Physical Principles of Electron Microscopy: An Introduction to TEM ...

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Chapter 1
hydrated. But high-energy electrons are a form of ionizing radiation, similar
to x-rays or gamma rays in their ability to ionize atoms and produce
irreversible chemical changes. In fact, a focused beam of electrons
represents a radiation flux comparable to that at the center of an exploding
nuclear weapon. Not surprisingly, therefore, it was found that TEM
observation kills living tissue in much less time than needed to record a
high-resolution image.
Figure 1-13. A 3 MV HVEM constructed at the C.N.R.S. Laboratories in Toulouse and in
operation by 1970. To focus the high-energy electrons, large-diameter lenses were required,
and the TEM column became so high that long control rods were needed between the operator
and the moving parts (for example, to provide specimen motion). Courtesy of G. Dupouy,
personal communication.