MEETINGS AND CONFERENCES

ELECTRON MICROSCOPY IN JAPAN*)

1. ORGANIZATION OF THE CONFERENCE

In a number of countries, National Societies of Electron Microscopy have now been established, bringing together researchers and instrument designers working in the fields of electron microscopy and electronography. To coordinate relations among the National Societies, the International Federation of Societies for Electron Microscopy has been organized, headed by the International Committee on Electron Microscopy.

In accordance with the program for holding conferences on electron microscopy developed by the Committee, national conferences were held in 1955; in 1956, regional conferences; in 1957, national conferences are to be held; and in 1958, an International Congress. The first regional conference of the countries of Europe was held in the second half of September 1956 in Stockholm, and on October 23–27, 1956, in Tokyo, the first regional conference on electron microscopy of the countries of Asia and Oceania was held.

The organizational work for holding this conference was carried out by the Electron Microscopy Society of Japan with the support of the Science Council of Japan and the Ministry of Education.

The composition of the first regional conference of the countries of Asia and Oceania**) and the number of papers read by delegations of various countries are given in Table I.

Table I

The Soviet delegation consisted of V. G. Nyrkov, V. V. Ilyin, A. E. Kriss, V. M. Lukyanovich, G. F. Fedyuk, and G. O. Bakdykhan.

The conference sessions were held over four days according to the following program: the first day—welcoming addresses and survey reports; the second day—electron optics, instruments, and preparation techniques; the third day—biological applications (bacteria, viruses, and histology); the fourth day—industrial applications (physical, metallurgical, and chemical studies).

*) Based on the results of a mission to the first regional conference on electron microscopy of the countries of Asia and Oceania, Tokyo, October 1956.

**) The conference was attended by one representative from the island of Taiwan.

One day was devoted entirely to visits by the conference delegates to three firms manufacturing electron microscopes (the Akachi, Hitachi, and Japan Electron Optics Laboratory firms), as well as to the electron-microscopy laboratory at the University of Tokyo.

For the conference delegates an exhibition of Japanese-made instruments and an exhibition of electron-microscopic photographs illustrating the reported work of Japanese researchers were organized.

The reports delivered at the conference, together with the discussions of the papers, will be published during the current year in the collection Proceedings of the First Regional Conference on Electron Microscopy of the Countries of Asia and Oceania in Tokyo, 1956.

2. BRIEF CHARACTERIZATION OF THE STATE OF ELECTRON MICROSCOPY IN JAPAN

The choice of Japan as the venue for holding the regional conference of the countries of Asia and Oceania was very successful, since the delegates were able to become acquainted with the state of electron microscopy in that country, which occupies first place in the field of electron microscopy among the countries of this geographical region and one of the first places in the world. Japanese-made electron microscopes surpass American ones in resolving power and are approaching the latest developments of the FRG.

In terms of the number of electron microscopes in the country (300 units), Japan occupies third place in the world (after the USSR and the USA). The Japan Society of Electron Microscopy brings together about 700 scientists. At the latest International Conference on Electron Microscopy in 1954 (London), Japan presented about 15% of the total number of papers. At present there are four firms in Japan engaged in the development and production of electron microscopes.

1. Japan Electron Optics Laboratory (Tokyo).
2. Hitachi Central Research Laboratory (Tokyo).
3. Shimadzu Company (Kyoto).
4. Akachi Company (Tokyo).

In addition to the development and production of electron microscopes, the first two firms also conduct serious research with their aid. Besides these four firms, in Japan about four other firms were beginning to engage in the development and production of electron microscopes (for example, the Toshiba firm was developing electrostatic microscopes).

Judging from the reports at the conference and from articles published in journals, scientific-research and experimental-design work in the field of electron microscopy and electron diffraction is being conducted in no fewer than 30 organizations, including 17 universities and institutions of higher learning. Cases of joint work by several organizations, sometimes even located in different cities, are not uncommon.

3. BRIEF CONTENT OF THE REPORTS

On the first day of the conference 9 survey reports were read, devoted to the state of development of electron microscopes in various countries (in the FRG—Prof. Ruska, E.; in Japan—Prof. Tani; in the USSR—Nyrkov, V. G.), as well as to the application of electron microscopy in various fields of science in Japan (investigation of metals and alloys—Prof. S. Koda, viruses—Prof. M. Terada) and in the USA in the fields of cytology and histology (Dr. Mac Clang; Moore, Ruska, Copenhaver, Bennett).

Prof. Ruska gave a historical survey of the development of electron-microscope designs in Germany, beginning in 1932, when he, together with Borries, developed the first model of an electron microscope at the Siemens firm. The speaker dwelt on the description of the electron microscope developed in 1954–1955 by the Siemens firm (FRG), the Elmiskop-1 with a resolution of 9 Å. He also demonstrated the results obtained by Menter on the Elmiskop-1 in a study of phthalocyanine[^1]. In the photograph one can see alternating bands corresponding to crystalline planes filled with metal atoms and located at a mutual distance of 12 Å, which agrees with the distance determined by the X-ray structural method.

In addition to the survey report, Ruska read a paper at the final session on the newest developments of electron microscopes by the Siemens firm.

He reported on a magnetostatic electron microscope with a voltage of 60 kV, developed in 1955, which has the following lenses with permanent magnets: condenser, objective, intermediate, and projection.

This instrument has a resolution of 17–25 Å; in addition, Ruska gave data on an electrostatic microscope (50 kV), developed in 1956, which has a four-electrode gun (of the Steigerwald type) and a lens system consisting of

Fig. 1. Electron-optical system of the HU-10 electron microscope and possible ways of using it: a — electron microscope with high magnification (2 stages of magnification); б — electron microscope with low magnification; в — electron microscope, dark-field image; г — electron microscope with high magnification (three stages of magnification); д — electron-microscopic image from a limited region of the specimen; е — electron diffraction from a limited region of the specimen; ж — electron diffraction with high resolution; з — electron diffraction with high dispersion; и — shadow microdiffraction; к — shadow electron microscope; л — electron diffraction in a convergent beam (Kossel–Möllenstedt diffraction); м — X-ray microscope.

of the objective lens with a stigmator and four projection lenses. In addition to the usual screen, this instrument has a transparent screen behind which a small-format camera is located. The resolution of this instrument is 10–20 Å.

In Ruska’s report, much attention was given to the question of artificial cooling of the object inside the electron microscope. Cooling to minus 100°C reduces the deposition of carbon on the film bombarded by the beam.

Prof. Tani (head of the electron microscopy laboratory of the University of Tokyo), in his survey report devoted to developments in electron microscopes in Japan, reported on the designs of lens systems and accessories for electron microscopes. He described work being carried out in Japan on the study and improvement of electromagnetic lens systems. He devoted much attention to the work of Prof. Kanaya on chromatic aberration. The speaker presented a diagram of the HU-10 electron microscope with two condenser lenses, an objective, an intermediate, and a projection lens, and 12 possible ways of switching on these lenses.

He reported on a 300-kV electron microscope powered by a Van de Graaff generator, developed by the Hitachi firm. On electron micrographs obtained at voltages of 50 and 250 kV, he showed the advantages of the latter.

The speaker described the small table-top electron microscope HM-2 with permanent magnets for standard investigations, developed by the Hitachi firm, as well as a small electron microscope of the Akashi firm, type TRS-50D, having a resolution of 30 Å. The speaker mentioned specimen holders for cooling and heating specimens in the electron microscope. He also described his work on an emission microscope.

The head of the delegation of the Soviet Union, V. G. Nyrkov, in a survey report, described electron microscopes and electron diffraction cameras developed in the USSR.

