A double pole-gap design for low spherical aberration in thin solenoids

We here report a new design of a double air-slot or pole-gap type, axially thin, shielded solenoid with lower spherical aberration than conventional single pole-gap type solenoids. The net on-axis field from two optimally distanced pole gaps reduces the spherical aberration. The working principle of the model is also given by a pair of coaxial, in-air, identical current loops which can have lower spherical aberration than a single current loop. The new design is useful to achieve low spherical aberration in axially thin shielded solenoids.