixed particles became smaller. This is supposed to be caused by the cohesive force between the particles of ferrite and alumina which are easily affected by the magnetic drag force and the gravity difference. But the result is encouraging because the separation efficiency will be enhanced if the magnetic gradient is increased and if air flow in the separator is optimized in the appropriate system of the open-gradient magnetic separator proposed in this paper.

We evaluated the superconducting properties of DyBa 2 Cu 3 O x (Dy123) with different amounts of Dy 2 BaCuO 5 (Dy211) phase. The samples were melt-textured DyBaCuO superconductors, which were made from the mixtures in molar ratios of Dy123:Dy211=1: x ( x =0.03, 0.05, 0.08 and 0.1). The temperature dependence of resistance of DyBaCuO superconductors on different amounts of 211 phase was measured. The data of fluctuation amplitude and the dimension of conduction were obtained from analyzing the fluctuation. The results show that coherence length obtained from this analysis becomes larger as amounts of 211 phase increase. The evidence is found that the pinning force in the sample is well correlated with the characteristic length of superconductivity.

It is known that critical current density Jc in Bi-Based superconductors increases with the length of sintering time, and further increases with cold isostatic pressing (CIP) process. Analysis of excess conductivity due to the thermal fluctuation above Tc provides information about fluctuation amplitude and the dimensionality of conduction, and makes it possible to evaluate the superconducting correlation length. In this study, the mechanism of how Jc of Bi-based copper oxide improves by increasing sintering time is discussed on the basis of fluctuation-conductivity analysis. The temperature dependence of the resistance of Bi-based superconductors with various sintering time was measured. It was found that correlation length and effective cross-sectional area obtained from analysis systematically decrease with the sintering time, and that these parameters correlate well with Jc of the samples. It is widely accepted that the increase in Jc of the samples is due to the improvement in the crystallinity, (i.e., the increase in crystal density and better alignment of the crystal grains) which brings about decrease in correlation length and effective cross-sectional area. Therefore, the effect of the improvement in the density and alignment of the crystals, an important factor for increasing critical current density, was evaluated from the fluctuation conductivity analysis.

Laminated bulk samples consisting of alternate layers of Bi-2223 and Ag were prepared to improve the Jc of sintered Bi-2223 plate samples. Two to seven Ag sheets were inserted between six plate samples and the difference in the impedance between two sets of detecting coils was vectorially measured at 10 kHz in the temperature range of 77.3–120 K by the simultaneous resistivity and magnetic penetration depth measurement (SRPM) method. The difference in the impedance was analyzed by treating it as a serial circuit having resistance Rs and inductance Ls. It was clarified that as the number of Ag sheets is increased, Jc and the quality factor Q (=ωLs/Rs) increase in proportion, where ω is the angular frequency.

We devised a new field-of-view autotracking method for online tomography reconstruction based on a cross-correlation between a pair of neighbours, called back-projected ray images, among a specimen tilt sequence. One ray image is calculated through normal filtered back-projection only in the cross-sectional plane from each projection image. This ray-image matching can reliably track the field-of-view because a pair of neighbouring ray images mostly cross-correlates at the existing three-dimensional object position. Online experiments using real specimens resulted in successful autotracking performance with high accuracy, and online tomograms were obtained immediately after the final tracking at the last tilting angle.

The J c of a sintered Bi-2223/Ag multi-layered bulk sample increases as the number of Ag layers is increased. The sample used in this experiment was placed next to the bifilarly wound coil consisting of two coils having the same properties located at the same place. With the sample fixed, a current was applied to the two coils in the same and then in the opposite direction so as the fluxes augment or counteract each other, and the difference in the synthetic impedance of the two coils ( ΔZ ) was measured. First, the temperature dependence of ΔZ for Ag and Bi-2223 samples, and Bi-2223/Ag multi-layered sample pellets were measured at 10 kHz. Next, each sample was treated as a serial circuit having the same resistance and inductance, and a formula for obtaining ΔZ for each bifilarly wound coil was derived. The calculated values of the temperature dependence of ΔZ obtained by substituting the sample and coil constants into the formula corresponded fairly well with the measured ones.

/spl Delta/Z (the difference in the impedance of a solenoid coil with and without a superconductive sample) of 0, 10, 20 and 30 wt% Ag-doped YBaCuO (c-axis oriented) and a Bi-based sintered sample were measured by the SRPM method between 200 Hz and 1 MHz at room temperature and liquid N/sub 2/ temperatures. At room temperature, frequency dependence of /spl Delta/Z was observed in both samples. These dependencies were analyzed using a serial circuit having the same resistance and inductance as the samples by which the existence of /spl Delta/Z was confirmed. Below T/sub c/, only /spl Delta/Z of a Bi-based sample was measured between 200 Hz and 1 MHz. /spl Delta/R (the real part of /spl Delta/Z) was evaluated as a function of frequency(f). /spl Delta/R from 0.25 to 1 kHz is assumed to be proportional to f/sup 2/ (normal skin effect). /spl Delta/R from 1 kHz to 50 kHz is proportional to f/sup 5/3/ (anomalous skin effect). /spl Delta/R from 50 kHz to 700 kHz is proportional to f/sup 2/3/ (anomalous skin effect). It was found that /spl Delta/R between 1 kHz and 700 kHz agrees with the property obtained by the equation confirming that it is in the region of anomalous skin effect.

