Patent ID: 8829462
Filing Date: 2014-09-09
Classification: H01F,H05H

Abstract:
1. A multipole magnet for deflecting a beam of charged particles, comprising: a plurality of ferromagnetic poles arranged in a pole plane; a plurality of permanent magnets each having a magnetisation direction, and each being arranged to supply magnetomotive force to the plurality of ferromagnetic poles to produce a magnetic field along the pole plane in a beamline space between the poles; and a plurality of ferromagnetic flux conducting members arranged to channel magnetic flux from at least one of the plurality of permanent magnets; wherein the multipole magnet comprises an even number of ferromagnetic poles, each pole being arranged to diametrically oppose another of the poles in the pole plane along a pole axis, wherein each of the plurality of permanent magnets is associated with at least one of the plurality of poles and the magnetisation direction of each permanent magnet is orientated in the pole plane at an angle between 45° and 135° relative to the pole axis of the associated pole, and each of the plurality of permanent magnets is associated with one of the plurality of poles; and at least some of the ferromagnetic flux conducting members comprise ferromagnetic bridges that channel magnetic flux between the permanent magnets of two adjacent poles.