Electron Accelerators for High-Voltage Electron Microscopy (HVEM)

1972 ◽  
Vol 30 ◽  
pp. 462-463
Author(s):  
Günter O. Reinhold
Keyword(s):  
Electron Beam ◽  
High Voltage ◽  
High Energy ◽  
Electron Gun ◽  
Resolving Power ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
Electron Microscopes ◽  
The Stability

High-voltage electron microscopes are characterized by accelerating voltages in the megavolt range (500 kV and above). Compared to conventional electron microscopes, with voltages up to 200 kV, the high-voltage instruments offer the advantage of improved resolving power (1 to 10 Å) and greater effective penetration of the electron beam. A basic difference between ordinary and high-voltage electron microscopes is the use of an electron accelerator in place of the electron gun to accelerate the electron beam to the required high energy. The resolving power of an electron microscope is determined by the stability of the accelerating voltage, the mechanical precision of the lenses and specimen stages, the stability of the lens supply current and freedom from mechanical vibrations. The symmetrical cascade generator is the only high-voltage dc power supply to meet these requirements with regard to voltage stability and vibration-free performance.

High-Voltage Electron Microscopy

1969 ◽  
Vol 2 (2) ◽  
pp. 95-133 ◽  
Author(s):  
V. E. Cosslett
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Image Intensifier ◽  
Chromatic Aberration ◽  
Biological Tissues ◽  
Electron Gun ◽  
Resolving Power ◽  
Small Aperture ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron

SummaryThe main advantage of high voltage in electron microscopy is greater penetration. When using an aperture of optimum size the thickness of specimen that can be imaged increases almost linearly with applied voltage in the case of light elements, both when the criterion is image intensity and when it is resolution. For heavy elements the increase is less rapid. With a small aperture the increase in observable thickness is still less rapid, and ‘saturates’ towards I MV. For a specimen of given thickness, image definition increases nearly linearly with voltage owing to the decrease in chromatic aberration. Although ultimate resolving power improves with voltage, the gain is slight and is offset by a fall in contrast. The optimum voltage for very high resolution is probably between 200 and 300 kV. Radiation damage arising from ionization decreases with rising voltage, making easier the examination of sensitive materials such as polymers. On the other hand, ejection of atoms by head-on collision increases rapidly above a threshold voltage, causing observable defects in metals.In construction, a high-voltage microscope differs from the normal type only in size and in having an accelerator instead of a simple electron gun. In operation it differs little, apart from precautions to avoid fiashover in the accelerator. A decrease in response of viewing screens and photographic emulsions is more than compensated by higher brightness of the electron gun. The chief applications so far of the high-voltage microscope have been for studying thick films of metals, magnetic materials, ceramics and polymers. Improved preparation techniques should make it possible to study sections of biological tissues up to 5 μ thick. The observation of micro-organisms and other specimens in the wet state can be carried out in double-walled cells, but only at poor resolution. Still higher voltages, up to 3 or MV coupled with the use of an energy analyser or an image intensifier, should improve further the microscopy of such thick specimens.

In-situ studies in the high-voltage Electron Microscope

1990 ◽  
Vol 48 (4) ◽  
pp. 504-505
Author(s):  
K.H. Westmacott
Keyword(s):  
Phase Transitions ◽  
High Voltage ◽  
Bulk Material ◽  
Outer Region ◽  
High Energy ◽  
Research Areas ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
Electron Microscopes

The principal advantages of high voltage electron microscopes are the ability to 1) attain higher resolution by virtue of the shorter wavelength, and 2) penetrate thicker specimens to observe dynamic behavior representative of bulk material. Some recent examples of in-situ HVEM research, representing the latter category, will be summarized in this contribution, and future directions discussed. Included in the most active research areas are phase transitions, deformation, high temperature reactions and environmental cell studies.Irradiation with high energy electrons in an HVEM provides a convenient alternative to thermal treatments for inducing phase transitions in alloys. An illustration of how ordering or disordering of the same material can occur under electron irradiation is shown in Figure 1. In this example, a Pt7C ordered phase was formed in a Pt-C alloy at 500°C with a defocused beam (outer region) and subsequently disordered at 30°C with a focussed beam (inner spot).

