A CATHODE RAY TUBE

摘要

The deflection units, when energised, produce dynamic multipole fields which are strongly modulated. Such modulation may be achieved by the use of static magnetic multipole arrangements, since a static n-pole magnetic field simulates, for a charged particle passing eccentrically through it, a dynamic (n-2) pole field. A deflection unit has field coils and line coils, includes a static 8-pole field produced by two tangentially magnetised magnets and four radially magnetised magnets. Higher and lower order multipole fields may be suppressed by suitable dimensioning and shaping of the magnets. The permanent magnet device has an annular member of permanent magnetisable material which is provided coaxially with the longitudinal axis of the unit.