bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Super-High-Resolution HVEM (H-1500) Newly Installed in NIRIM
Authors: Horiuchi S. , Matsui Y. 
Published: June 2020

A new high-voltage electron microscope (H-1500) specially aiming at super-high-resolution (1.0 Å point-to-point resolution) is now installed in National Institute for Research in Inorganic Materials ( NIRIM ), in collaboration with Hitachi Ltd. The national budget of about 1 billion yen including that for a new building has been spent for the construction in the last two years (1988-1989). Here we introduce some essential characteristics of the microscope.(1) According to the analysis on the magnetic field in an electron lens, based on the finite-element-method, the spherical as well as chromatic aberration coefficients ( Cs and Cc ). which enables us to reach the resolving power of 1.0Å. have been estimated as a function of the accelerating As a result of the calculaton. it was noted that more than 1250 kV is needed even when we apply the highest level of the technology and materials available at present. On the other hand, we must consider the protection against the leakage of X-ray. We have then decided to set the conventional accelerating voltage at 1300 kV. However. the maximum accessible voltage is 1500 kV, which is practically important to realize higher voltage stabillity. At 1300 kV it is expected that Cs= 1.7 mm and Cc=3.4 mm with the attachment of the specimen holder, which tilts bi-axially in an angle of 35° ( Fig.1 ). In order to minimize the value of Cc a small tank is additionally placed inside the generator tank, which must serve to seal the magnetic field around the acceleration tube. An electron gun with LaB6 tip is used.
Computer Image and Spectrum Acquisition on an HB501A STEM
Authors: Kirkland Earl J. 
Published: June 2020

A DEC VAXstation 3200 color graphics computer workstation has been interfaced to a Vacuum Generators HB501A Scanning Transmission Electron Microscope (STEM) for on-line image and spectrum acquisition. Electron Energy Loss Spectra (EELS) or Auger spectra may be recorded (serially) using pulse or analog modes (using the voltage to frequency converters supplied by VG). High resolution bright field (BF) / annular dark field (ADF) image pairs may be recorded simultaneously as well as simultaneous pairs of Auger / secondary images. A resolution of 2Å (or better) has been achieved with an experimental pole piece (Cs = 1.2mm. and 0.7mm.). The image quality obtained with this system is greatly improved over the Polaroid system supplied with the microscope.A schematic of the overall system is shown in FIG 1. To avoid possible ground loop noise the entire computer system has been optically isolated from the STEM. There are four 16 bit digital to analog converters (DAC) for controlling the x,y position, the EELS energy and the Auger energy. The output of four detectors is connected back to the computer for pulse counting using a Qbus board manufactured by Codar Technologies. This board has three AMD 9513 counter IC's (with five 16 bit counters each) to count the electron or VFC pulses. The EELS spectra are acquired using two 32 bit counters (16 bit counters concatenated) and may function in a constant dwell time or constant count (constant signal to noise ratio) mode. The Auger and BF/ADF image counters work in a constant dwell time 16 bit mode. The average CPU overhead has been measured at 50 microsec per point in polled mode (images) and 500 microsec in interrupt driven mode (spectra).
Improvement of Stem Images by Means of Elimination of Influence of Statistical Fluctuation in Incident Electrons
Authors: Michio Hibino , Suzuki Takahiro , Hanai Takaaki , Maruse Susumu 
Published: June 2020

The noise, due to statistical fluctuation of signal electrons, determines the ultimate resolution limit of imaging and analysis. The signal electrons (N) for each pixel are formed through two stages of statistical processes; Poisson distribution for the number of incident electrons (No) and polynomial distribution for forming signal electrons. The signal electrons therefore obey the Poisson distribution of average nOp (no:average of incident electrons, p:probability of forming signal electrons) and of standard deviation . In order to improve the resolution limit set by the statistical noise of signal electrons, a new method of normalization is proposed for STEM.In STEM imaging of thin specimens, the total transmitted electrons correspond to the incident electrons. It is therefore possible to know the incident electrons by summing up all the transmitted electrons and to normalize the signal electrons by incident electrons, for eliminating the influence of fluctuations of incident electrons. The average E and the standard deviation σ of normalized signal electrons are expressed by p and , respectively, for no> > 1 , indicating that E/σ value is improved by a factor of .
Sensitive High-Vacuum Monitoring for Philips Electron Microscopes Which Employ ION Getter Pumping
Authors: Greene Alexander. E. 
Published: June 2020