Prof. Koda (University of Sapporo, Japan) delivered a survey report devoted to the use in Japan of the electron microscope for the study of metals and alloys, in which he reported that of the 300 electron microscopes in Japan approximately one quarter are used for the study of metals and alloys. In the report about 50 photographs were demonstrated and about 40 references were cited to works carried out by Japanese investigators.

a) The author considered work on the electron-microscopic study of thin layers of slip planes in various metals. These works were carried out in 1951 at the universities of the cities of Kyoto and Sendai, as well as in an electrotechnical laboratory, and showed that the distance between slip planes is equal to one or two interatomic distances.

b) Next, the report considered the question of the precipitation of phases from supersaturated solid solutions subjected to aging. These works have been carried out since 1950 at the universities of the cities of Kyoto, Sapporo, and Sendai.

c) Transformations in martensite were studied with the aid of the electron microscope at the universities of the cities of Osaka and Sendai. In this connection fine bands were observed, which may be regarded as slip lines formed during transformation.

d) At the University of Tokyo magnetic alloys with anomalous residual magnetism were studied. It was established that the noticeable residual magnetism is associated with the formation of small ordered regions of ellipsoidal shape within the main disordered phase.

e) The growth of needle-shaped crystals was observed on such metals as zinc, brass, copper, iron, and Wolfram, after heating them in air (Mechanical Laboratory, University of Kyoto) and upon cooling below minus 100°C.

An attachment for cooling to such a temperature was developed at the Institute of Technology and in the Japanese Electron-Optical Laboratory.

f) The structure of metals obtained by evaporation in vacuum was studied. In polycrystalline-like films, twinning of crystals was found (University of Sendai). The transformations in a thin Al—Cu film (50/50) were also observed.

g) The study of fracture surfaces was carried out at the University of Kanazawa. The fracture surface is divided into domains whose dimensions are comparable with the dimensions of crystalline grains.

h) At the Hitachi Central Laboratory the structure of graphite grains in cast iron was studied, and inclusions in steel were also studied; for this purpose a method was developed for obtaining replicas by means of a carbon film obtained by evaporation (University of Tokyo).

On the second day of the conference, 14 reports were delivered.

Prof. Sakaki reported on the work of Lenz (Aachen, FRG), “Some remarks on the calculation of lens fields.” This work critically reviewed two recently published papers on the calculation of the field distribution in electrostatic electron lenses. Simpler and more accurate expressions were proposed for the field distribution in symmetrical three-electrode and asymmetrical two-electrode immersion lenses.

Dr. Morito reported on Lenz’s work “Geometry of the shadow projection of a caustic section.”

To obtain a section of the caustic surface by a plane, Borris proposed using the irreversible changes that occur in a collodion film placed near the rear focal plane of an electron lens in an intense electron beam. Lenz used the caustic section thus obtained to obtain data on the coefficient of spherical aberration and astigmatism on the axis of the electron lens.

Kimura (Hitachi Central Research Laboratory, Japan) spoke about an electron microscope with permanent magnets. This instrument makes it possible to vary the magnification continuously over wide limits (from 2000 to \(20\,000\times\)). The resolving power is better than \(30\) Å.

The author changes the field of the permanent-magnet magnetic lens by changing the magnetic resistance by means of changing the relative position of rods that shunt the magnetic field. The lens system of this microscope consists of two single-gap lenses (objective and projection) and one two-gap lens (intermediate). All lenses use cylindrical magnets made of magnetic steel with the following characteristics: magnetic induction \(1200\) gauss, coercive force \(-650\) oersteds.

In Dr. Kanaya’s report (Electrotechnical Laboratory, Tokyo), “Formation of the Image of Crystalline Objects in the Electron Microscope,” the conditions for the formation of the electron image of crystalline specimens were considered theoretically, from the standpoint of wave optics, taking into account the interaction of electrons with matter. The diffraction image contrast of cubic magnesium oxide crystals was calculated analytically and compared with experimental results.

Prof. Tani reported on Löküan’s work “Interchromatic Contrast—a New Method of Electron Microscopy”1.

Watanabe reported on investigations carried out by him jointly with Nagakawa and Kato (Hitachi Central Research Laboratory and the Kobayashi Institute of Physical Research, Tokyo) on an electron microscope with an accelerating voltage of \(300\) kV, manufactured by Hitachi.

The source of high voltage is a Van de Graaff generator. With the aid of this instrument, electron diffraction patterns were obtained from gold foil \(350\) Å thick at accelerating voltages of \(40\), \(120\), and \(265\) kV. In this work the result obtained by Ellis in 1952 in a narrower voltage interval was reproduced: the contrast of diffraction rings increases in proportion to the square root of the accelerating voltage. To explain this result, it should be assumed that the coefficient of absorption of electrons in matter depends linearly on \(\lg \frac{1}{E}\), where \(E\) is the accelerating voltage. As advantages of such a high voltage, the speaker points to the possibility of using thicker objects for electron diffraction studies. In particular, at an accelerating voltage of \(300\) kV the thickness of aluminum foil may be \(3000\)–\(5000\) Å.

Prof. Sugata (University of Osaka) reported on an electron gun with a filter, developed by him, for monochromatizing an electron beam in an electron microscope operating with ultrahigh electron velocities, for example from a linear accelerator. The fluctuations of electron velocities are less than \(10^{-4}\) at a high current density of the electron beam.

In the work carried out by Apshima, K. Ito, T. Ito, Itsusumoto, Okazaki, and Seki (Japanese Electron-Optical Laboratory, Tokyo), two attachments to the electron microscope were developed, extending the possibilities of its application:

a) A magnetic deflecting device for using the electron microscope both for transmission and for reflection. It consists of two pairs of deflecting coils arranged in the column of the microscope, one of which deflects the electron beam from the optical axis of the instrument, and the second throws it at a certain angle onto the specimen being investigated by the reflection method. Such a device makes it possible to obtain an angle between the electron beam and the plane of the specimen from \(0\) to \(30^\circ\).

b) A device for investigating specimens in a gaseous medium inside the microscope. With the aid of this device the specimen can be observed continuously at gas pressures up to \(10^{-1}\) mm Hg.

Prof. Sakaki reported on work carried out by him jointly with Maruse, Morito, and Komoda (University of Nagoya and the Hitachi Central Research Laboratory). In his report two questions were considered:

a) an attachment to the electron microscope that makes it possible to obtain X-ray microscopic photographs with its aid;

b) a point thermocathode. The speaker described a method for obtaining such a cathode by etching tungsten wire. The method had previously been described by him

together with Mullenshtedt[^3]. Such a thermocathode is a very small and very intense source of electrons.

In the work of Dr. Finch, Dr. Agarwal, Dr. Cherpuri, and Dr. Singh (National Chemical Laboratory, India) a method was reported for improving the vacuum in instruments by surrounding the vacuum leads and other parts of the instrument, which may be the site of a vacuum leak, with a volume in which a preliminary vacuum of approximately \(10^{-1}\) mm Hg is created.

The work of Utiyama and Fukami (University of Tokyo) was devoted to improving the method of preparing replicas using films of evaporated carbon, with extraction of particles included on the surface of the specimen, as well as to the application of this method. The films obtained by evaporation of carbon are chemically inert, mechanically strong, and resistant to electron bombardment.

In the work of Tajima and Ōe (Fuji Photo Film Co., Kanagawa), attention was drawn to the fact that, when determining the resolving power of an electron microscope from the distance between two points or from the blurring of the edge of an image on a photographic plate, it is necessary to minimize the effects caused by the properties of the photographic materials, which depend on the development conditions and, to some extent, on the length of the excitation wave. The communication gives the composition of the developer and the development procedure for two types of photographic emulsions of the firm.

