Computed laminography (CL) technology can conduct high-precision non-destructive testing of large-size plate components. The extremely high precision requirements of the sample stage result in expensive equipment, being limited by the brightness of X-rays, and small scanning speed, which are not conducive to the promotion of the application. Based on the above limitations, a high-speed scanning micro-focus X-ray source for ring targets is proposed, which generates a micro-focus X-ray source with circular trajectory motion through rapid scanning of a ring target by an electron beam and can substantially improve the sample inspection efficiency. But the electron beam will produce deflection aberration during scanning leading to aberrations, and it is necessary to utilize an aberration correction system while constraining the deflection angle to maintain the beam spot size and shape of the electron beam.

In this paper, based on the theory of electron optics, the effects of aberration, working distance, and scanning range on the beam spot size and shape during the scanning process of the electron beam are theoretically analyzed, and then the physical model of the ring target high-speed scanning micro-focus X-ray source is established based on the electron optical calculation software of Munro’s Electron Beam Software (MEBS). Then, the physical model of the ring target high-speed scanning micro-focus X-ray source is established based on MEBS, and the minimum beam spot size corresponding to the absence of the scanning field at different working distances, as well as the beam spot sizes at the farthest edge of the scanning field at different working distances, scanning ranges and aberration correction systems is calculated. Finally, based on the analysis of the calculation results, the maximum deflection range that can guarantee the spot size and shape of the electron beams at different working distances, and the effects of different aberration correction systems on the spot size and properties at the farthest edge of the deflection field are given.

Under the same working distance, as the scanning range increases, the degree of beam spot ellipticity becomes larger (Fig. 7); under the same scanning range, as the working distance increases, the degree of beam spot ellipticity becomes smaller (Fig. 8). For different scanning ranges, there exists a critical working distance, and within this scanning range, the beam spot size and shape of the electron beam do not change much. When a scanning range and a working distance are converted into a scanning angle, there exists a relatively optimal critical scanning angle of about 2.87° (0.05 rad), less than which the deflected beam spot aberration is small. After using the aberration correction system, the quality of the beam spot at different deflection ranges and working distances is significantly improved, and the corresponding scanning angle is increased to some extent (Table 3).

This paper presents theoretical analysis and simulation work on the electron optics of a micro-focus X-ray source for high-speed scanning of ring targets. The relationship among the beam spot size and shape, the working distance, and scanning range is revealed, and the relatively optimal critical scanning angle is about 2.87° (0.05 rad), in which the spot size and shape of the electron beam can be guaranteed to be basically unchanged. After the aberration correction, this scanning range is increased to some extent. This work provides a theoretical reference for the designs of the electron beam control system and target material in the ring target high-speed scanning microfocus X-ray source and confirms the feasibility and great potential of the static high-speed CL scanning system based on the ring target. In future work, the design will be further optimized by combining the existing calculation model, the existing micro-focus X-ray source prototype will be modified, and experiments will be designed for validation, which will bring its real application in nondestructive testing scenarios of plate components.