A very sensitive vacuum monitor may be easily and inexpensively added to any Philips CM or 400 series electron microscope. This digital, auto-ranging volt meter will also operate as an excellent leak detector.The newer Philips computerized transmission electron microscopes have no separate high vacuum gauge and sense high vacuum the same way as it is done on the 400 series instruments. The high vacuum monitoring technique for these microscopes is accomplished by relating the electrical current required by the Ion Getter Pump to the quality of the vacuum (i.e. the better the vacuum, the lower the current). The system for vacuum monitoring measures the voltage across a low value resistor which is placed in series with the Getter Pump and the pump power supply and is usually located near ground or earth potential. The power supply delivers about 7000 V.D.C. to the pump and the voltage across the low value resistor is proportional to the current being drawn by the pump. This voltage is measured, amplified and then compressed by a logarithmic amplifier so one meter scale or a simple digital-to-analog converter can provide a reading equivalent to the high vacuum value. Because of the logarithmic amplifier, small changes cannot be seen; only the general vacuum quality can be monitored.
Point-Cathode Electron Gun Using Electron-Beam Bombardment for Cathode Tip Heating
Authors: Iiyoshi Ryo , Maruse Susumu , Takematsu Hideo 
Published: June 2020

Point cathode electron gun with high brightness and long cathode life has been developed. In this gun, a straightened tungsten wire is used as the point cathode, and the tip is locally heated to higher temperatures by electron beam bombardment. The high brightness operation and some findings on the local heating are presented.Gun construction is shown in Fig.l. Small heater assembly (annular electron gun: 5 keV, 1 mA) is set inside the Wehnelt electrode. The heater provides a disk-shaped bombarding electron beam focusing onto the cathode tip. The cathode is the tungsten wire of 0.1 mm in diameter. The tip temperature is raised to the melting point (3,650 K) at the beam power of 5 W, without any serious problem of secondary electrons for the gun operation. Figure 2 shows the cathode after a long time operation at high temperatures, or high brightnesses. Evaporation occurs at the tip, and the tip part retains a conical shape. The cathode can be used for a long period of time. The tip apex keeps the radius of curvature of 0.4 μm at 3,000 K and 0.3 μm at 3,200 K. The gun provides the stable beam up to the brightness of 6.4×106 A/cm2sr (3,150 K) at the accelerating voltage of 50 kV. At 3.4×l06 A/cm2sr (3,040 K), the tip recedes at a slow rate (26 μm/h), so that the effect can be offset by adjusting the Wehnelt bias voltage. The tip temperature is decreased as the tip moves out from the original position, but it can be kept at constant by increasing the bombarding beam power. This way of operation is possible for 10 h. A stepwise movement of the cathode is enough for the subsequent operation. Higher brightness operations with the rapid receding rates of the tip may be improved by a continuous movement of the wire cathode during the operations. Figure 3 shows the relation between the beam brightness, the tip receding rate by evaporation (αis the half-angle of the tip cone), and the cathode life per unit length, as a function of the cathode temperature. The working life of the point cathode is greatly improved by the local heating.
Toward The Simultaneous Correction of Spherical and Chromatic Aberration in Electron Optics by Means of an Electrostatic Electron Mirror
Authors: Rempfer Gertrude. F. 
Published: June 2020