Upshid reported on the work of Dr. Anderson (University of Pennsylvania and the Pasteur Institute, Paris). In this work the possibility was shown of obtaining, on a multilayer “Ektachrome” film, differently colored electron-microscopic photographs, depending on the speed of the electrons, which varied from 40 to 100 keV. With increasing voltage the color of the photograph changed from blue to olive-green, in connection with the increase in the depth of penetration of the faster electrons.

The third day of the conference was devoted entirely to biological applications of electron microscopy. On this day four reports were devoted to bacteriological studies, seven to the study of viruses (of them three reports were read by Prof. A. E. Kriss of the Soviet delegation), and eight reports to histological studies.

The fourth day of the conference was devoted to industrial applications of electron microscopy.

In the report of Arakawa and Prof. Sciuto (University of Kyoto) it was reported that the dispersed state of fillers in vulcanized rubber was studied by means of the electron microscope. Preparations were obtained by the replica method or in the form of very thin sections. The work investigated the relationship between the degree of dispersion of the fillers and the physical properties of the rubber.

Prof. Shun and Dr. Grazenik (Indonesian Institute for Research and Development of Rubber, Indonesia, and Graz, Austria), using the replica method, showed that in hard rubber at room temperature the smallest colloidal particles have a spherical shape and a diameter of about 150–200 Å. Apparently these are molecules with an average molecular weight of 1,500,000. These spherical molecules first form larger particles of approximately 13 molecules and then, by their association, still larger colloidal particles.

Prof. E. Sciuto, K. Takiyama, and N. Ueda (University of Kyoto) studied microcrystals of various colloids by means of the electron microscope. In their report they communicated on the change of two types of microcrystals under electron irradiation, observed by them by the method of microdiffraction. It was shown that needle-shaped crystals of the \(V_2O_5\) sol, grown along the \(b\)-axis by aging to fibrous crystals, change upon heating further into single crystals. Layers of lead, oriented on micromonocrystals of \(PbJ_2\), partially decompose under bombardment by electrons.

R. Ueda and Prof. N. Sasaki reported on their work in which, with the aid of an adapter for processing specimens in a three-lens electron microscope[^4], which made it possible to observe freshly prepared specimens without the need to take them out into the air, they carried out electron-microscopic and microdiffraction studies of changes in metal oxides and metallic oxide catalysts subjected to physical and chemical treatment.

T. Iwai and Dr. K. Watanabe reported on an electron-microscopic study of the products of hydration of Portland cement.

Prof. H. Hashimoto and Prof. K. Tanaka (University of Kyoto) reported on their work, in which they studied the diverse forms of crystals of copper sulfide (\(CuS\), \(Cu_2S\), \(Cu_{1,8}S\)), grown on copper when it was heated in sulfur vapor at different temperatures and pressures. The authors established the mechanism of growth of these crystals.

R. Takagi (Mechanical Laboratory, Tokyo) reported on the study, by means of the electron microscope and electron diffraction, of the process of growth of threadlike crystals on the surface of metals during oxidation.

The author studied the dependence of the form of threadlike crystals on the oxidation temperature. It was found that a needle, once irradiated by electrons, ceases—

gives its growth. The high vapor pressure of zinc allows zinc atoms to evaporate through the ZnO layer and condense not far from the site of evaporation, forming whiskers.

Prof. T. Hibi, K. Hishikawa, and K. Yada (University of Sendai), applying the replica technique, studied single-crystal crystals colored by x-ray radiation, as well as bleached by exposure in air and by heat treatment. Upon coloring, growth of crystals on the surfaces is observed, and upon bleaching—their disappearance.

In an article by Dr. A. R. Deo and Dr. M. K. Ghagpurey (National Chemical Laboratory, India), reported by Dr. H. Kamogawa, it is shown that cadmium and zinc, deposited from the vapor phase, most often form separate crystals. The texture of these layers on such substrates as Formvar, silica gel, and Formvar with a thin silver coating depends on the nature of the substrate and may change owing to the presence of contamination on its surface.

A. Fukami and I. Shiota (University of Tokyo and Krasilnaya Co., Kansai) studied the dispersion of pigments in ultrathin films and sections and the surface of enamel films made from nitrocellulose lacquers.

The aging of dye films prepared by various methods under the action of the atmosphere (natural and accelerated) was investigated.

In the work of Dr. V. S. T. Loubenla, Dr. J. Franet, and Dr. A. L. G. Rice (Prof. H. Hashimoto’s report), the position and orientation of interference fringes observed in electron-microscopic photographs of superposed layered crystals are compared with the corresponding diffraction patterns.

Prof. N. Takahashi, K. Ashinuma, and M. Watanabe (Yamanashi University and the Japan Electron-Optical Laboratory) reported on a new method and apparatus they had developed for preparing thin films of metals and alloys for electron-microscopic and electron-diffraction studies. A small loop of iron wire, protected by alumina or graphite, is lowered into a metal or alloy placed in a graphite crucible in vacuum or in an inert gas, and is slowly drawn out of it. In this way regions several hundred angstroms thick are obtained. Comparative results are described for the study of alloy films obtained by this method and by evaporation in vacuum.

V. M. Lukyanovich (Academy of Sciences of the USSR) reported on the application of electron-microscopic studies to the investigation of the structure of porous bodies.

4. PRINCIPAL WORKS PUBLISHED IN THE JOURNAL “ELECTRON MICROSCOPY”

The Japanese Society of Electron Microscopy publishes two journals, Electron Microscopy (in English and Japanese), which do not duplicate one another and in which articles on electron microscopy, electron diffraction, and related questions are published. In addition, some articles on these topics are published in physical and specialized journals and publications of separate organizations, as well as in foreign journals.

We shall group the articles by individual subjects.

Theoretical works. Among the fundamental theoretical works that have played a major role in the development of electron microscopy in Japan are the works of Dr. K. Kanaya (acting regional secretary of the conference organizing committee). He published the monograph Electron-Optical Theory of the Design of Magnetic Lenses for Electron Microscopes^5, in which material from more than 25 articles written by him in 1949–1955 is combined. In this work the image errors in the electron microscope are consistently considered, and data are given for the practical design of electron microscopes with high resolution. In articles^6, ^7 devoted to improving the resolution in the electron microscope with the aid of electromagnetic lenses having a bell-shaped field form with different degrees of asymmetry, he showed that spherical and chromatic aberrations have a minimum value when the condition \(R_1 : R_2 = 1 : 4\) and \(R_1 : R_2 = 1 : 1.5\) is satisfied, where \(R_1\) and \(R_2\) are the half-widths of the magnetic-field intensity before and after the lens, respectively. He theoretically examined image errors in magnetic lenses of the electron microscope: spherical and chromatic aberration^8, distortion^9, field curvature and astigmatism^10, coma^11. In 1952 he developed the theoretical foundations for the design of a three-stage electron microscope; the question of the errors of electromagnetic lenses of such an electron microscope was considered: spherical and chromatic aberrations^12, distortion^13, field curvature and astigmatism^14. Later Dr. Kanaya published a series of articles devoted to further improvement of the resolution of the electron microscope with a system of complex condenser lenses^15, ^16, ^17. In 1951–1953 he published articles on image errors caused by inaccuracy in the manufacture of pole tips-

… and on the requirements for the manufacturing accuracy of electromagnetic lenses of the electron microscope^19,20. He wrote a series of articles on image formation in the electron microscope from the standpoint of wave optics^21, taking into account the influence of aberrations and defocusing on elastically and inelastically scattered electrons^22,23. Several of Dr. Kanaya’s recent articles are devoted to the study of temperature distribution in the specimens under investigation^24,25. In these articles it is shown that irradiation of an object by an electron microbeam has less effect on raising the temperature of the specimen than does a beam of ordinary cross section. The temperature at the center of the illuminated region is inversely proportional to the square root of the diameter of the irradiated area. In this connection he recommends, for electron microscopes with high resolution, the use of a double condenser lens, which makes it possible to obtain on the object an electron beam of very small diameter.

