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Journal Radioengineering №8 for 2016 г.
Article in number:
Design and numerical simulation of the miniature electron gun
Keywords:
auger electron spectroscopy
electron gun
angular aberration
Wehnelt cylinder
perveance
space charge
Authors:
D.Yu. Tarabrin - Ph. D. (Eng.), Senior Research Scientist, Ryazan State Radio Engineering University. E-mail: tarabrin-dmitriy@mail.ru
A.A. Trubitsyn - Dr. Sc. (Phys.-Math.), Professor, Ryazan State Radio Engineering University. E-mail: assur@bk.ru
S.B. Bimurzaev - Dr. Sc. (Phys.-Math.), Professor, Almaty University of Power Engineering & Telecommunications. E-mail: bimurzaev@mail.ru
Abstract:
The basis of modern design principles constitute the numerical methods as having the most commonality assessments and a high degree of approximation models to real objects. For the development of methods and approaches to the design of low-voltage sources of accelerated electrons necessary to use the modern optimization techniques.
According with the expressions that define angular aberration of the cathode lens, as a parameter sufficient to use the maximum value of the electric field at the emitting surface of the cathode.
Optimization results demonstrated that in the framework the investigated design cathode modulator unit with thermionic cathode ES-423E the optimal relation hole diameter in the Wehnelt cylinder to the height of the cathode landing equal to 5−6. At this ratio provides maximum brightness of the electron beam.
Allowance for the influence the space charge is an important step in the design of cathode-ray devices. Numerical analysis has shown that at emission current density of 30 A/cm2 and an accelerating voltage of 5 kV space charge can be neglected. Distortion of the electric field is not greater than 10−2%.
Three single electrostatic lens is used to transfer images crossover on a target. Two lenses are short focus decreases, and the lens at the gun output is long focus transporting the electronic image on the specimen at a distance of not less than 20 mm. Before each focusing diaphragming of the electron beam to reduce the angular spread is produced. The diaphragms are placed in front of the lens entrance, where the electron beam is greatly defocused.
As a result, numerical optimization found the electronic configuration of the electron gun, providing the ultimate brightness of the electron beam. Focus system and the electron beam on the target transport can provide a focal spot diameter of about 1 microns at a current of 220 nA. Developed a miniature electron gun can be used as focused electron source embedded in an axially symmetric energy analyzers.
Pages: 160-168
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