GB1116442A - Improvements in or relating to particle accelerating tubes - Google Patents

Abstract

1,116,442. Particle accelerators. UNITED KINGDOM ATOMIC ENERGY AUTHORITY 16 Nov., 1965 [19 Nov., 1965], No. 47260/64. Heading H1D. In a D.C. particle accelerator at least one " quartet" of axially localized transverse magnetic fields is provided along the acceleration tube to deflect the beam successively away from the axis of the tube, parallel to the axis, towards the axis and then along the axis again or, in practice, along a path parallel to, but slightly displaced from the axis, as shown. Spurious electrons are, however, deflected into the electrodes and the electron loading is thus reduced. The magnetic fields may be set up by one or more pairs of permanent magnets or by annular permanent magnets incorporated in selected electrodes, i.e. mounted in the dished portions of selected electrodes with coverplates provided to shield the magnets from the electric fields. At the input end of the acceleration tube electrodes with circumferentially corrugated apertures may be used to provide non-axial electric fields. Alternatively electrodes with non-corrugated circular apertures progressively decreasing in diameter may be used. In an arrangement with pairs of permanent magnets the apertures of the electrodes have enlarged end portions to aid evacuation and successive electrodes are rotated, in certain regions where the magnetic fields are closely spaced by 90 degrees, to provide optical baffling. In a second arrangement with annular magnets Fig. 7 (not shown), relatively large apertures are used to increase pumping speed. Electrodes dished in either direction relative to the beam may be used. In the arrangement shown, certain of the electrodes may be flat with a transitional degree of dishing of the electrodes on either side in order to avoid any reduction in the number of electrodes along the acceleration tube due to the incorporation of the magnets. A progressive dishing of the electrodes adjacent those carrying the magnets may also be used in the second arrangement, Fig. 7 (not shown). In the arrangement shown, successive " quartets " divert the beam to opposite sides of the tube axis. In the second arrangement, Fig. 7 (not shown), the beam is always diverted to the same side. The accelerator may be for accelerating ions or electrons.