An article on the theory of image formation in the electron microscope has also been published by R. Uyeda^26.

Research and development of elements of electron optics. Articles devoted to the research and development of elements of electron optics are of great interest, since in Japan, from our point of view, the greater part of the research work in this field is predominantly practical in character, aimed at solving practical problems of improving the quality of electron optics and carried through to practical application. From this standpoint the articles of S. Katagiri (Central Research Laboratory, Hitachi)^27,28,29 are of interest; they are devoted to the study and reduction of chromatic aberration in the magnetic microscope. In these articles it is shown that the chromatic aberration for points removed from the axis can be compensated by a suitable combination of two lenses and by an appropriate design of the pole pieces. The chromatic aberration for points removed from the axis consists of the chromatic aberration of magnification and of rotation. The coefficient of chromatic aberration in this case is \((C_{Fmr})^2 = (C_{Fm})^2 + (C_{Fr})^2\), where \(C_{Fm}\) and \(C_{Fr}\) are, respectively, the coefficients of the chromatic aberrations of magnification and rotation. For certain values of the pole-piece parameter

\[ \frac{h}{d} \]

(\(h\) is the slot width, \(d\) the internal diameter of the pole pieces), one can find such a value of the lens parameter

\[ \frac{IN}{\sqrt{E}} \]

at which \(C_{Fm}\) becomes equal to zero. In this case the coefficient of chromatic aberration for points removed from the axis is determined only by the coefficient of rotation aberration, which may have a positive or negative value depending on the direction of current through the electromagnetic lens. With a corresponding choice of the direction of current through the system of lenses, a minimum value of the total chromatic aberration of this system can be obtained by compensation.

In the case of a simple system of two lenses, satisfactory compensation can be obtained only in a narrow range of magnifications. The author proposes to expand the possibilities of the method by means of complex systems of lenses. The articles of this author also describe a method for controlling the centering of the lenses of an electron microscope by measuring chromatic aberration with the aid of an alternating component artificially superposed on the constant accelerating voltage. In an electron microscope compensated in this way, an image with chromatic aberration can yield a resolution of about 50 Å even with fluctuations of the accelerating voltage up to 1%. The value of this method also lies in the fact that it permits compensation of chromatic aberration which arises, even in the presence of extremely monochromatic primary radiation, as a result of the loss of velocity by electrons during scattering in the specimen.

An article by N. Morito^30 is devoted to the calculation of the chromatic aberration of an electromagnetic lens of an electron microscope.

In another article, written jointly with K. Koizumi^31, the astigmatism of an electromagnetic lens was studied theoretically and experimentally. It is shown that astigmatism can be compensated in the first approximation by adding an auxiliary elliptical lens.

The staff of the electron-optical laboratory K. Ito and T. Ito devoted a series of articles to the investigation of electromagnetic lenses of the electron microscope. In one of the articles^32 they calculated the distortion coefficient and compared the results of the calculation with those obtained from photographs of a diffraction grating.

The same authors, together with E. Sugata and Nishitani^33, published an article on measuring the distribution of the field in magnetic electron lenses by measuring the rotation of the image. The essence of this original method consists—

*) \(IN\) is the number of ampere-turns of the lens; \(E\) is the accelerating voltage.

in that they measure the difference in rotation angles \(\Delta \theta\) of the image of two very thin wires arranged along the axis at a certain distance \(\Delta z\) from one another. In this case the field strength on the axis can be calculated by the formula

\[ H_{(z_0)}=\frac{\sqrt{V}}{0.15}\cdot \frac{\Delta \theta}{\Delta z}. \]

In the following article K. Ito and T. Ito \(^{34}\) consider the problem of correcting lens defects in a three-lens electron microscope by means of a compound objective and projection lens.

Sugata, Nishitani, and Hamada \(^{35}\) applied a method for measuring the field distribution of a lens from the rotation of the image to an electromagnetic lens with saturation. Using the measured field distribution, they calculated certain constants: the focal length, the position of the principal planes, and the constants of spherical and chromatic aberration.

In another paper, Sugata, Nishitani, and Hirose \(^{36}\), applying the same method of measuring the field distribution in an electromagnetic lens, found that for a certain shape of pole pieces there is a leakage of the magnetic field, which can be eliminated by changing the shape of the pole pieces.

At the same time, the maximum of the magnetic field increases. The authors point out that in lenses with a large number of ampere-turns measures should be taken so that the saturation of the pole pieces is not too great.

A method for measuring the spherical aberration and astigmatism of an electron lens from shadow electron-microscopic images of crossed diffraction gratings was proposed in two articles by Sakaki, Maruse and Maruse, and Eguchi \(^{37,38}\).

Hibi and Takahashi \(^{39}\) clarified the influence of the material from which the diaphragm placed in front of the objective lens is made on the resolving power of the electron microscope. The best resolution was obtained with a silver diaphragm, and with prolonged operation of the instrument, with a gold diaphragm.

Among the articles published in the journal Electron Microscopy, only two articles \(^{40,41}\) are devoted to the study of illumination systems. The author of one of them determined the quantities necessary for the design of an electron gun—the required current density in the electron beam when photographing by direct irradiation of a photographic plate with electrons, when photographing with a luminescent screen, and when visually observing on a screen. The authors of the second article checked the relation between the angular aperture of the illumination system, the illuminated area of the specimen, and the intensity of the electron beam.

Development of instruments and accessories. In the article by Tanaka and Hashimoto \(^{42}\), the design of a universal electron microscope with a condenser, objective, and two projection lenses is described, which possesses various possibilities of application. It can be used for the following seven methods of investigation:

a) an electron microscope with continuous magnification from 800 to \(20\,000\times\); b) electron microdiffraction, c) dark-field electron microscope, d) high-resolution electronograph, e) electronograph with a large effective length (up to 250 cm), f) shadow electron microscope, g) shadow (probe) microdiffraction.

The specimens under study can be heated, and up to two kinds of substances can be evaporated onto them inside the instrument. The evaporator can also be used to neutralize charges on specimens.

An electron microscope that can be used both for electron-microscopic and for electron-diffraction investigations by the transmission method and by the reflection method is described in the article by K. Ito, T. Ito, and M. Watanabe \(^{43}\).

In another article by the same authors et al. \(^{44}\) an electron microscope with a high-temperature furnace (up to \(1000^\circ\) C) is described. The use of the instrument has been demonstrated in studies of transformations in the Al—Cu alloy by the electron-transmission method and of phase precipitation from the Al—Mg—Si alloy by the reflection method.

An experimental 300-kV electron microscope with a Van de Graaff generator, developed by the Hitachi firm and Nagoya University, is described in article \(^{45}\).

H. Watanabe \(^{46}\) described an electron-velocity analyzer with which voltage pulsations superimposed on the accelerating voltage were detected when the filament is supplied with alternating current. The pulsations are practically eliminated when a filament with a center tap is introduced.

