Abstract: An oil-free electron source including a vacuum chamber within which a vacuum is maintained. A rigid insulated receptacle and an anode extend into the vacuum chamber and are mounted to opposite ends of the housing. A cathode-focus electrode assembly is mounted to an outer end of the receptacle and is suspended within the vacuum chamber by the receptacle. A high voltage connector is inserted into the receptacle and conveys voltage in an oil-free environment. The cathode and anode surfaces face each other and are aligned with respect to each other along an electron beam axis. The electron source may be provided within an electron beam scanner including a patient table, an x-ray source and detector obtaining x-ray scans of a patient, and a focus member directing an electron beam onto the x-ray source.

Abstract: An electron source includes a vacuum chamber within which a vacuum is maintained by a vacuum pump. An insulated receptacle is mounted within the vacuum chamber and has a receptacle mounting flange. The receptacle mounting flange is used to establish a coordinate system having an electron beam axis and a lateral plane, wherein the lateral plane is transverse to the electron beam axis. An adapter is mounted to the receptacle and is adjustable in five degrees of freedom with respect to the coordinate system. A cathode and focus electrode are adjustable in at least four degrees of freedom and are pre-aligned with respect to one another prior to being installed on the adapter. An anode is mounted in the vacuum chamber and is aligned at a predetermined distance from the cathode with respect to the coordinate system.

Abstract: An electron source includes a vacuum chamber within which a vacuum is maintained by a vacuum pump. An insulated receptacle is mounted within the vacuum chamber and has a receptacle mounting flange. The receptacle mounting flange is used to establish a coordinate system having an electron beam axis and a lateral plane, wherein the lateral plane is transverse to the electron beam axis. An adapter is mounted to the receptacle and is adjustable in five degrees of freedom with respect to the coordinate system. A cathode and focus electrode are adjustable in at least four degrees of freedom and are pre-aligned with respect to one another prior to being installed on the adapter. An anode is mounted in the vacuum chamber and is aligned at a predetermined distance from the cathode with respect to the coordinate system.

Abstract: An oil-free electron source including a vacuum chamber within which a vacuum is maintained. A rigid insulated receptacle and an anode extend into the vacuum chamber and are mounted to opposite ends of the housing. A cathode-focus electrode assembly is mounted to an outer end of the receptacle and is suspended within the vacuum chamber by the receptacle. A high voltage connector is inserted into the receptacle and conveys voltage in an oil-free environment. The cathode and anode surfaces face each other and are aligned with respect to each other along an electron beam axis. The electron source may be provided within an electron beam scanner including a patient table, an x-ray source and detector obtaining x-ray scans of a patient, and a focus member directing an electron beam onto the x-ray source.

Abstract: A method and apparatus are disclosed for reducing variation in a spot size of an electron beam at a target due to multipole aberrations in an electron beam tomography (EBT) scanner. A magnitude of a DC voltage applied to a positive ion electrode (PIE) within the EBT scanner is adjusted and an orientation of a non-circular aperture of the PIE is aligned with respect to the electron beam. A profile of the spot size is monitored while adjusting the magnitude of the DC voltage and while aligning the orientation of the non-circular aperture of the PIE until the variation in the spot size is sufficiently reduced.

Abstract: A method and apparatus are disclosed for reducing variation in a spot size of an electron beam at a target due to multipole aberrations in an electron beam tomography (EBT) scanner. A magnitude of a DC voltage applied to a positive ion electrode (PIE) within the EBT scanner is adjusted and an orientation of a non-circular aperture of the PIE is aligned with respect to the electron beam. A profile of the spot size is monitored while adjusting the magnitude of the DC voltage and while aligning the orientation of the non-circular aperture of the PIE until the variation in the spot size is sufficiently reduced.

Abstract: In a scanning electron beam CT system, a positive ion clearing electrode system is disposed within the CT system solenoid coil, and is operated from a single power source. Mounted coaxially about the electron beam, preferably the electrode system includes three sections, each having two electrode elements, one element being coupled to about −800 V to about −2 kV and the other element being grounded. Within the electrode system, the ratio between element diameter and electron beam diameter is substantially constant. Preferably elements are helically twisted about the beam axis. The electrode configuration cancels net quadrupole (focusing) and octopole (aberration-producing) fields. In the presence of electric discharge, essentially zero electron beam displacement and deflections occurs, and changes in focusing strength remain zero.

Abstract: In a scanning electron beam CT system, spherical aberration of the electron self-forces produces a deleterious halo around the final electron beam spot, causing loss of definition in the image rendered by the system. The spherical aberration is caused by non-uniform electron beam current density, and by non-uniform distribution of positive ions in the transition region of the beam-optical systems. The non-uniform electron beam current density depends upon the axial position of the electron gun cathode, while the transition region ion distribution depends upon the potential coupled to the washer-shaped positive ion electrode ("PIE") used to segregate the upstream and downstream portions of the electron beam. In the present invention, the beam spot halo is minimized (if not eliminated), and image definition is maximized by selecting the electron gun cathode axial position and the PIE potential such that their contributions to spherical aberrations at the final beam spot cancel.