High Voltage Electron Microscopy of Muscle Using Thick Slices of Embedded Tissue and Selective Stains

1982 ◽  
Vol 40 ◽  
pp. 14-17
Author(s):  
Lee D. Peachey
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
High Energy ◽  
High Voltage Electron Microscopy ◽  
Whole Cells ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
High Energy Electrons ◽  
Critical Point Drying ◽  
Plastic Embedding

One way to take advantage of the increased penetrating power of the high energy electrons in a high voltage electron microscope for the study of biological cells and tissues is to examine thicker sections or slices of embedded tissues. Whereas a thickness of 0.1 micrometers usually is considered to be the useful limit on section thickness for electron microscopy at 100 kV, one can reasonably expect this limit to be increased ten-fold when using accelerating voltages in the range of 1000 kV. In fact, experience has shown that one can go considerably beyond this in thick ness and still get images that are useful for biological analysis. The examination of slices of tissues up to several micrometers thick offers clear advantages over the study of thinner sections in the elucidation of three-dimensionals tructure. This approach can be contrasted to the study of whole cell mounts, as discussed in other papers in this symposium. Whole cells usually are examined after critical point drying, without embedding. Such specimens, suspended in a vacuum, present little problem with respect to contrast. Embedded and sectioned tissues, however, are suspended in a plastic embedding material, which itself has considerable electron scattering power. Therefore, unless the tissue elements are well stained relative to the surrounding embedding material, their visibility and contrast can be insufficient for useful and interpretable images, especially in thick slices.

High Voltage Electron Microscopy in Biology

1970 ◽  
Vol 28 ◽  
pp. 12-13
Author(s):  
Hans Ris
Keyword(s):  
Electron Microscopy ◽  
Heavy Metal ◽  
Electron Microscope ◽  
High Voltage ◽  
Cell Structure ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Sectioning Method ◽  
High Voltage Electron ◽  
Electron Microscopes

Conventional electron microscopes operate with accelerating voltages up to 100kV. Because of the scattering of electrons by atoms of the specimen an image with reasonable resolution can only be obtained with very thin specimens. The study of cell structure with the electron microscope became possible only with the introduction of ultramicrotomes which produce sections of plastic-embedded tissues down to about 100A in thickness. It has long been known that useful images could be obtained with much thicker materials at higher accelerating voltages (cf. refs. 1 and 2) and in the early sixties electron microscopes operating at voltages of up to one million Volts were built in Japan and in France. Their capabilities were soon demonstrated in metallurgy but they were ignored until recently by biologists. For one, biologists were busy exploiting the sectioning method and in addition may have been deterred by the knowledge that scattering contrast rapidly decreases at higher accelerating voltage. Only recently has it been realized that excellent contrast is obtained at 500 and 1000kV with the usual heavy metal stains (3,4). High voltage microscopes are now manufactured commercially in England (AEI), France (GESPA) and Japan (Hitachi, Jeol) and should soon be more widely accessible.

High Resolution Electron Microscopy in Organic Chemistry: 1-MEV Electron Microscope in Kyoto

1990 ◽  
Vol 48 (1) ◽  
pp. 140-141
Author(s):  
Sakumi Moriguchi ◽  
Hiroki Kurata ◽  
Seiji Isoda ◽  
Takashi Kobayashi
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
High Voltage ◽  
Phase Transfer ◽  
High Resolution Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
Spatial Frequencies ◽  
Electron Microscopes ◽  
The Stability

Since the epock-making results of 1.5 Å point-to-point resolution obtained with the 500 kV HREM in Kyoto in 1978, we are convinced of the validty of the high voltage electron microscope for the high resolution. However, in order to attain the higher resolution of about 1.3 Å, which is required to resolve a carbon-carbon distance in an aromatic hydrocarbon, there remain so many problems to be solved. In 1990 a new 1 MeV microscope with twin-tank (JE0L-ARM1000) in top-entry type has been installed in Kyoto university aiming to achieve such high resolution.The stability of high voltage is especially important for high resolution because the energy spread of the incident electron beam attenuates the phase transfer function and reduces the image contrast in higher spatial frequencies region. In order to suppress the high voltage fluctuation lower than 1 p. p. m. at 1 MeV and to monitor it, the twin-tank system is adopted, which has produced also satisfactory results in the previous high voltage electron microscopes in Kyoto. Fig. 1 shows the stability of the high tension measured at the top of the accerelating column of the new 1 MeV microscope. The fluctuation is evidently suppressed to less than 1 × 10-6 for five minutes long. The ripple monitored on a sincroscope is also less than 1 p.p.m. The chromatic abberation constant Cc is 3.6mm.