Sasaki and Ueda \(^{47}\) described the design of an attachment to an electron microscope, with the aid of which the authors observed freshly prepared specimens without exposing them to air. This attachment makes it possible to observe one and the same region

of the specimen before and after physical and chemical treatment. The process of reduction and oxidation was observed on \(WO_3\), \(MoO_3\), and \(Fe_3O_4\).

In the article by Hibi T.\(^{48}\) it is reported that the use, as a thermocathode, of a tungsten tip obtained by mechanical polishing (tip radius \(1\,\mu\)) or by electrolytic etching in a NaOH solution (tip radius \(0.1\,\mu\)) made it possible to obtain a very intense source of electrons of extremely small size. This is demonstrated by photographs of magnesium-oxide crystals, on the edges of the images of which up to 20 Fresnel fringes are observed. The author asserts that such a thermocathode may make it possible to obtain higher resolution with a two-lens electron microscope without using a double condenser lens, a stigmator, and an intermediate lens.

In the article by Araki\(^{49}\) an electron microscope with a single stage of electron magnification is described; its resolving power occupies an intermediate position between that of a light microscope and that of an electron microscope. In this instrument, in contrast to ordinary electron microscopes, the electron projection lens is replaced by a light-optical magnifying system. The photographs obtained have a large field of view; electronograms and electron-microscopic photographs are obtained without moving the specimen. However, the electron-microscopic photographs presented by the author have low resolution. An analogous work was published by a group of other authors\(^{50}\). They introduced an intermediate photomera into an ordinary electron microscope. With the aid of this instrument, simultaneously with an ordinary, strongly magnified image of a very small part of the specimen, an intermediate image formed by the objective (with a resolution of about 500 Å) with medium magnification and a large field of view can be obtained. Apparently, these works in Japan did not receive further development.

The construction of sources of supply for electron microscopes is devoted, in the journal “Electron Microscopy,” to only two articles (voltage and current stabilizers), published in 1950–1951\(^{51,52}\).

Preparation technique. The development of the replica method in Japan is being carried out mainly by the electron-microscopy laboratory of the University of Tokyo, headed by Prof. Tani.

A series of articles on the technique of preparing replicas was written by A. Fukami and other collaborators of this laboratory\(^{53,54,55,56,57}\). In these articles the reliability of known methods of preparing replicas is examined, and improved methods are proposed for preparing replicas from certain organic materials (gelatin, methyl methacrylate, collodion, and cellophane films). To strengthen the replicas, collodion and collodion are applied to the reverse side. The resolution in photographs obtained from replicas was determined by these authors from the roundedness of sharp angles in the image of the specimen. Two articles by Tsushikura\(^{58,59}\) are devoted to the same question. They describe a method of preparing two-stage replicas in which the first stage is obtained by polymerization of methyl methacrylate or from molten ethyl-methacrylate polymer, and the second by condensation of a thin metallic layer of aluminum, chromium, or germanium. The resolution was determined from the radius of curvature at the corners of particles. Kaolin was used as the standard specimen.

Hibi and Yada\(^{60}\) dealt with the improvement of metallic films obtained by evaporation in vacuum for the two-stage replica method. It was found that such elements as Zr, Si, and Fe are more suitable than Al for obtaining high-resolution replicas. Further improvement of replicas with high resolution was obtained by preliminary ion or electron bombardment of a plastic film.

The technique for obtaining thin carbon films by evaporation in vacuum, the properties of these films, and their application in the replica method with extraction of particles from the surface of the specimen are described in two articles by Fukami and Iotsumoto\(^{61,62}\).

In the article by Hibi\(^{63}\) a device with a magnetron is described for shadowing preparations with metals; its use gives better results with the materials used earlier and also makes it possible to use, for shadowing, metals that could not be used in the ordinary method.

Applications of electron microscopy. Articles devoted directly to investigations with the aid of an electron microscope contain chiefly the results of the study of metallic materials*).

Koda and Takeyama\(^{64}\) investigated the precipitation of phases from a supersaturated solid solution Al—Ag. Ueda R.\(^{65}\), using an emission electron microscope constructed by him, investigated the microstructure of austenitic steel at high temperatures. He traced the continuous growth of austenite grains.

*) Applications of electron microscopy in the field of biology are not considered in the present review.

In the work of Taoka and Sakata\(^{66}\), when studying the structure of the surface of recrystallized grains in the Ni—Fe alloy, various types of structures were observed, which depend on the crystallographic orientation of the surface. The authors assume that the thin steps observed on the grain surface are monoatomic layers.

Tani, Ikeya, and Ono\(^{67}\) used an electron microscope to study the structure on the fracture surface of metallic materials (Fe and Al alloys) during fatigue testing.

The influence of the rate of deformation propagation at room temperature on the appearance of slip bands in an aluminum single crystal is described in article\(^{68}\). When the deformation rate was decreased, broader slip bands were observed, the distance between them increased, and the number of bands decreased.

With the aid of an electron microscope, details in graphite grains on the surface of cast iron subjected to cathode bombardment in vacuum were investigated\(^{69}\). The article presents experimental results concerning the crystalline structure and the process of formation of graphite spherulites.

In the work of Miura and Tamamushi\(^{70}\), the relationship was investigated between the spectral transmission of gold sol, prepared by various methods, and the size and shape of its particles, determined with the aid of an electron microscope.

Etsuji, Tani, and Ikeya\(^{71}\) studied, with the aid of an electron microscope and by the method of two-stage replicas, the surface structure of photosensitive selenium. Stereoscopic images revealed that each Se grain consists of small spherical mosaic crystals, changing their size with the temperature and pressure at which the layers were prepared. The article also shows that on the surface of selenium photoelements coated with a cadmium layer by cathode sputtering, the particles of the latter are distributed uniformly, whereas during evaporation onto a collodion film hexagonal Cd crystals are formed.

The structure of crystals of metal oxides obtained during combustion of the latter (condensed smoke) was studied with the aid of an electron microscope by a number of authors.

In article\(^{72}\) a specimen holder is described, constructed in such a way that the specimen can rotate about an axis perpendicular to the optical axis of the instrument, and MoO\(_3\) crystals could be observed at different angles.

Hibi and Yada\(^{73}\) studied, by the replica method, the smoke of magnesium and molybdenum oxides. Various modes of bonding of cubic magnesium oxide crystals were found. In the images a remarkable growth of crystals was observed.

Article\(^{74}\) is devoted to the study, with the aid of an electron microscope, of the process of dehydration and decomposition of the hydration products of Portland cement.

In work\(^{75}\), with the aid of an electron microscope and cinematographic recording of electron diffraction patterns, the dependence on temperature of the rate of the \(\alpha \to \beta\) transformation of phthalocyanine copper was studied, as well as the form of this transformation.

In two articles\(^{76,77}\) changes are considered which occur in a specimen under intense and prolonged irradiation by an electron beam. During electron bombardment, a thin film is formed on the surface of the preparations, which can be separated when the specimen is dissolved. Its formation is explained by polymerization of certain substances present on the surfaces, and by ionization of the materials under the action of the electron beam.

5. BRIEF CHARACTERISTICS OF CERTAIN FIRMS AND ORGANIZATIONS ENGAGED IN ELECTRON MICROSCOPY

In accordance with the conference program, for the foreign delegates a visit was organized to three firms producing electron microscopes, located in Tokyo and its suburbs, and to the University of Tokyo.

a) Japan Electron Optics Laboratory (president Dr. K. Kazato). This firm, along with the Hitachi firm, is a leading one in the field of development and manufacture of electron microscopes in Japan. It was organized after the war in 1945. Its principal personnel consisted of physicists, electrical engineers, mechanical engineers, specialists in optics, radiolocation, and aviation instruments from the former Technical Research Department of the Ministry of the Navy of Japan. In the postwar years this laboratory has produced more than 10 types of electron microscopes.

