UDC 621.386.22
LIMIT ESTIMATES OF MINIMUM FOCAL SPOT SIZES IN MICROFOCUS X-RAY TUBES
E. A. Kozlov, PhD (in technical sciences), associate professor, department of industrial electronics, RSREU, Ryazan, Russia;
orcid.org/0000-0003-2038-6732, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
A. A. Trubitsyn, Doctor in Physics and Mathematics, full professor, department of industrial electronics, RSREU, Ryazan, Russia;
orcid.org/0000-0002-9337-8947, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
E. Yu. Grachev, PhD (in technical sciences), associate professor, department of industrial electronics, RSREU, Ryazan, Russia;
orcid.org/0000-0001-7813-7769, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
The paper presents a theoretical analysis of maximum achievable focal spot size in microfocus X-ray tubes. The aim of the work is to determine theoretical limits of focal spot size reduction in microfocus X-ray tubes taking into account the influence of electron beam parameters (current, brightness) and spheri cal aberration of magnetic objective lens. Analytical dependences of focal spot diameter on the angle of con vergence of electron beam, brightness, spherical aberration coefficient, and the focal length of magnetic lens are established. The authors show that the use of modern cathodes (LaB6, Schottky) and magnetic lenses with a radial gap makes it possible to achieve submicron sizes of the focal spot (0,1 – 1 μm). The results of the work are important for the development of domestic X-ray systems of nondestructive testing and mi crotomography, providing competitiveness with foreign analogs.
Key words: : microfocus X-ray tube, focal spot diameter, electron optical brightness, spherical aberration, cathodes, magnetic lenses.