The Physics
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Voltage of an Electron Microscope

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Bibliographic Entry Result
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Tipler, Paul A. College Physics. New York: Worth, 1987: 776. "The energy of the electrons is typically 100 keV" 100 kV
"Electron Microscope." Microsoft Encarta Encyclopedia 99. 1999 ed. CD-ROM. Microsoft, 1998. "A high voltage electric field (50,000 to 100,000 volts) applied between a pair of metal plates accelerates the electrons, and electric or magnetic lenses condense the electrons into a narrow beam." 50–100 kV
Perkins, G., Renken, C., Martone, M., Young, S., Ellisman, M. & Frey, T. Electron Tomography of Neuronal Mitochondria: Three-Dimensional Structure and Organization of Cristae and Membrane Contacts. Journal of Structural Biology. 119 (1997):260-272. (National Center for Microscopy and Imaging Research Journal Covers.) "Three-dimensional reconstructions of representative mitochondria were made from single-axis tilt series acquired with an intermediate voltage electron microscope (400 kV)" 400 kV
Hillier, James. "Electron Microscope." Collier's Encyclopedia.1968 ed. Vol. 9 Crowell-Collier, 1968: 18-21. "This potential is usually in the range of 30 to 80 kV, though in some special instruments potentials as high as 300 kV have been used." 30–80 kV
300 kV
Features of 3 MV Ultrahigh Voltage Electron Microscope. Osaka University. "In June 1995, the installation of an electron microscope with the world's highest routine acceleration voltage of 3 million volts has been completed in the Research Center….
Normal Standard: 3.0 MV
Intermediate Standard: 0.5, 1.0, 1.5, 2.0, 2.5 MV
Maximum: 3.5 MV"
3000 kV

An electron microscope is an instrument that uses a beam of energetic electrons to highly magnify and observe objects. By the 1930s, knowledge of the wave properties of particles led to the development of the electron microscope. There are two types of electron microscopes, the Transmission Electron Microscope (TEM), and the Scanning Electron Microscope (SEM). Due to electrons' extremely short wavelength, these microscopes can be used to study a sample's crystallographic information, topography, morphology, and composition.

Electron microscopes work in the following way. An electron source produces the electrons. A positive electric potential is used to accelerate the electrons in the direction of the sample. Electric potential or voltage (V) measured it volts (V), is the work done in moving a charge between two points in an electric field. Using electric or magnetic lenses, a cluster of electrons is transformed into a thin beam. This beam of electrons is then focused on the sample with the use of magnetic lenses. When the highly energetic electrons reach the sample, various reactions occur. These reactions are detected and changed into a very fine and detailed image.

In a typical electron microscope, an acceleration voltage is used in the range of one hundred thousand to a few million volts. In June 1995, Osaka University, Japan, the world's highest voltage of 3,000 kV was applied. There are advantages of ultrahigh voltage electron microscopes over conventional electron microscopes. The high voltage electrons have more penetrating power and a very high resolution of down to a tenth of a nanometer can be reached.

Sabrina Khan -- 2001