Basic theoretical analyses to detect undesirable foreign metal pieces in the meat being processed have already been carried out. In this study, taking the low conductivity of meat into account, a double-layered spherical sample structure which enables easy analyses was selected. In order to detect these conductive materials, analyses of the difference in the impedance of a circular coil with, and another one without, a double-layered spherical conductor were made. In this way, a new formula for obtaining the electromagnetic properties of a double-layered spherical sample was derived. The process of deriving the new formula is explained. The calculated value was compared with the experimental value. Their values had a close correlation.

A method using a solenoid coil for simultaneously estimating the electric and magnetic properties of a spherical conductor was studied. These properties are estimated by finding the difference in the complex impedance of the coil with and without a sample to find out the measuring value that best coincides with the theoretical value. A new formula applicable to a nonmagnetic, a magnetic or a superconductive spherical sample was derived. The conductivities a and permeabilities /spl mu/ measured by this method and by the conventional methods were compared using various samples. The deviations were no larger than 3% for a nonmagnetic samples, and 1.5% for /spl mu/ of magnetic samples.

An attempt to develop a method to simultaneously estimate both the resistivity /spl rho/ and the magnetic penetration depth /spl lambda/ by vectorially measuring the difference in the impedance between two circular solenoid coils, one with and the other without a cylindrical superconductor, has been made. It was ascertained that the regions of normal and anomalous skin effect can be defined from the frequency dependence of the difference in the impedance between the two coils. The mean free path of electrons l is evaluated by applying the frequency dependence of the difference in the impedance of the coils to the anomalous skin effect region. The values of /spl rho/, /spl lambda/ and l of Bi-based sintered bulks with different J/sub c/ were evaluated at liquid N/sub 2/ temperature.

The quality of the image signal obtained from the environmental secondary electron detector (ESED) employed in a variable pressure (VP) SEM can be dramatically improved by using helium gas. The signal-to-noise ratio (SNR) increases gradually in the range of the pressures that can be used in our modified SEM. This method is especially useful in low-voltage VP SEM as well as in a variety of SEM operating conditions, because helium gas can more or less maintain the amount of unscattered primary electrons. In order to measure the SNR precisely, a digital scan generator system for obtaining two images with identical views is employed as a precondition. SCANNING 29: 225-229, 2007. © 2007 Wiley Periodicals, Inc.

HoSb and DySb compounds have a very high specific heat peak below 10 K, and the measured specific heat of GdSb has a distinct peak at 25 K. Analyses have been conducted focused on the magnetic properties of these compounds to understand the difference between samples with sharp specific heat peaks and those with broad peaks. The magnetization of the samples was measured with a Vibrating Sample Magnetometer (VSM). The magnetic properties of HoSb and DySb are small above 100 K, while the magnetic property of GdSb exists up to near room temperature. Although further analysis is necessary, the data suggest that the differences in the specific heats between the materials is mainly due to differences in their magnetic properties.

To survey the local superconductivity and cracks in a large superconductor, a method for estimating the property from the difference in the real component /spl Delta/R and imaginary component /spl Delta/X of the complex impedance of a coil with a sample and another without one is proposed. This method was applied to two samples one which was superconductive and one not superconductive at 77.3 K. It is understood that samples become superconductive when /spl Delta/R is sufficiently near 0 and /spl Delta/X is negative. The relation between two superconductors, one without and the other with artificially induced cracks was experimentally investigated. It was confirmed that the property of the sample with cracks deviated from superconductivity. As for a superconductive cylinder of 0.5 m in diameter and 1 m in length open at one end, /spl Delta/R and /spl Delta/X at various points on the wall and at the closed end were measured at 77.3 K and the values of /spl Delta/R were sufficiently near 0. All values of /spl Delta/X were negative. The magnetic shielding effect was confirmed to be 1/20000.

Basic theoretical analyses to detect undesirable foreign metal pieces in the meat being processed have already been carried out. In this study, taking the low conductivity of meat into account, a double-layered spherical sample structure which enables easy analyses was selected. In order to detect these conductive materials, analyses of the difference in the impedance of a circular coil with, and another one without a double-layered spherical conductor were made. In this way, a new formula for obtaining the electromagnetic properties of a double-layered spherical sample was derived. The process of deriving the new formula is explained. The calculated value was compared with the experimental value. Their values had a close correlation.