Optimum performance in electron and ion imaging instruments, such as electron microscopes and probe-forming instruments, in most cases depends on a compromise either between imaging errors due to spherical and chromatic aberrations and the diffraction error or between the imaging errors and the current in the image. These compromises result in the use of very small angular apertures. Reducing the spherical and chromatic aberration coefficients would permit the use of larger apertures with resulting improved performance, granted that other problems such as incorrect operation of the instrument or spurious disturbances do not interfere. One approach to correcting aberrations which has been investigated extensively is through the use of multipole electric and magnetic fields. Another approach involves the use of foil windows. However, a practical system for correcting spherical and chromatic aberration is not yet available.Our approach to correction of spherical and chromatic aberration makes use of an electrostatic electron mirror. Early studies of the properties of electron mirrors were done by Recknagel. More recently my colleagues and I have studied the properties of the hyperbolic electron mirror as a function of the ratio of accelerating voltage to mirror voltage. The spherical and chromatic aberration coefficients of the mirror are of opposite sign (overcorrected) from those of electron lenses (undercorrected). This important property invites one to find a way to incorporate a correcting mirror in an electron microscope. Unfortunately, the parts of the beam heading toward and away from the mirror must be separated. A transverse magnetic field can separate the beams, but in general the deflection aberrations degrade the image. The key to avoiding the detrimental effects of deflection aberrations is to have deflections take place at image planes. Our separating system is shown in Fig. 1. Deflections take place at the separating magnet and also at two additional magnetic deflectors. The uncorrected magnified image formed by the objective lens is focused in the first deflector, and relay lenses transfer the image to the separating magnet. The interface lens and the hyperbolic mirror acting in zoom fashion return the corrected image to the separating magnet, and the second set of relay lenses transfers the image to the final deflector, where the beam is deflected onto the projection axis.
Observation of Single Magnetic-Flux Quanta Using Electron Holography
Authors: Matsuda T. , Hasegawa S. , Endo J. , Osakabe N. , Tonomura A. , Aoki R. 
Published: June 2020

A Magnetic flux quantum (fluxon) penetrating a superconductor plays an important role in both fundamental and practical applications of superconductivity. However, the fluxon has evaded direct observation, because it is shaped like an extremely thin filament in addition to its small flux value, h/2e (=2x10−15Wb). Several methods have already been developed to indirectly observe each filament of flux. One method is Bitter's [1], in which magnetic powder is sprinkled on the superconductor surface. The powder accumulates at the fluxons, and the image is observed by electron microscopy.We have observed the magnetic field of a single fluxon using holographic electron interferometry [2], in which the phase distribution of an electron beam can be measured to a precision of 2Π/50. The schematic diagram of the experiment is shown in Fig. 1. A weak magnetic field is applied perpendicularly to a superconducting lead film. Fiuxons penetrating the film are observed as phase contour fringes through the electron holography process. The sample is prepared by evaporating lead on one side of a thin tungsten wire, which is shown in Fig. 2.
Advances in Photoelectron Imaging
Authors: Griffith O. Hayes , Birrell G. Bruce , Habliston Douglas H. , Hedberg Karen K. 
Published: June 2020

There are many possible strategies of photoelectron imaging. The common theme is to form the image with electrons that have been photoejected from a surface by UV light (i.e. the photoelectric effect). Currently the highest resolution method is photoelectron microscopy (PEM), which is also called photoemission electron microscopy (PEEM). This approach has its roots in the early developments in electron microscopy in Germany. However, modern ultra high vacuum technology and image enhancement techniques have made possible significant advances in the capabilities of photoelectron imaging.Photoelectron microscopy is the electron optical analog of fluorescence microscopy. Light is focused on a specimen and the emitted electrons are accelerated, and the image magnified by means of an electron optical system. The main advantage of photoelectron microscopy is the source of contrast. Small differences in the bonding of outermost electrons can cause significant contrast between molecules that would be otherwise difficult to detect. Biological systems are rich in macromolecules that differ in molecular ionization potentials and this source of information remains largely unexplored.
Development of A 350-KV Holography Electron Microscope and its Applications
Authors: Kawasaki Takeshi , Endo Junji , Matsuda Tsuyoshi , Tonomura Akira 
Published: June 2020