The firm has developed: 1) an easy-to-operate electron microscope with low magnification; 2) a transmission electron microscope with high resolution; 3) an electron microscope with a three-stage lens system; 4) an electron microscope for investigation by the methods of transmission and reflection; together with this, the instrument makes it possible to obtain microscopic images or electron diffraction patterns of specimens without changing their position; 5) an electron

a microscope with devices for heating and deep cooling of specimens; 6) an electron microscope with accelerating voltage up to 200 kV; 7) an electron microscope for studying secondary emission from a surface; 8) an electron microscope with a sector for electron diffraction.

The laboratory is conducting research work on the calculation of electron trajectories, the study of the interaction of electrons with matter, the application of electron microscopes, the improvement of power-supply devices for them, the design improvement of electron microscopes, and the development and experimental production of new electron microscopes.

The first electron microscope with electrostatic optics was created by the firm in 1946.

In 1949 an electron microscope with electromagnetic optics and a resolution of 50 Å was created (type JEM-1).

In 1950 the JEM-2 type was developed with the same resolution. Its optics contained three lenses: objective, intermediate, and projection. In the same year the JEM-3 was developed with a resolution of 30 Å, and in 1951—the JEM-4 with a resolution of 20 Å. In 1952 a double condenser was introduced into the illuminating system; the objective had a stigmator.

Fig. 2. Alignment room for electron microscopes of the Japanese electron-optical laboratory. On the right is the JEM-T1 electron microscope; on the left are three JEM-T4 electron microscopes.

In 1953 the JEM-5 type was developed with a resolution of 15 Å. Its optical system contains a double condenser, a double objective with a stigmator, and intermediate and projection lenses. The accelerating voltage in this instrument is 50–100 kV.

In addition to new types of instruments with fundamentally modified electron optics and power-supply circuits, the firm produces modernized types of instruments in which only individual assemblies have been changed (for example, JEM-5A, JEM-5B, JEM-5C, JEM-5G, JEM-5H, etc.).

At present the firm manufactures the following electron microscopes: JEM-T1 (the simplest and most suitable for industrial research); JEM-T4 and the JEM-5 type with various indices. The varieties of JEM-5-type instruments differ mainly in the design of the specimen chamber and, accordingly, in their different fields of application.

Thus, for example, the JEM-5G instrument permits electron-microscopic and electron-diffraction investigations by the transmission and reflection methods. During the investigation, specimens may be heated inside this instrument to 1000°C, cooled to minus 160°C, and subjected during observation to the action of gas at pressures up to 0.1 mm Hg.

The firm accepts orders not only for serially manufactured models, but also for the development of new electron microscopes according to customers’ technical specifications. The results of research work are rapidly transferred to production, and new or improved technical characteristics of an instrument are introduced within three months after the completion of the research stage. As stated by the president of the elec-

in the electron-optical laboratory, Dr. Kazato, in conversation with the Soviet delegation, [said that] in the development of instruments the main attention is paid to high operational qualities (they are not sacrificed to the simplicity of the instrument). On some instruments the laboratory has succeeded in obtaining a resolution of 8 Å. The firm has produced about 100 electron microscopes. It exports them to France, where it has its own representative office, and to Belgium.

b) The Central Research Laboratory of Hitachi (director Dr. T. Kikunuta). In a brief presentation, the head of the laboratory described the Hitachi firm. It was organized for the production of mining electrical equipment. The profile of this firm is very broad. At present it is engaged in machine building (heavy, transport, agricultural, etc.) and at the same time in the production of precision scientific instruments (including electron microscopes).

Fig. 3. Electron microscope of the Japanese Electron-Optical Laboratory, type JEM-5G.

Fig. 4. Electron microscope of the Hitachi firm, type HU-10.

The main research connected with this production is carried out in the Central Research Laboratory, which has a staff of about 300 people (physicists, chemists, electrical engineers, metallurgists, and mechanics).

We were shown the HU-10 electron microscope with a resolution of 10–15 Å and one of the latest developments—an instrument for analyzing electrons by velocity. In addition, an electron microscope with an accelerating voltage of 300 kV, powered by a Van de Graaff generator, was shown. The instrument is installed in an air-conditioned room.

No definite advantages of ultrahigh voltage for electron-microscopic investigations are yet felt. For the time being, apparently, there is only one advantage of such a voltage—the possibility of obtaining electron diffraction patterns from comparatively thick specimens.

According to incomplete advertising data, the Hitachi firm developed the following types of electron microscopes, now discontinued:

HU-6 with a resolution of 30 Å, accelerating voltage 50 kV (1950);

HS-2 50–100 Å, 50 kV (1952);

HU-8 (console type) 30 Å, 50 kV (1952);

HU-9 (1955).

At present the firm produces three types of electron microscopes: a universal microscope with high resolution HU-10; a microscope with medium

Fig. 5. Electron microscope of the Hitachi company, type HS-5.

Fig. 6. Electron microscope of the Hitachi company, type HM-2.

Fig. 7. Electron microscope of the Akashi company, type TRS-50D.

Fig. 8. Electron microscope of the Shimadzu company, type SMV-80.

with a resolution of HS-5, with permanent-magnet lenses, and a compact desktop microscope HM-2 with a resolution of 100 Å and permanent-magnet lenses.

Akachi Company. The Akachi company was organized about 40 years ago. It specialized in the production of instruments for the mechanical testing of materials. It has been engaged in the production of electron microscopes for about 5 years. It apparently does not carry out independent development and research work in electron optics. The Akachi company produces only one type of electron microscope, TRS-50D, with a resolution of 30 Å.

Shimadzu Company. This company has existed since 1875. It produces physical and chemical laboratory instruments, precision measuring instruments, X-ray and vacuum instruments, as well as electron microscopes of two types: SMV-80 (vertical model) and SM-C3 (horizontal model). As a result of our acquaintance with the electron microscopes of this company at the exhibition (because the enterprises of this company are located in the city of Kyoto, our delegation did not visit them), the impression is created that they are inferior to the instruments of the Japanese Electron Optics Laboratory and the Central Research Laboratory of Hitachi.

Fig. 9. Electron microscope of the Shimadzu company, type SM-C3.

According to incomplete advertising data, the Shimadzu company developed the following types of electron microscopes, which by the present time have been discontinued:

1950: SM-1 (console type), voltage 60 kV;
1950: SM-2, voltage 40 kV, resolution 50 Å;
1951: SM-C2 (horizontal), voltage 50 kV, resolution 50 Å;
1952: SM-U6 (vertical), voltage 50 kV, resolution 30 Å.

Electron Microscopy Laboratory of the University of Tokyo. The University of Tokyo is the largest national institution of higher education. It was organized in 1869 by the merger of three different institutions of higher education, created at the end of the eighteenth century and in the middle of the nineteenth century. At present it has 9 faculties, 5 graduate divisions, and 12 research institutes. It has 10,000 students. At the university we were shown the electron microscopy laboratory, headed by Prof. Tani (chairman of the organizing committee of the conference). This is a small laboratory: it has about 5 permanent staff members. In addition, the laboratory has a varying contingent of employees undergoing training similar to postgraduate study. This laboratory has trained about 20 doctors of science, who are very highly regarded by the scientific institutions of Japan. The laboratory is mainly concerned with two questions: the study of the structure of dyes and the development of the method of carbon replicas with extraction. The laboratory conducts some research work jointly with the indicated higher firms.

