Patent Number: 050341839
Section: claims

1. An apparatus for producing a self-colliding charged particle beam comprising: magnetic focusing means for producing a ring-shaped magnetic field symmetrically spaced about an axis such that the magnetic field in a median plane perpendicular to said axis in the region across said ring-shaped field is unidirectional in a first direction parallel to said axis, and wherein said field is nonuniform with axial components in said first direction and radial components directed toward and away from said axis in the region above the below said plane such that the magnetic field strength of said field increases from substantially zero to some maximum value and then decreases to substantially zero as the radial distance between said field and said axis increases, said magnetic focusing means including fist, second, third and fourth concentric coils mounted coaxially with said axis, said first and second coils of substantially equal size spaced equally on either side of said median plane and magnetically polarized in said first direction, said third and fourth coils of substantially equal size to each other and of a smaller diameter than the diameters of said first and second coils, said third and fourth coils equally spaced on either side of said median plane and being magnetically polarized in the opposite direction to the polarization direction of said first and second coils; and  particle beam means including a plurality of high-velocity, charged particles having orbits that intersect said plane, said axis and said ring-shaped magnetic field, sand wherein said charged particles travel radially away from said axis in in substantially straight lines, interact with said axial components to curve as they traverse said field, and then travel radially toward said axis in substantially straight lines, and wherein particles traversing said field above and below said plane and having velocities in a predetermined range are focused axially into said median plane by said radial components and particles having velocities outside said range are defocused axially away from said median plane by said radial components.  forming a ring-shaped magnetic field symmetrically spaced about an axis with first, second, third and fourth concentric coils mounted coaxially with said axis, said first and second coils of substantially equal size magnetically polarized in a first axial direction and spaced equally on either side of a median plane perpendicular to said axis, said third and fourth coils of substantially equal size and of a smaller diameter than the diameters of said first and second coils, said third and four coils equally spaced on either side of said median plane and being magnetically polarized in the opposite direction to the polarization direction of said first and second coils such that the magnetic field in said median plane is substantially zero in the region of said axis and in the region across said ring-shaped field is unidirectional in said first axial direction, and wherein said field is nonuniform with axial components in said first axial direction and radial components in the region above and below said plane such that the magnetic field strength of said field increases from substantially zero to some maximum value and then decreases to substantially zero as the radial distance between said field and said axis increases;  directing a plurality of high-velocity, charged particles in substantially straight, radial lines from said axis toward said ring-shaped field;  causing said particles to interact with said axial components and curve as they traverse said field;  causing said particles to interact with said radial components such that particles traversing said ring-shaped field above and below said median plane and having velocities in a predetermined range are focused axially toward said median plane by said radial components and particles having velocities outside said range are defocused axially away from said median plane by said radial components; and  causing said particles to leave said field and travel radially toward said axis in substantially straight lines. 2. A method of producing a self-colliding charged particle beam comprising: