Abstract: The subject matter described herein generally relates to apparatus, systems, methods and associated computer instructions for predicting the end of service life of a space charge limited vacuum electron device. The device produces an electron beam current and has a cathode and a filament powered by an adjustable voltage power supply providing a voltage between a first low voltage and a second higher voltage to heat the cathode to an electron emitting temperature. The process includes periodically, while the device is in operation, adjusting the voltage provided by the power supply while monitoring the beam current, determining a knee-point in the voltage where the beam current begins to decrease as the voltage is decreased, and calculating, based on the determined knee-point and a predetermined voltage vs service life remaining relationship, the amount of service life left in the device.

Abstract: The subject matter described herein generally relates to apparatus, systems, methods and associated computer instructions for predicting the end of service life of a space charge limited vacuum electron device. The device produces an electron beam current and has a cathode and a filament powered by an adjustable voltage power supply providing a voltage between a first low voltage and a second higher voltage to heat the cathode to an electron emitting temperature. The process includes periodically, while the device is in operation, adjusting the voltage provided by the power supply while monitoring the beam current, determining a knee-point in the voltage where the beam current begins to decrease as the voltage is decreased, and calculating, based on the determined knee-point and a predetermined voltage vs service life remaining relationship, the amount of service life left in the device.

Abstract: A photoelectric cathode has a work function lowering material such as cesium placed into an enclosure which couples a thermal energy from a heater to the work function lowering material. The enclosure directs the work function lowering material in vapor form through a low diffusion layer, through a free space layer, and through a uniform porosity layer, one side of which also forms a photoelectric cathode surface. The low diffusion layer may be formed from sintered powdered metal, such as tungsten, and the uniform porosity layer may be formed from wires which are sintered together to form pores between the wires which are continuous from the a back surface to a front surface which is also the photoelectric surface.

Abstract: A porous cathode structure is fabricated from a plurality of wires which are placed in proximity to each other in elevated temperature and pressure for a sintering time. The sintering process produces the porous cathode structure which may be divided into a plurality of individual porous cathodes, one of which may be placed into a dispenser cathode support which includes a cavity for containing a work function reduction material such as BaO, CaO, and Al2O3. The work function reduction material migrates through the pores of the porous cathode from a work replenishment surface adjacent to the cavity of the dispenser cathode support to an emitting cathode surface, thereby providing a dispenser cathode which has a uniform work function and therefore a uniform electron emission.

Abstract: A plurality of high atomic number wires are sintered together to form a porous rod that is parted into porous disks which will be used as x-ray targets. A thermally conductive material is introduced into the pores of the rod, and when a stream of electrons impinges on the sintered wire target and generates x-rays, the heat generated by the impinging x-rays is removed by the thermally conductive material interspersed in the pores of the wires.

Abstract: A reservoir dispenser cathode structure having improved thermal efficiency is provided by inner and outer subassemblies. The inner subassembly has a molybdenum heater cup to which a tungsten-rhenium alloy cap is laser seam-welded. The outer subassembly has a tantalum support cylinder within which the inner subassembly is supported by means of a three-point suspension in the form of tabs that are lanced from the tantalum cylinder and spot-welded to the heater cup. The heater has a coiled-coil design wherein the coils are coated with Al.sub.3 O.sub.3 and small particle tungsten powder to increase the coil's thermal emissivity. This thermally-efficient structure permits the achievement of high current density (greater than 3 Amperes per square centimeter) with heater power that is less than 1.3 Watts.

Abstract: A four-piece, easily manufactured dispenser cathode capable of current densities up to and exceeding 10 Amperes per square centimeter is particularly adapted for CRT applications because of its surprisingly low cost. A refractory material reservoir contains a pellet of tungsten and barium calcium aluminate and is sealed by a pellet of porous tungsten or tungsten mixture. The reservoir/pellet assembly is contained in a support cylinder to which the porous tungsten pellet may be welded. The inventive process includes the steps to prepare the pellets and assemble the four elements of the cathode.

Abstract: An emitter-dispenser housing for a controlled porosity dispenser cathode manufactured of a single material as a unitary piece by a chemical vapor deposition process in which a configured mandrel is coated with a layer of material such as tungsten, for example, so that when the mandrel is removed from the coating of material a hollow housing is formed having a side wall and an end wall which define a reservoir. In addition, intersecting strips of this same material as the coating, which had been placed in the mandrel, extend transversely across the reservoir with the edges thereof atomically bonded to the coating during the chemical vapor deposition to form a unitary piece. Thereafter an array of apertures is formed in the end wall of the housing by laser drilling to create an emitter-dispenser.

Abstract: A dispenser cathode is fabricated by covering a reservoir of electron emitting material with a perforated metal foil having an appropriate pattern of pore-sized apertures thereon for providing uniform electron emission from the cathode surface. The electron emitting material is in the form of a pellet of barium oxide impregnated with a wax or resinous material to minimize chemical reduction of the barium oxide in air. The impregnated barium oxide pellet is sandwiched between the apertured foil and a support structure to which the foil is welded. During tube bake-out or subsequently during cathode activation, the wax or resinous material evaporates and barium oxide migrates through the apertures to cover the surface of the foil in a uniform manner. The desired pattern of apertures in the foil is achieved by photolithography, or by forming the foil (e.g., by chemical vapor deposition, sputter deposition, evaporation, or sintering) on a substrate containing an array of protruding posts.

Abstract: Secondary electrons emitted from an electron-collecting electrode of a vacuum tube degrade the performance. Emission of high-speed secondaries is reduced by coating the electron-collecting surface with a material of low atomic number. Emission of low-speed secondaries is a less predictable function of the surface material and structure. The invention comprises a coating of aluminum boride or similar substance, which has low secondary emission and is also easy to outgas.

Abstract: The performance of microwave tubes at very high frequencies is limited by the ability of their thermionic cathodes to provide high emission current density in combination with long life and low evaporation of active material. An improved tube uses a cathode comprising a porous metal matrix consisting of a compacted mixture of tungsten and iridium particles, impregnated with a molten barium aluminate. Other alkaline earth oxides may be used as additives. The impregnated cathode outgasses easily and has a long life because it is not dependent on thin surface films. Thermionic emission is improved compared to a tungsten matrix, and barium evporation is reduced. The combination of power and frequency obtainable from the microwave tube is thereby significantly increased.

Abstract: A traveling wave tube adapted for periodic magnetic focusing of the electron beam has a thin-walled, non-magnetic cylinder around the slow-wave circuit portion, forming part of the vacuum envelope. A stack of metal rings surrounding the cylinder has alternating non-magnetic rings and magnetic rings, the latter forming the periodic magnet pole pieces. The rings and the thin cylinder are all brazed together to provide a strong structure. Since the cylinder does not have to be self-supporting, it is made thin enough to allow close spacing between the pole pieces and beam, providing strong magnetic field and good focusing. The brazed joints between rings are not vacuum joints, so the probability of leaks is greatly reduced.