The 350 kV field-emission electron microscope shown in Fig.1 has been developed to widen the applications of electron holography. A field emission beam is used because it is very bright at first and monochromatic. However, its brightness deteriorates while passing through accelerating electrodes and condenser lenses because of their spherical and chromatic aberrations. A magnetic lens is installed just below a (310)-oriented tungsten tip. A magnetic lens is used so that the electron source image can be located at the most favorable position between the accelerating tube and the first condenser lens to minimize the aberrations and to increase brightness. The measured brightness (probe current) ranges from 1.4x109A/cm2/sr (0.37 nA) to 6.7x108A/cm2/sr (2.2 nA) with 10 μA total emission current at 300 kV.These increased brightness and narrow energy spread of the electron beam enable observing fine spacing lattice fringes in a gold thin film. Lattice fringes of 0.065 nm spacing were actually observed in the electron micrograph shown in Fig. 2. The incident electron beam was along the [001] axis, and the (400) andreflected beams were used to form the fringes. A 0.055 nm spacing lattice image is shown in Fig. 3. These fringes resulted from the interference of the electron beam, with an incident axis from the [111] direction into the gold thin film, by theanddiffracted beams. This spacing is the shortest observed to date.
Visualisation and Quantitative Evaluation of Small Thickness and Phase Steps from Electron Holograms by Digital Image Processing
Authors: Lauer Rolf , George Ade 
Published: June 2020

Digital image processing proved to be highly suited for the quantitative decoding of the phase information stored in off-axis electron holograms [1]. We want to show here that digital processing is superiour to light optical reconstruction work because of its flexibility and extended possibilities; i.e. phases and amplitudes can be displayed directly, in contrast to modulated intensity patterns in the light optical case. When a hologram is stored digitally, no further optical or photographical processing is necessary. The reconstruction can be done interactively within seconds by means of an image processor with Fast Fourier Transform hardware [2]. We give here some examples:(1) A flat MgO crystal which has been thinned by electron bombardment [3]. Fig.1a is a micrograph, copied on hard paper, where a quadratic deepening becomes just visible. Fig.1b is an off-axis hologram of this area. By light-optical interferometric reconstruction using the second diffraction order of the hologram, the contour map of Fig.1c has been obtained. Figs.1d,e are digital reconstructions where eight lines of equal phase correspond to a phase shift of 2π. This has been achieved with the method described by Ade and Lauer (these Proceedings). The shift d of the fringes corresponds to a height difference of 2.2nm. Fig.If is a superposition of Figs.1d,e giving a topographic view which reveals even smaller thickness variations.
Digital Phase Amplification in Electron off-Axis Holography
Authors: Ade George , Lauer Rolf 
Published: June 2020

An off-axis hologram is obtained by recording the interference pattern resulting from the superposition of the object wave and a slightly tilted reference wave. The phase distribution of the object wave is a function of several parameters such as the electromagnetic potentials, the accelerating voltage of the electrons, and the object thickness. Therefore, the electromagnetic fields and the thickness of the object can be directly deduced from the phase distribution stored in the hologram.This distribution is usually determined by light optical interferometric reconstruction of the hologram using one or two diffracted beams. If the two first order beams are utilized, a two-times phase-amplified interference image is obtained. The sensitivity of phase detection can generally be enhanced if higher diffraction orders are used. Two methods have been successfully applied for this purpose. In the first method [1], the high order beams are obtained by making a hard photographic copy of the original hologram. In the second technique [2-4], a new hologram is formed from the original one by emloying the two first order diffracted beams. The new hologram is photographically recorded on a film, and the film is bleached in order to enhance the diffraction efficiency. When this procedure is repeated n times, an amplification rate of 2n is achieved.
Three-dimensional Image Analysis of Tubular Crystals of Membrane Proteins in Ice
Authors: Toyoshima Chikashi 
Published: June 2020

