Influence of large angle polepiece on spherical aberration coefficient.

X-rays, secondary electrons, and other emitted electrons need to be extracted at a large solid angle to enhance electron collection efficiency in transmission electron microscopy. The finite element method is employed to investigate the effects of different polepiece angles on the spherical aberration coefficient of polepiece. The research findings reveal that the azimuthal angle β of the upper polepiece has a substantial effect on the spherical aberration coefficient. When β = 30°, the minimum spherical aberration coefficient is achieved. When β ≥ 50°, the spherical aberration coefficient increases significantly, which adversely affects imaging. The aperture size of the upper polepiece has a relatively minor effect on the spherical aberration. The design of the large-angle polepiece offers novel design concepts for future emission X-ray/electron collection devices, while also offering a new reference for the design of objective lenses in transmission electron microscopy.