Practical Electron Microscopy and Database

The electromagnetic lenses in electron microscopes can be used to focus them into very small probe diameter (1 nm or even 0.1 nm) or to produce a electron image of the specimen, with a spatial resolution down to atomic dimensions in TEM systems. The focusing properties of a lens may be given in terms of a parameter k²,
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where,
        B_m -- The maximum value of the magnetic induction between the polepieces.
        l -- A length characteristic of the lens, which can be the half-width of the axial magnetic field distribution, or the polepiece gap S or the radius R of the bore through polepieces.
        K -- A numerical factor incorporating the charge and mass of the electron.
        V_r -- The relativistically corrected value of the electron beam voltage.