Frozen-hydrated electron microscopy is a powerful method that allows us to preserve biological macromolecules in physiological ionic conditions and obtain the density (Coulomb potential) maps directly. Changes in quarternary structure in different conditions have been demonstrated using this technique for the gap junction (1) and the nicotinic acetylcholine receptor (2). Since the image contrast originates from the difference in density between the specimen and ice, the method has a considerable advantage over conventional methods in resolving structure inside the lipid bilayer, especially when molecules are arranged in a helical array to form tubular crystals. The molecules in a helical array present many different views to the incident electron beam, hence the electron micrograph actually contains a large amount of three-dimensional information. By using helical image analysis, it is possible to obtain a three-dimensional image from a single micrograph in many instances. Furthermore, the data is complete: There is no "missing cone" problem arising from a limited angle of tilt; the resolution in the reconstructed image is isotropic. The mean (radial) density distribution is available from equatorial data; thus the value in the map is an absolute measure of the density.We have been analysing tubular crystals of the nicotinic acetylcholine receptor from electric ray and the calcium ATPase from rabbit sarcoplasmic reticulum. Helical image analysis at 17 Å resolution of the narrow tubes embedded in ice has allowed two leaflets of the lipid bilayer to be resolved clearly (2). The lipid bilayer was not resolved in previous tilt reconstructions using flattened tubes at a similar (in plane) resolution and up to 60 degrees tilt (3).
Imaging Molecules and Cells with the Atomic Force Microscope
Authors: Prater C.B. , Weisenhorn A.L. , Northern B. Dixon , Peterson C.M. , Gould S.A.C. , Hansma P.K. 
Published: June 2020

The atomic force microscope (AFM) gives topographic images by scanning a sharp stylus over a surface. The stylus is attached to a spring lever which is deflected when the stylus interacts with the surface. The AFM images a surface by measuring deflection as a function of position over the surface. The AFM has given atomic resolution images of both conductors and nonconductors. The AFM has also given images of amino acid polymers with subnanometer resolution. The AFM has imaged samples covered with a liquid and biological processes like blood clotting have been imaged. In this report we present several images that demonstrate the variety of samples that can be imaged with the AFM.The AFM has imaged adsorbed molecules at subnanometer resolution. Figure 1A is an image of the bare (010) surface of the natural zeolite, clinoptilolite. Molecules of t-butanol were then adsorbed onto the surface from the liquid and the sample was imaged again (Fig. IB).Figure 2 is an image of double stranded DNA dried onto mica. The resolution is sufficient to reveal corrugation due to the major groove of the double helix. We are currently working to gain resolution sufficient to sequence single-stranded DNA.
Three-Dimensional Reconstruction of Two Forms of the Chaperonin GRO EL
Authors: Carrascosa J.L. , Abella G. , Marco S. , Muyal M. , Carazo J.M. 
Published: June 2020

Chaperonins are a class of proteins characterized by their role as morphogenetic factors. They trantsiently interact with the structural components of certain biological aggregates (viruses, enzymes etc), promoting their correct folding, assembly and, eventually transport. The groEL factor from E. coli is a conspicuous member of the chaperonins, as it promotes the assembly and morphogenesis of bacterial oligomers and/viral structures.We have studied groEL-like factors from two different bacteria:E. coli and B.subtilis. These factors share common morphological features , showing two different views: one is 6-fold, while the other shows 7 morphological units. There is also a correlation between the presence of a dominant 6-fold view and the fact of both bacteria been grown at low temperature (32°C), while the 7-fold is the main view at higher temperatures (42°C). As the two-dimensional projections of groEL were difficult to interprete, we studied their three-dimensional reconstruction by the random conical tilt series method from negatively stained particles.