Patent ID: 8089050

Claim:
A method of modifying a ribbon-shaped ion beam having an elongate cross-section normal to a beam direction, wherein at any position along said ribbon-shaped beam an orthogonal (x, y, z) Cartesian co-ordinate system is defined in which a z-axis of the co-ordinate system extends in the beam direction at a center line of said ribbon-shaped beam, an x-axis extends in a long direction of said elongate cross-section of said ribbon-shaped beam, and a y-axis extends in a short direction of said elongate cross-section, the method comprising the steps of: providing opposed ferromagnetic bars each having a length and defining between them an elongate open space to accommodate said ribbon-shaped beam passing between the bars with the x-axis of the beam extending along a length of said elongate space; providing, on each of said opposed ferromagnetic bars, a respective first coil structure comprising a continuous winding which has a first predetermined distribution along said length of the bar of turns per unit of length, said first predetermined distribution being selected to provide, when said first coil structures are selectively energized, a first component magnetic field in a y-direction in said elongate open space between said opposed ferromagnetic bars, said first component magnetic field having a corresponding first distribution of magnetic field intensity over said length of said open space in an x-direction; providing, on each of said opposed ferromagnetic bars, at least a respective second coil structure comprising at least one continuous winding which has a second predetermined distribution along said length of the bar of turns per unit length, said second predetermined distribution being selected to provide, when said second coil structures are selectively energized, a second component magnetic field in said y-direction in said elongate open space between said opposed ferromagnetic bars, said second component magnetic field having a corresponding second distribution of magnetic field intensity over at least a part of said length of said open space in said x-direction; and passing said ribbon-shaped beam through said elongate open space between said opposed ferromagnetic bars; and selectively energizing said respective first and second coil structures with electric currents to apply a desired modification to said ribbon-shaped ion beam.