The main instrument of the laboratory is the electron microscope JEM-5, developed by this laboratory jointly with the Japanese Electron Optics Laboratory.

6. TECHNICAL CHARACTERISTICS OF ELECTRON MICROSCOPES CURRENTLY PRODUCED IN JAPAN

All electron microscopes produced in Japan may be divided into three groups:

a) universal microscopes with high resolution (10–15 Å);
b) simpler and smaller electron microscopes with medium resolution (about 25 Å);
c) electron microscopes of the simplest design and operation, with comparatively low resolution (50 Å and higher).

A comparative table of Japanese electron microscopes is given below. Most electron microscopes have electromagnetic lenses; two types (HS-5, HM-2) have lenses made of permanent magnets; electrostatic electron microscopes are neither produced nor being developed at all. As a rule, electron microscopes are made with shielded electron guns and high-voltage units assembled in oil-filled tanks, which is essential for instruments operating in the humid climate of Japan, since this prevents charge leakage along the surface and high-voltage corona.

The source of electrons is most often a V-shaped tungsten filament cathode. An exception is the instrument of the Akashi firm, in which a pointed platinum oxidized thermocathode is used. In recent years, some laboratories have been carrying out studies aimed at obtaining thermionic emission from a pointed tungsten cathode. Little importance is attached to questions of the configuration of the electrodes of the electron gun.

Table II

Comparative table of Japanese electron microscopes.

Most instruments make it possible to obtain diffraction from a limited area of the specimen (up to 1 μ²) by the electronogram method of shadowing and reflection. However, the field of the electronograms is then insufficiently large.

In high-resolution instruments a double condenser lens is invariably used, by means of which it is possible to reduce the beam cross section on the specimen to 4 μ.

In instruments with medium resolution, a single condenser lens is used, and in simplified instruments the condenser lens is absent.

In Dr. Kanaya’s opinion, expressed in a private conversation, without a condenser lens a resolution better than 30 Å cannot be obtained.

The specimen chamber in universal instruments has many attachments that expand the application of the instruments. Especially universal is the specimen chamber of the JEM-5G instrument.

In most instruments the specimen is placed outside the pole pieces. The lens system in the majority of instruments, with the exception of a few of the most...

simplified instruments, consists of three lenses: objective, intermediate, and projection. The objective lens of the JEM-5 instrument is double. The objective lens of instruments with high and medium resolution has a stigmator consisting of ferromagnetic rods, the distance of which from the axis of the instrument and their rotation through a certain angle around it can be adjusted during operation of the instrument by means of a handle brought outside.

In simpler instruments (TRS-50D), in order to adjust the stigmator it must be removed from the instrument.

Hitachi HU-10 electron microscopes have a lens system with compensated chromatic aberration at the aperture described in Section 4. According to the data of this firm, this instrument makes it possible to obtain a guaranteed resolution (15 Å) without the use of a stigmator. The latter is used only in the case of contamination of the diaphragms of the pole pieces, causing distortions of the field of the lenses.

In instruments with high and medium resolution, the illumination system and lenses are adjusted by means of setting screws.

All electron microscopes have loupes with small magnification, or small light microscopes, for precise focusing of the image on the screen.

The cameras of universal instruments make it possible to obtain a very large number of photographs on a single loading. For example, the HU-10 instrument makes it possible to obtain up to 36 photographs measuring \(50 \times 50\) mm on photographic plates.

The camera of the JEM-5 instrument makes it possible to remove from the instrument, without disturbing the vacuum, any number of exposed photographic plates.

Some electron microscopes have an auxiliary vacuum chamber for preliminary degassing of photographic plates. To monitor the vacuum in the instruments there is a Pirani gauge or a gas-discharge tube.

A review of the development of electron-microscope instrument making in Japan shows that in 1951 instruments with three lenses (objective, intermediate, and projection), having a resolution of 20 Å, were created (JEM-4A and JEM-4B).

In 1952 an instrument with a double condenser and a stigmator in the objective lens was created, giving a resolution of 20 Å (JEM-4C).

In 1953, in addition, a double objective was used in the instrument. A resolution of 15 Å was achieved (JEM-5A and JEM-5B).

Thus, in 1953 the electron optics of a high-resolution instrument was created, which has been preserved up to the present time—with a double condenser, double objective, having a stigmator, intermediate and projection lenses, and corrected chromatic aberration, giving a resolution of 15 Å. On some of the best specimens of instruments, at the present time a resolution of up to 8 Å has been achieved.

7. EXHIBITION OF JAPANESE-MADE INSTRUMENTS

At the exhibition organized for the delegates of the conference, some types of electron microscopes of the four organizations listed above were demonstrated in operation.

In addition, the Shimadzu firm exhibited a prototype of a shadow X-ray microscope and some photographs obtained with its aid (the instrument itself was not demonstrated in operation). The instrument has the following characteristics: resolution \(1\,\mu\), direct magnification from \(20\times\) to \(100\times\), together with photographic magnification up to \(1000\times\). Accelerating voltage 10 kV.

Also demonstrated at the exhibition were instruments manufactured by Shimadzu and the Japan Electron Optics Laboratory, intended for general vacuum work and for preparing specimens for electron-optical investigations.

Several firms in Japan produce microtomes for sections of thickness from one micron and more, and ultramicrotomes for sections of \(0.02\,\mu\) and more. The cutting tool in all ultramicrotomes is glass. These instruments were demonstrated at the exhibition and during visits to the firms.

Hitachi manufactures the UM-2 ultramicrotome, with stepwise feed of the knife by elastic deformation of the supporting rod. The amount of feed is regulated from 0.3 to \(0.05\,\mu\). The specimen moves in a circle.

The Electron Optics Laboratory produces an ultramicrotome with specimen feed by thermal expansion of the rod on which the specimen is mounted. The section thickness is \(0.02\,\mu\).

Shimadzu manufactures the “K” model microtome. In this instrument, by simple changing of the gears, sections can be obtained in two ranges: from 0.04 to \(0.12\,\mu\) (ultrathin sections) and from 1 to \(3.5\,\mu\) (ordinary thin sections). The knife-feed mechanism is a gear reducer.

According to advertising data, the firm “Japan Microtome” is also engaged in the manufacture of microtomes and ultramicrotomes. It produces microtomes of the following types:

RM — section thickness from 0.5 to 25 μ, RU — section thickness from 0.05 to 5 μ, RU-3 — section thickness from 0.02 to 5 μ.

In conclusion, mention should be made of the great work carried out by the Organizing Committee of the First Regional Conference on Electron Microscopy of the Countries of Asia and Oceania, which ensured the creation of a businesslike atmosphere and the most favorable conditions for the fruitful work of the conference, as well as of the unfailing attention and assistance on the part of the scientists of Japan, shown to the Soviet delegation from the first to the last day of its stay in that country.

