GB730862A - Improvements in or relating to vacuum discharge tubes - Google Patents

Abstract

730,862. Discharge apparatus. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Nov. 30, 1951 [Dec. 4, 1950], No. 28156/51. Class 39 (1). A high-vacuum rectifier tube comprising an insulator on opposite sides of which are disposed in intimate contact therewith a coldcathode electrode and an anode electrode is characterized in that at least one line of contact between the cathode electrode and the insulator surface is opposite the anode electrode, the anode electrode and the insulator extending on either side of said line or lines of contact. In one form, Fig. 3, the tube comprises a rod anode 2 surrounded by a glass layer 3 on which is mounted a cathode in the form of a plurality of metal rings 4, this arrangement being surrounded by an auxiliary electrode 5 which may function as an auxiliary anode or as a control grid. The construction is such that the field intensity on a line of contact between the cathode and the insulator surface is higher than that on a contact line between the anode and the insulator surface so if the potential difference between the cathode and anode is high enough the cathode gives a field emission along the line of contact with the insulator surface. The electrons emitted, in attempting to follow the lines of force through the insulator, strike the insulator and thus give rise to secondary electrons which themselves, on their way to the anode, give rise to further secondary electrons from the insulator surface. This action proceeds until the anode surface, projecting beyond the insulator, is reached. If the electrode 5 is made an auxiliary anode, the electrons divide up between the main and auxiliary anodes according to the potential which is applied to these electrodes. In a simplified construction, the auxiliary electrode 5 is omitted and the cathode is a single metal ring which in a modified construction is extended together with the glass layer 3 to enclose the free end of the rod anode. In the construction shown in Fig. 5 the cathode is in the form of a plurality of strips 6 joined at one end by a ring. In a further construction the cathode is a wire helix. In the planar arrangement shown in Fig. 7 the cathode comprises a plurality of parallel strips 11 joined at one end and separated by a glass plate 10 from one side of a plate anode 9 which has a similar cathode and glass plate mounted on its other side.