High Voltage Electron Microscopy of Ion-Milled Dental Enamel

1974 ◽  
Vol 32 ◽  
pp. 60-61
Author(s):  
L. D. Ackerman ◽  
S. H. Y. Wei
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Third Molar ◽  
Polarized Light ◽  
Dental Enamel ◽  
Longitudinal Section ◽  
Ion Milling ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron

Mature human dental enamel has presented investigators with several difficulties in ultramicrotomy of specimens for electron microscopy due to its high degree of mineralization. This study explores the possibility of combining ion-milling and high voltage electron microscopy as a means of circumventing the problems of ultramicrotomy.A longitudinal section of an extracted human third molar was ground to a thickness of about 30 um and polarized light micrographs were taken. The specimen was attached to a single hole grid and thinned by argon-ion bombardment at 15° incidence while rotating at 15 rpm. The beam current in each of two guns was 50 μA with an accelerating voltage of 4 kV. A 20 nm carbon coating was evaporated onto the specimen to prevent an electron charge from building up during electron microscopy.

Three-Dimensional Visualization of the T-System of Frog Muscle Using High Voltage Electron Microscopy and a Lanthanum Stain

1977 ◽  
Vol 35 ◽  
pp. 570-571 ◽  
Author(s):  
Lee D. Peachey ◽  
Clara Franzini-Armstrong
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Three Dimensional ◽  
Biological Tissues ◽  
High Voltage Electron Microscopy ◽  
Transverse Tubular System ◽  
Peroxidase Reaction ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
T System

The effective study of biological tissues in thick slices of embedded material by high voltage electron microscopy (HVEM) requires highly selective staining of those structures to be visualized so that they are not hidden or obscured by other structures in the image. A tilt pair of micrographs with subsequent stereoscopic viewing can be an important aid in three-dimensional visualization of these images, once an appropriate stain has been found. The peroxidase reaction has been used for this purpose in visualizing the T-system (transverse tubular system) of frog skeletal muscle by HVEM (1). We have found infiltration with lanthanum hydroxide to be particularly useful for three-dimensional visualization of certain aspects of the structure of the T- system in skeletal muscles of the frog. Specifically, lanthanum more completely fills the lumen of the tubules and is denser than the peroxidase reaction product.

Radiation-Induced Precipitation at Thin Foil Surfaces in Ni-Be Alloys

1982 ◽  
Vol 40 ◽  
pp. 598-599
Author(s):  
T. Mukai ◽  
T. E. Mitchell
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Electron Irradiation ◽  
High Vacuum ◽  
Thin Foil ◽  
Homogeneous Precipitation ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
Radiation Induced

Radiation-induced homogeneous precipitation in Ni-Be alloys was recently observed by high voltage electron microscopy. A coupling of interstitial flux with solute Be atoms is responsible for the precipitation. The present investigation further shows that precipitation is also induced at thin foil surfaces by electron irradiation under a high vacuum.

Some Biological Applications of High Voltage Electron Microscopy

1974 ◽  
Vol 32 ◽  
pp. 298-299
Author(s):  
Hans Ris
Keyword(s):  
High Voltage ◽  
Chromosome Structure ◽  
Nerve Fibers ◽  
Good Resolution ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
University Of Wisconsin ◽  
High Voltage Electron ◽  
One Year ◽  
The University

The High Voltage Electron Microscope Laboratory at the University of Wisconsin has been in operation a little over one year. I would like to give a progress report about our experience with this new technique. The achievement of good resolution with thick specimens has been mainly exploited so far. A cold stage which will allow us to look at frozen specimens and a hydration stage are now being installed in our microscope. This will soon make it possible to study undehydrated specimens, a particularly exciting application of the high voltage microscope.Some of the problems studied at the Madison facility are: Structure of kinetoplast and flagella in trypanosomes (J. Paulin, U. of Georgia); growth cones of nerve fibers (R. Hannah, U. of Georgia Medical School); spiny dendrites in cerebellum of mouse (Scott and Guillery, Anatomy, U. of Wis.); spindle of baker's yeast (Joan Peterson, Madison) spindle of Haemanthus (A. Bajer, U. of Oregon, Eugene) chromosome structure (Hans Ris, U. of Wisconsin, Madison). Dr. Paulin and Dr. Hanna are reporting their work separately at this meeting and I shall therefore not discuss it here.

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