A magnet pole for a cyclotron comprising at least 3 hill sectors and a same number of valley sectors comprising a bottom surface , said hill sectors and valley sectors being alternatively distributed around a central axis, Z, each hill sector comprising: (a) an upper surface defined by: - an upper peripheral edge , said upper peripheral edge being bounded by a first and a second upper distal ends , and being defined as the edge of the upper surface located furthest from the central axis; - an upper central edge , said upper central edge being bounded by a first and a second upper proximal ends and being defined as the edge of the upper surface located closest from the central axis; - a first upper lateral edge connecting the first upper distal end and first upper proximal end; - a second upper lateral edge connecting the second upper distal end and second upper proximal end; (b) a first and second lateral surfaces each extending transversally from the first and second upper lateral edges, to the bottom surfaces of the corresponding valley sectors located on either sides of a hill sector, thus defining a first and second lower lateral edges as the edges intersecting a lateral surface with an adjacent bottom surface, said first and second lower lateral edges each having a lower distal end located furthest from the central axis; (c) a peripheral surface extending from the upper peripheral edge to a lower peripheral line defined as the segment bounded by the lower distal ends of the first and second lower lateral edges; wherein the upper peripheral edge of at least one hill sector comprises a concave portion with respect to the central axis defining a recess extending at least partially over a portion of the peripheral surface of the corresponding hill sector, characterised in that , the recess is generally wedge shaped with a first and second converging lines extending away from the upper peripheral edge, with a converging angle, θ, comprised between 70° and 130°. (a) an upper surface defined by: - an upper peripheral edge , said upper peripheral edge being bounded by a first and a second upper distal ends , and being defined as the edge of the upper surface located furthest from the central axis; - an upper central edge , said upper central edge being bounded by a first and a second upper proximal ends and being defined as the edge of the upper surface located closest from the central axis; - a first upper lateral edge connecting the first upper distal end and first upper proximal end; - a second upper lateral edge connecting the second upper distal end and second upper proximal end; - an upper peripheral edge , said upper peripheral edge being bounded by a first and a second upper distal ends , and being defined as the edge of the upper surface located furthest from the central axis; - an upper central edge , said upper central edge being bounded by a first and a second upper proximal ends and being defined as the edge of the upper surface located closest from the central axis; - a first upper lateral edge connecting the first upper distal end and first upper proximal end; - a second upper lateral edge connecting the second upper distal end and second upper proximal end; (b) a first and second lateral surfaces each extending transversally from the first and second upper lateral edges, to the bottom surfaces of the corresponding valley sectors located on either sides of a hill sector, thus defining a first and second lower lateral edges as the edges intersecting a lateral surface with an adjacent bottom surface, said first and second lower lateral edges each having a lower distal end located furthest from the central axis; (c) a peripheral surface extending from the upper peripheral edge to a lower peripheral line defined as the segment bounded by the lower distal ends of the first and second lower lateral edges; <EOS>