G. O. Bagdykyants

CITED LITERATURE

1. J. W. Menther, Proc. Roy. Soc. A, 236, 119 (1956).
2. M. Locquin, C. R. Acad. Sc. (Paris) 242, 1713 (1956).
3. J. Sakaki, Mollenstedt G., Optik 13, 193 (1956).
4. N. Sasaki, R. Ueda, J. El. Micr. 2, No. 2, 25 (1952) (Jap.).

a) Theoretical works

1. K. Kanaya, Res. Electrotechn. Lab. 548, 1, 1955.
2. K. Kanaya, Bull. Electrot. Lab. 13, 338 (1949).
3. K. Kanaya, J. El. Micr. 1, No. 2, 53 (1950) (Jap.).
4. K. Kanaya, Bull. Electrot. Lab. 15, 86 (1951).
5. K. Kanaya, Bull. Electrot. Lab. 15, 91 (1951).
6. K. Kanaya, Bull. Electrot. Lab. 15, 193 (1951).
7. K. Kanaya, Bull. Electrot. Lab. 15, 199 (1951).
8. K. Kanaya, Bull. Electrot. Lab. 16, 25 (1952).
9. K. Kanaya, Bull. Electrot. Lab. 16, 135 (1952).
10. K. Kanaya, Bull. Electrot. Lab. 16, 184 (1952).
11. K. Kanaya, Bull. Electrot. Lab. 17, 529 (1953).
12. K. Kanaya, Bull. Electrot. Lab. 17, 582 (1953).
13. K. Kanaya, Bull. Electrot. Lab. 18, 13 (1954).
14. K. Kanaya, Bull. Electrot. Lab. 15, 203 (1951).
15. K. Kanaya, Journ. Shimadzu Rev. 9, 28, 1952.
16. K. Kanaya, J. El. Micr. 1, No. 1, 7, 1953 (Engl.).
17. K. Kanaya, J. El. Micr. 2, 1 (1954); Bull. Electrot. Lab. 18, 517 (1954).
18. K. Kanaya, Bull. Electrot. Lab. 17, 679 (1953).
19. K. Kanaya, Bull. Electrot. Lab. 17, 756 (1953).
20. K. Kanaya, J. El. Micr. 3, 1 (1955) (Engl.).
21. K. Kanaya, J. El. Micr. 4, 1 (1956) (Engl.).
22. R. Ueda, J. Phys. Soc. Japan. 10, 256 (1955).

b) Research and development of elements of electron optics

1. S. Katagiri, J. El. Micr. 1, No. 1, 13 (1953) (Engl.).
2. S. Katagiri, J. El. Micr. 3, No. 1, 21 (1953) (Jap.).
3. S. Katagiri, Rev. Sci. Instr. 26, 870 (1955).
4. N. Morito, J. El. Micr. 3, No. 2, 1 (1954) (Engl.).
5. N. Morito, K. Koizumi, J. El. Micr. 2, No. 2, 22 (1952) (Jap.).
6. K. Ito, T. Ito, J. El. Micr. 1, No. 2, 45 (1950) (Jap.).
7. E. Sugata, Y. Nishitani, K. Ito, T. Ito, J. El. Micr. 1, No. 1, 1 (1953) (Engl.).
8. K. Ito, T. Ito, J. El. Micr. 3, No. 1, 12 (1953) (Jap.).
9. E. Sugata, Y. Nishitani, H. Hamada, J. El. Micr. 3, 9 (1955) (Engl.).
10. E. Sugata, Y. Nishitani, S. Hirosue, J. El. Micr. 4, 49 (1956) (Engl.).
11. Y. Sakaki, S. Maruse, J. El. Micr. 2, No. 1, 8 (1954) (Engl.).
12. S. Maruse, I. Eguchi, J. El. Micr. 3, No. 1, 17 (1953) (Jap.).
13. T. Hibi, S. Takahashi, J. El. Micr. 2, 27 (1950) (Jap.).
14. E. Sugata, J. El. Micr. 4, No. 3, 54, 1956 (Jap.).
15. H. Eto, S. Okada, J. El. Micr. 1, No. 2, 41 (1950) (Jap.).

c) Development of instruments and accessories

1. K. Tanaka, H. Hashimoto, J. El. Micr. 3, No. 1, 7, 1953 (Jap.).
2. K. Ito, T. Ito, M. Watanabe, J. El. Micr. 2, 10, 1954 (Engl.).
3. N. Takahashi, T. Takeyama, K. Ito, T. Ito, K. Mihama, M. Watanabe, J. El. Micr. 4, 16, 1956 (Engl.).
4. B. Tadano, Y. Sakaki, S. Maruse, N. Morito, J. El. Micr. 4, 5, 1956 (Engl.).

1. H. Watanabe, J. El. Micr. 4, 24, 1956 (in English).
2. N. Sasaki, R. Ueda, J. El. Micr. 2, No. 2, 25, 1952 (in Japanese).
3. T. Hibi, J. El. Micr. 4, 10, 1956 (in English).
4. J. Araki, J. El. Micr. 1, No. 2, 56, 1956 (in Japanese).
5. E. Sugata, M. Tateishi, H. Yokoya, Y. Nishitani, J. El. Micr. 3, No. 1, 3, 1953 (in Japanese).
6. K. Takahashi, D. Karasawa, J. El. Micr. 1, No. 2, 47, 1950 (in Japanese).
7. K. Takahashi, J. El. Micr. 2, No. 1, 33, 1951 (in Japanese).

c) Preparation Methods

1. A. Fukami, K. Adachi, S. Nagakawa, J. El. Micr. 1, No. 2, 49, 1950 (in Japanese).
2. A. Fukami, J. El. Micr. 2, No. 1, 59, 1951 (in Japanese).
3. A. Fukami, T. Akiyama, J. El. Micr. 1, No. 1, 28, 1953 (in English).
4. A. Fukami, J. El. Micr. 2, No. 1, 20, 1954 (in English).
5. A. Fukami, J. El. Micr. 3, No. 2, 16, 1954 (in Japanese).
6. H. Tsushikura, J. El. Micr. 1, No. 2, 37, 1950 (in Japanese).
7. H. Tsushikura, J. El. Micr. 2, No. 1, 15, 1954 (in English).
8. T. Hibi, K. Yada, J. El. Micr. 3, No. 1, 30, 1953 (in Japanese).
9. A. Fukami, J. El. Micr. 4, 31, 1956 (in English).
10. A. Fukami, H. Yotsumoto, J. El. Micr. 4, No. 3, 46, 1956 (in Japanese).
11. T. Hibi, J. El. Micr. 2, No. 2, 59, 1952 (in Japanese).

d) Applications of Electron Microscopy

1. S. Koda, T. Takeyama, J. El. Micr. 1, No. 1, 39, 1953 (in English).
2. R. Ueda, J. El. Micr. 1, No. 1, 42, 1953 (in English).
3. T. Taoka, S. Sakata, J. El. Micr. 4, 41, 1956 (in English).
4. Y. Tani, M. Ykeya, T. Ono, J. El. Micr. 2, No. 1, 49, 1954 (in English).
5. H. Nishimura, J. Takamura, El. Micr. 1, No. 2, 35, 1950 (in Japanese).
6. H. Tsushikura, T. Kusakawa, T. Okumoto, J. El. Micr. 4, No. 1, 26, 1955 (in Japanese).
7. K. Miura, B. Tamamushi, J. El. Micr. 1, No. 1, 36, 1953 (in English).
8. M. Eguchi, Y. Tani, M. Ykeya, J. El. Micr. 1, No. 2, 58, 1950 (in Japanese).
9. S. Shimadzu, J. El. Micr. 2, No. 1, 54, 1954 (in English).
10. T. Hibi, K. Yada, J. El. Micr. 2, No. 1, 45, 1954 (in English).
11. K. Watanabe, T. Jwai, J. El. Micr. 4, No. 3, 37, 1956 (in Japanese).
12. N. Uyeda, E. Suito, J. El. Micr. 4, 36, 1956 (in English).
13. Y. Naito, S. Takahashi, J. El. Micr. 3, No. 3, 26, 1954 (in Japanese).
14. H. Noake, S. Hirota, Y. Mizushima, J. El. Micr. 4, 50, 1956 (in English).

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