GB893079A - Trochotron tube - Google Patents

Abstract

893,079. Electron beam apparatus. BURROUGHS CORPORATION. Dec. 15, 1960 [Dec. 21, 1959; July 18, 1960], No. 43217/60. Class 39(1) In a trochotron type multi-position beam switching tube the axial magnetic field is set up by a pair of disc shaped permanent magnets 52, 58, Fig. 1, positioned at opposite ends of the electrode assembly. The magnets are mounted on rods 64 extending through the mica end discs 22, 24 and the electrode leads 50 are either bent around the edge of the lower, disc magnet 58, Fig. 4 (not shown), or, as shown, coated with insulating material and passed through apertures in the magnet. The magnets may be of insulating material in which case the electrode leads are uninsulated and may be used as electrode supports in place of the mica discs. A magnetic shield 90 is stuck on or clamped to the envelope 10. In another embodiment Fig. 5 (not shown) the shield comprises the tube envelope, the upper and lower ends of the envelope being formed by the permanent magnet discs. The shield portion of the envelope may consist of soft iron or of a material whose permeability decreases with increase of temperature in order to compensate the opposite effect in the magnet discs where these consist of ferrite material. In Fig. 6 the magnetic path between the magnet discs 104<SP>1</SP>, 106<SP>1</SP> and the shield portion 102 of the envelope is interrupted by spacer rings 114, 116 of glass or a metal having a low permeability in order to provide a magnetic field shown by dashed lines 117 which is weaker in the centre of the electrode assembly than at the ends is stated to aid the electron flow. The tube pins 108 are sealed in the spacer ring 114. In Fig. 8 the envelope .120 is cup-shaped, the upper magnet 104<SP>11</SP> is secured to end wall 122, and the lower magnet 106<SP>11</SP> is secured to a header 124 which is a plate of the same material as the envelope 120.