GB833031A - Electron guns - Google Patents

Abstract

833,031. Velocity modulated tubes. SPERRY RAND CORPORATION. March 22, 1957 March 28, 1956], No. 9482/57. Class 39(1). In a high power klystron or travelling wave tube having a high density beam the cathode, ring focusing electrode and accelerating anode of the gun may serve as a cavity resonator excited by the beam and producing spurious velocity modulation thereof which may be within the operating band of the tube; to prevent this the focusing electrode is formed with one or more slots extending perpendicular to the beam axis so as to interrupt the current paths of a (TM) mode of this resonator (the current paths of some TM modes normally being parallel to the electron path and the parts of the focusing electrode on either side of the slot or slots being at the same DC potential). The TMo1 and TMo2 modes are instanced. There may be four slots 23 separated by necks 24 or if the capacity of the slots is such that currents still flow the slots are filled with lossy material such as porous ceramic impregnated with carbon or the focusing electrode may be in two completely separated parts with external insulating means supporting one from the other but the two parts of the focusing electrode are still at the same DC. potential (i.e. are electrically connected together). The slots may be positioned in a region of maximum current flow in the resonator. The concave emissive cathode surface is carried from casing 14 by supports 12, 13 and has a heater 15, and the focusing electrode 18 is connected to the emissive cathode surface. The electrode 18 has flanges 19, 21, the inner diameter of flange 19 being equal to the outer diameter of the cathode and the inner diameter of flange 21 being slightly less than that of 19 but greater than that of anode 16. The flange 21 is thickened to withstand high temperatures and rounded to prevent breakdown.