GB1269017A - Electron beam deflector system - Google Patents

Abstract

1,269,017. Particle accelerators. THOMSON C.S.F. 3 March, 1970 [12 March, 1969], No. 10215/70. Heading H1D. The electron beam emerging from a particle accelerator passes through a first deflecting means Dl, Fig. 1, which deflects the beam through an angle of, for example, 37 degrees, and through a second deflecting means D2 adapted to produce a deflection in the same plane of, for example, 127 degrees so that the final path intersects the original path preferably at a right angle. The first deflection means Dl is achromatic and comprises three electromagnets with sector shaped polepieces arranged as shown. The edge of each polepiece may be defined by a rotatable semicircular member (Fig. 3, not shown) so that the angle it makes with the beam may be varied. The second deflection means may comprise a single electromagnet E4 with sector shaped polepieces, the end faces of which are inclined at 35 degrees to the normal to the beam path (Fig. 4, not shown). The opposed faces of the polepieces are preferably inclined to each other so that the index n = 0À5 where where B is the flux and R the radius of the particle trajectory; this gives identical convergence properties in two planes. The deflection means D2 may be followed by three quadruple lenses which are successively convergent, divergent and convergent so that the output beam may be focused to a circular cross-section (Fig. 5, not shown). Alternatively the polepieces of the magnet E4 may comprise a first section with n = 0À5 and a second section with a negative field gradient where n = 2 or 3 (Fig. 6, not shown); the entry face is normal to the beam whereas the exit face is inclined at a variable angle. The beam may pass through scanning means in the form of four coils and associated polepieces which taper conically along the beam path (Fig. 7, not shown), Alternatively a scanning coil may be associated with magnet E4 for scanning in one direction, and an additional electromagnet may be provided adjacent deflection means D1 for scanning in the other direction (Fig. 8, not shown). The system is rotatable about the axis X-X<SP>1</SP>.