Side focusing fields generated by offset-pole periodic cusped magnets

Side focusing fields generated by offset-pole periodic cusped magnets for the propagation of sheet electron beams have been investigated theoretically and numerically. Increasing the offset length, decreasing the width of beam channel, or increasing the axial length of magnet poles will increase the strength of the side focusing fields, without changing their transverse gradient. Increasing the height of beam channel or the thickness of magnet poles will make the side focusing fields weaker, but of a better linearity. It is recommended that gradient match between the focusing force and the defocusing force acting on the sheet electron beam be made before the amplitude match between them for simplicity. The height of beam channel and the axial length of magnet poles should be chosen careful