Effect of Triple-Ring Electronic Focusing Structure on the Anode Focal Spot of X-ray Sources

This is the authors' abstract. We don't add key points for this paper.

The size of the anode focal spot is a key factor in determining the imaging resolution of an X-ray source. To address the issue of unstable focal spot size caused by beam current variations over a wide operating voltage range in simple focusing structures, this paper proposes and investigates a three-ring electrostatic focusing structure that allows control of the electron beam trajectory through independent electrodes. By combining theoretical analysis and numerical simulation, the study systematically explores the effects of ring spacing, ring aperture, and focusing electrode voltage on the electron beam convergence behavior in the three-ring structure. Simulation results indicate that ring spacing and ring aperture significantly influence focusing symmetry and focal spot position, and a minimum focal spot can be achieved when the focusing electrode voltage is 2000 ± 20 V. Further experimental validation shows that under a focusing voltage of 2450 ± 20 V with ring 1 grounded, the measured anode focal spot size is 26.6 μ m × 19 μm, consistent with simulation trends, confirming the feasibility and stability of the three-ring focusing structure. The findings provide a theoretical basis and parameter tuning strategy for the optimized design of micro-focus X-ray source focusing systems.