Abstract: A monolithic graphite heater for heating a thermionic electron cathode includes first and second electrically conductive arms, each one of the first and second electrically conductive arms having an electrode mount at a proximal end, a thermal apex at a distal end, and a transitional region between the electrode mount and the thermal apex; a cathode mount electrically and mechanically coupling each thermal apex to form a maximum Joule-heating region at or adjacent the cathode mount and decreasing Joule-heating along each transitional region; and a press-fit aperture formed in the cathode mount, the press-fit aperture sized to receive at least a portion of the thermionic electron cathode for facilitating thermionic emission produced therefrom in response to operative heat power generation provided by the maximum Joule-heating region.

Abstract: A monolithic graphite heater for heating a thermionic electron cathode includes first and second electrically conductive arms, each one of the first and second electrically conductive arms having an electrode mount at a proximal end, a thermal apex at a distal end, and a transitional region between the electrode mount and the thermal apex; a cathode mount electrically and mechanically coupling each thermal apex to form a maximum Joule-heating region at or adjacent the cathode mount and decreasing Joule heating along each transitional region; and a press-fit aperture formed in the cathode mount, the press-fit aperture sized to receive at least a portion of the thermionic electron cathode for facilitating thermionic emission produced therefrom in response to operative heat power generation provided by the maximum Joule-heating region.

Abstract: An electron emitter that consists of: a low work function material including Lanthanum hexaboride or Iridium Cerium that acts as an emitter, a cylinder base made of high work function material that has a cone shape where the low work function material is embedded in the high work function material but is exposed at end of the cone and the combined structure is heated and biased to a negative voltage relative to an anode, an anode electrode that has positive bias relative to the emitter, and a wehnelt electrode with an aperture where the cylindrical base protrudes through the wehnelt aperture so the end of the cone containing the emissive area is placed between the wehnelt and the anode.

Abstract: An electron source emitter is made from transition metal carbide materials, including hafnium carbide (HfC), zirconium carbide (ZrC), titanium carbide (TiC), vanadium carbide (VC), niobium carbide (NbC), and tantalum carbide (TaC), which are of high refractory nature. Preferential evaporating and subsequent development of different crystallographic planes of the transition metal carbide emitter having initially at its apex a small radius (50 nm-300 nm) develop over time an on-axis, sharp end-form or tip that is uniformly accentuated circumferentially to an extreme angular form and persists over time. An emitter manufactured to the (110) crystallographic plane and operating at high electron beam current and high temperature for about 20 hours to 40 hours results in the (110) plane, while initially not a high emission crystallographic orientation, developing into a very high field emission orientation because of the geometrical change.

Abstract: An electron source is made from mixed-metal carbide materials of high refractory nature. Producing field-enhanced thermionic emission, i.e., thermal-field or extended Schottky emission, from these materials entails the use of a certain low work function crystallographic direction, such as, for example, (100), (210), and (310). These materials do not naturally facet because of their refractory nature. The disclosed electron source made from transition metal carbide material is especially useful when installed in a scanning electron microscope (SEM) performing advanced imaging applications that require a high brightness, high beam current source.

Abstract: An electron source is made from mixed-metal carbide materials of high refractory nature. Producing field-enhanced thermionic emission, i.e., thermal-field or extended Schottky emission, from these materials entails the use of a certain low work function crystallographic direction, such as, for example, (100), (210), and (310). These materials do not naturally facet because of their refractory nature. The disclosed electron source made from transition metal carbide material is especially useful when installed in a scanning electron microscope (SEM) performing advanced imaging applications that require a high brightness, high beam current source.

Abstract: A thermionic emission assembly includes a Wehnelt cap that has a cap beam aperture and a cavity within which a cathode is supported. Electrical energy applied to the cathode causes it to reach a sufficiently high temperature to emit a beam of electrons that propagate through the cap beam aperture. An anode having an anode beam aperture is positioned in spatial alignment with the cap beam aperture to receive the electrons. The anode accelerates the electrons and directs them through the anode beam aperture for incidence on a target specimen. A ceramic base forms a combined interface that electrically and thermally separates the Wehnelt cap and the anode. The thermal isolation of the Wehnelt cap from the anode allows the Wehnelt cap to increase in heat to rapidly reach a stable temperature as the cathode emits the beam of electrons.

Abstract: A thermionic emission assembly includes a Wehnelt cap that has a cap beam aperture and a cavity within which a cathode is supported. Electrical energy applied to the cathode causes it to reach a sufficiently high temperature to emit a beam of electrons that propagate through the cap beam aperture. An anode having an anode beam aperture is positioned in spatial alignment with the cap beam aperture to receive the electrons. The anode accelerates the electrons and directs them through the anode beam aperture for incidence on a target specimen. A ceramic base forms a combined interface that electrically and thermally separates the Wehnelt cap and the anode. The thermal isolation of the Wehnelt cap from the anode allows the Wehnelt cap to increase in heat to rapidly reach a stable temperature as the cathode emits the beam of electrons.

Abstract: A thermionic emission assembly includes a Wehnelt cap that has a cap beam aperture and a cavity within which a cathode is supported. Electrical energy applied to the cathode causes it to reach a sufficiently high temperature to emit a beam of electrons that propagate through the cap beam aperture. An anode having an anode beam aperture is positioned in spatial alignment with the cap beam aperture to receive the electrons. The anode accelerates the electrons and directs them through the anode beam aperture for incidence on a target specimen. A ceramic base forms a combined interface that electrically and thermally separates the Wehnelt cap and the anode. The interface thermally isolates the Wehnelt cap from the anode to allow the cathode to rapidly reach the sufficiently high temperature to emit the beam of electrons.

Abstract: A radiant gas burner is provided having a casing adapted for connection with an air-gas mixing and supply system including a flux dissector and a mixer. The burner further includes a metallic mesh emitter inside the casing having lower and upper meshes. The lower mesh and the upper mesh each have porous openings. Each of the lower and upper meshes having a radius of curvature wherein the lower mesh is spaced apart from the upper mesh.

Abstract: Radiographic images may be produced electronically for diagnostic purposes during radiation therapy by utilizing a portable cart-based electronic portal imaging system wherein a photo-stimulable phosphor screen is mounted on the cart by a manipulable stanchion/arm assembly enabling selective positioning movement of the screen horizontally, vertically, and angularly relative to the cart among various spacial orientations as necessary to subtend the radiation beam. A camera and a computer are mounted on the cart to photographically capture and digitize X-ray images produced by the screen and to remotely transmit such images for diagnostic purposes of confirming and, as necessary, adjusting patient positioning.