Abstract: A permanent magnetic structure comprising a cylindrical body (15) and a termination structure (14, 12, 10). The cylindrical body (15) is composed of magnetic material causing a magnetic field and flux of magnetic induction. The cylindrical body (15) is oriented such that the interface between the cylindrical body 15 and the termination (14, 12, 10) is parallel to the magnetic induction and the cylindrical body (15).