GB768175A - Improvements in or relating to cathode-ray tubes employing ion traps - Google Patents

Abstract

768,175. Ion trapping in cathode ray tubes. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Dec. 10, 1954 [Dec. 15, 1953], No. 35813/54. Class 39(1). A cathode ray image reproducing tube for oscillography or television has an ion trap gun comprising at least a cathode control electrode, tubular anode and at least one electrode between the anode and the control electrode, the gun axis coinciding with the tube axis, an electrostatic field having a transverse component is set up between the anode and the electrode preceding it, wherein the cross sections of the anode are asymmetrical figures with respect to lines parallel to the plane of intersection of plane Y (at right angles to the plane X of deflection of the ions) and the plane of the paper in Figs. 2 and 3 in such a manner that the length inside the anode of the line of intersection of plane X and the plane of the paper in Figs. 2 and 3 is divided by the point P of intersection with the axis into two parts of different length of which the larger part is located on that side to which the ions are to be deflected i.e. p>q (see Fig. 5), the asymmetrical part of the anode lying at that end of the anode which is nearer to the cathode and extends over a length at least equal to the diameter of the anode aperture at that end, i.e. h# d (over part 24 in Fig. 5). The electrons can thus be made to emerge from the ion trap along the tube axis without the necessity of employing two oppositely directed magnetic deflecting fields. The anode and preceding electrode have inclined ends as shown in Fig. 5 to set up the transverse electrostatic field component, or only the anode may have inclined end, Fig. 4. The anode cross section may be flattened on the side opposite the impact point of the ions, Fig. 2, or in Fig. 3, parts 16, 17 are cylindrical but not coaxial, 16 being struck by ions. In Fig. 4 the anode has a part conical wall 18. In Fig. 5 the anode has a cylindrical part 23 and a conical part 24. The ion trap magnets are adjustable. The anode may have a straight end surface if the end of the preceding electrode is started. The tube has electromagnetic scanning coils.