We have been studying a method for simultaneously measuring the electrical and magnetic properties of spherical sample (SRPM method). In the SRPM method, the differences in the impedance of a circular coil with a sample and an identical one without a sample are vectorially measured, and the values are compared with the one calculated by the formulae including the sample parameters. Then the properties are simultaneously estimated by finding their agreements. As the sample is inserted into the coil and pulled out of the coil alternately, the properties obtained by this method often contain the large error caused by the deviation from ideal condition of the position the sample and the coil. For the improvement of such situation, a method using double coils is proposed. The spherical sample is coaxially placed on the center of both coils, and the connections of the two coils can be switched to pass the current through the coils in the same direction or in opposite directions. A new formulae for obtaining the difference in the impedance of the coil is derived to apply to such conditions. In order to confirm the validity of these formulae, the conductivity estimated by the SRPM method and the DC four-probe method were compared. They are within 1.8%.

Metal detectors are extensively used to find undesirable metal objects in processed food. In such a typical metal detector, the coils are coaxially arranged with the transmitting coil in the center and two receiving coils on the sides. The receiving coils are connected to a differential amplifier. When the magnetic field generated in the transmitting coil is disturbed by metal objects, the amplitude and phase of the output voltage of the differential amplifier change and thus the existence of foreign metal pieces are detected. The relationship between the amplitude and phase of the output and the electromagnetic properties of the metal objects, however, has only been discussed experimentally so far. The authors have already developed the SRPM method to simultaneously estimate the electrical and magnetic properties of a spherical sample by vectorially measuring the difference in the impedance of two circular solenoid coils, one with and the other without a sample. An attempt is made to theoretically analyze the properties, such as size, conductivity and permeability of the metal objects from the output, i.e., amplitude and phase of the metal detector. Based on this method an equation to estimate the vector voltage induced in the receiving coil by the metal object is derived by using a spherical sample to simplify the analysis. The validity of the new formula was confirmed by experiments using iron, aluminum and SUS304 objects.

In order to simultaneously evaluate the resistivity (/spl rho/) and the magnetic penetration depth (/spl lambda/) of a flat plate superconductor, a method using a bifilar winding coil is proposed. The bifilar winding coil, which has the same properties, consists of two coils located at same place. When a current is applied in the same or opposite direction with the sample fixed, the magnetic fluxes augment or counteract each other. The difference in the synthetic impedance of the two coils in the above cases corresponds to the cases when there is a sample or no sample in the conventional method (SRPM method). This difference is compared with the values calculated for /spl rho/ and /spl lambda/ as parameters to estimate the experimental values of /spl rho/ and /spl lambda/. For a Bi pellet superconductor, /spl rho/ and /spl lambda/ were simultaneously estimated at 10 kHz. The values of /spl rho/ and /spl lambda/ at 77.3 K was 4.2/spl times//sup -11/ /spl Omega/m and 20.4 /spl mu/m, respectively. This method, which does not electrically touch the sample, is superior to the conventional method for measuring very low resistivity.

Materials including rare-earth and Sb compounds were developed as regenerator materials for a 4K GM refrigerator. Sb compounds have a remarkably large peak value of specific heat in the low temperature range. First, the heat capacities, thermal conductivity, and thermal expansion of HoSb, DySb and GdSb, which are anti-ferromagnetic with a large spin value in the low temperature range, were measured. Then, the results of these measurements were used to analyze the problems encountered when Sb compounds were used as the regenerative materials in a GM refrigerator.

Bi-2223 is suitable to be applied under low field and near liquid nitrogen temperature. Jc value of the bulk materials is much smaller than that of the wire and tape materials. This should limit application field of the bulk. Then, we tried to improve Jc properties of Bi-2223 bulk by inserting Ag sheets into oxide. It was found that Jc values of the multi-layered bulk were improved in proportional to the number of Ag sheets. We investigated the microstructure of the Bi-2223/Ag multi-layered bulk. As a result, good alignment and dense structure of the oxide phase was observed near the interface between Bi-2223 layer and Ag sheet.

To obtain the large value of Jc, it is important to find the optimal sintering time of Bi-2223 bulk. Then, to analyze the electromagnetic properties of Bi-2223 sintered bulk, pellet samples were made by varying the sintering time and the number of Cold Isostatic Press (CIP). The properties of their samples were mainly measured by the SRPM method which could evaluate the values related to the surface impedance of samples within the frequency band of kHz from MHz. In this paper, the temperature dependence of the real part of the difference in the coil impedance was especially focused. The best conditions of the sintering time and number of CIP were investigated by SRPM method, and the results were reported.

The properties of the Bi-based sintered bulks having different number of the iteration of CIP and different sintering time were measured by the SRPM method and the complex susceptance method. It has been obviously shown by measuring these samples that the difference in the impedance of the coil by the SRPM(Simultaneous Resistivity and magnetic Penetration depth Measurement) method corresponds to the complex susceptibility. The measurement at high frequency by the SRPM method is available as a powerful tool for detecting the different superconductive phases in the sample.

The difference in the impedance of a coil with and without a sample of Ag-doped YBaCuO superconductor was vectrially measured between the frequencies of lOOkHz and lOMHz. The frequency dependence of the difference in the impedance above T c was analyzed, and it was found out that the frequency dependence increased in proportion to the amount of Ag and to the decrease in resistivity.