(57) The electrons emitted from a cylindrical cathode (1) by the method as per this present
invention are formed in the electric field at the cathode into a beam with divergent
paths being on the surface of coaxial cones the apex angles whereof are contained
in an interval varying within the limits of 0-0.5 radian around their central angle
(15) of 0.1-1.5 radians. Next, electrons with a narrow energy interval are separated
from the beam by means of a cylindrical mirror analyser (4, 7) after curving the electron
paths therein and selecting them with the application of slits (8, 9). These electrons
are then converged in a set of electron lenses (117).
The electron gun has a cylindrical cathode (1) having a part of the surface in the
form of a 0.01-10 mm wide ring coated with emission paste (2). Electrodes (4, 7) of
the cylindrical narrow analyser are mounted around the cathode (1). An inlet slit
(5) of the internal electrode (4) is shifted horizontally in relation to the active
cathode surface coated with emission paste (2) so that the angle between the electron
beam in the region of that slit (5) and the axis (0) of the system is contained within
an interval of 0-0.5 radian around their central angle (15) of 0.1-1.5 radians.
The electron gun comprises an electrode (12) placed between the analyser (4, 7) and
the set of electron lenses (11) and co-forming equipotential lines (10) with a coaxial
circular ring-shaped slit (9).
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