GB1180013A - Improvements relating to Electron or Ion Guns. - Google Patents

Abstract

1,180,013. Electron guns; ion sources. ELECTRIC & MUSICAL INDUSTRIES Ltd. 8 Feb., 1967 [15 Feb., 1966], No. 6480/66. Heading H1D. An electron or ion gun includes a collimator electrode 3 in the form of a bundle of tubes through which the beam passes, the length of each of the tubes being at least equal to five times its maximum cross-sectional dimension, whereby electrons or ions having appreciable lateral velocities are removed from the beam. In the electron gun shown the anode 5 forms with the collimator electrode 3 a diverging lens, aberrations due to which may be reduced by choice of a non-planar shape for the exit surface of electrode 3. The tubes forming the collimator electrode may either be parallel, or cone-shaped either converging or diverging towards the cathode (Fig. 2, not shown), the electrode as a whole being mounted within a further, cylindrical electrode, between which and the cathode is disposed an apertured diaphragm or mesh electrode for enhancing control of the beam shape and current. In further arrangements, the collimator electrode is so disposed within an outer electrode that both its ends are situated in substantially field-free regions (Figs. 6 and 7, not shown), or a strong converging field is set up at its output end to produce a beam cross-over thereafter (Figs. 8a and 8b, not shown). The collimator electrode may be formed of a plurality of nickel tubes, a drilled solid block, or corrugated sheets joined to produce an array of holes. The electrode may be employed in the gun of an oscilloscope, electron microscope, electron machining device, or television pick-up tube; when employed in an infra-red camera tube, the central tubes of the bundle may be obturated, to protect the target from radiation from the cathode.