Method and apparatus for generation of a uniform-profile particle beam

A method of generating a particle beam having a uniform profile in a predetermined plane, said method comprising:

• inducing emission of charged particles from a charged particle emitter;
• accelerating said charged particles along a central beam axis toward a planar radiation-generating target screen using a plurality of anodes, said target screen comprising a planar surface orthogonal to said central beam axis;
• generating a magnetic field with a first magnetic element, wherein an axis from one pole of said first magnetic element to the opposite pole of said first magnetic element is aligned with said central beam axis within an angular range of less than 30 degrees, and wherein said first magnetic element is at the surface of said charged particle emitter that is opposite the surface of said charged particle emitter from which said charged particles are emitted, wherein said magnetic field has a different strength at said predetermined plane than at said charged particle emitter;
• modifying a beam profile of said charged particles;
• and
• generating a magnetic field at and around said target screen with a second magnetic element that is positioned adjacent to and around the perimeter of said target screen, wherein a plane coincident with said planar surface of said target screen and extending outside said perimeter of said planar surface of said target screen would pass through said second magnetic element, and wherein the polarity of said first magnetic element is opposite the polarity of said second magnetic element so that the directions of the magnetic fields of said first and second magnetic elements along said central beam axis are opposite to one another.