Abstract: A field emission array electron source (12) is used to generate an electron beam in a x-ray generating device (10). The field emission array operates at room temperature and has a life expectancy in excess of 12,000 hours and provides a robust, efficient emitter for generating an electron beam in a x-ray generating device cathode (10).

Abstract: A dual filament x-ray tube assembly (16) includes an evacuated envelope (52) having an anode (54) disposed at a first end of the evacuated envelope (52) and a cathode assembly (62) disposed at a second end of the evacuated envelope (52). The cathode assembly includes a variable-length filament assembly (72, 74; 100) which emits electron beams for impingement on the anode (54) at focal spots having varying lengths. The cathode assembly (62) further includes a cathode cup (64, 66, 68; 110, 112) which is subdivided into a plurality of electrically insulated deflection electrodes (64, 66, 68; 110, 112). A filament select circuit (80) selectively and individually heats a portion of the variable-length filament assembly (72, 74). Electron beams emitted from the filament assembly (72, 74) are electrostatically focused and controlled by applying potentials to different ones of the deflection electrodes (64, 66, 68; 110, 112).

Abstract: A photon generator includes an electron gun for emitting an electron beam, a laser for emitting a laser beam, and an interaction ring wherein the laser beam repetitively collides with the electron beam for emitting a high energy photon beam therefrom in the exemplary form of x-rays. The interaction ring is a closed loop, sized and configured for circulating the electron beam with a period substantially equal to the period of the laser beam pulses for effecting repetitive collisions.

Abstract: The invention provides a scheme in accordance with which a linear accelerator may be operated in two or more resonance (or standing wave) modes to produce charged particle beams over a wide range of output energies so that diagnostic imaging and therapeutic treatment may be performed on a patient using the same device. In this way, the patient may be diagnosed and treated, and the results of the treatment may be verified and documented, without moving the patient. This feature reduces alignment problems that otherwise might arise from movement of the patient between diagnostic and therapeutic exposure machines. In addition, this feature reduces the overall treatment time, thereby reducing patient discomfort.

Abstract: An x-ray tube having a cathode and an anode disposed within an evacuated housing is disclosed. The cathode is spaced apart from a target surface formed on the anode and the anode is placed at a positive voltage relative to the cathode so that electrons emitted from the cathode accelerate towards and strike the target surface at a focal spot. The resulting collision produces x-rays. The cathode assembly includes a cathode support base, upon which is mounted a filament for emitting electrons. A first focusing mechanism focuses the emitted electrons into an electron beam. In illustrated embodiments, a pair of deflector plates are also supported upon the cathode support base. Voltage potentials are applied to the deflector plates so as to create a deflection region which alters the trajectory of the electron beam and thereby reposition the focal spot on the anode target.

Abstract: A mini-blind actuator has a motor and a housing that holds the motor and a dc battery. The rotor of the motor is coupled to the baton of the mini-blind for rotating the baton and thereby opening or closing the slats of the mini-blind. Alternatively, the rotor is coupled to the tilt rod of the blind to rotate the tilt rod and thereby open or close the slats of the mini-blind. A control signal generator generates a control signal for completing the electrical circuit between the battery and the motor. The control signal can be generated in response to a predetermined amount of daylight or in response to a user-generated remote command signal. The actuator can be used to rotate the slats of horizontal or vertical blinds, or the sections of a pleated shade. Or, the actuator can be used to rotate the hollow rotatable tube of a roll-up shade.

Abstract: In order to produce X-ray radiographic images consistently with high quality regardless of the magnitude of body thickness or motion of an examined site, a radiographic irradiation time threshold readout section 4 reads a radiographic irradiation time threshold Th corresponding to an examined site input by an operator out of a radiographic irradiation time threshold table 3, and an irradiation condition determining section 5 and radiographic irradiation time comparing section 6 select a larger radiographic focus size as the radiographic focus size for an X-ray tube 1 if Th<radiographic irradiation time Ts, and select a smaller radiographic focus size if Th radiographic irradiation time Ts.

Abstract: A hood electrode attached to a tip portion of a target is provided with an electron passage port widening on the side opposite from an x-ray emitting window, so that electrons emitted from an electron gun are made incident on the front end face of a target at a position on the x-ray emission side, whereby the distance between the x-ray generating position and the x-ray emitting window can be shortened.

Abstract: In an X-ray tube having an anode supported for rotation and an annular target track mounted upon the anode, a cathode spaced apart from the anode projects a beam of electrons onto the target track within a focal spot. The cathode is designed to normalize the impact temperature across the focal spot, as a function of length. In accordance therewith, the cathode comprises a filament and a cathode cup, wherein the filament is disposed to project the electron beam onto the target track to generate X-rays, when a high voltage potential difference is established between the filament and the anode. The filament and the cathode cup are respectively configured to selectively form the electron beam so that the beam provides an electron distribution within the focal point which maintains each point within the focal spot at substantially the same temperature.

Abstract: An x-ray tube providing excellent assembleability and handleability. An electrically conductive metallized layer 11 is provided on the surface of a stem 3. Therefore, when the x-ray tube 1 is being produced, thermally fusing nature of brazing material A provided between the stem 3 and the lower edge portion 8a of the focussing electrode 8 can be improved by the metallized layer 11. Further, the metallized layer 11 extends from the lower edge portion 8a of the focussing electrode 8 to the low voltage cathode pin 5a. Therefore, electric continuity between the focussing electrode 8 and the low voltage cathode pin 5a is achieved on the surface 3a of the stem 3. There is no need for separate wiring operations after the x-ray tube 1 is assembled. Connection between the focussing electrode 8 and the cathode pin 5a can be completed simultaneously with completion of the brazing connection.

Abstract: The invention relates to an X-ray tube whose cathode arrangement includes a flat electron emitter that is provided with openings. An electrode is arranged on the side of the electron emitter that is remote from the anode of the X-ray tube; this electrode carries a negative potential relative to the electron emitter, which negative potential straightens the electron paths in front of the emitter. These steps result in a favorable ratio of the dimensions of the electron emitter to the dimensions of the focal spot formed on the anode by the emitted electrons.

Abstract: An X-ray tube comprising an anode having a target surface radiating X-rays from a position of an X-ray focal spot by impingement of an electron beam, a focusing electrode and cathodes. The focusing electrode has a bottom portion positioned facing the target surface of the anode and most remote from the X-ray focal spot, at least one inclined wall surface obliquely ascending from the bottom portion in the direction of the anode, and substantially rectangular focusing recesses formed at the inclined wall surface. Each of the cathodes emits electron beams, positioned respectively in the focusing recesses of the focusing electrode. The focusing recess has first and second corners which curve from at least one end wall facing the end of the cathode to two side walls along the direction of the longer side of the cathode, and the first corner located remote from the bottom portion is gentler than the second corner located adjacent to the bottom portion with reference to condition of curving.

Abstract: A system for generating tunable pulsed monochromatic X-rays comprises a tabletop terawatt laser delivering 10 Joules of energy in 10 ps at a wavelength of 1.1 microns. The light beam from the laser is counter-propagated against an electron beam produced by a linear accelerator. X-ray photons are generated by inverse Compton scattering that occurs as a consequence of the “collision” that occurs between the electron beam and IR photons generated by the laser. The system uses a novel pulse structure comprising, in a preferred embodiment, a single micropulse. The LINAC is configured to generate an electron beam having 1 nanocoulomb of charge in a microbunch having a pulse length of about 5 picoseconds or less (or an electron beam brightness of 1012 A/m2−radian2@ 500 A).

Abstract: X-ray tube with flying focus has a magnet system for deflecting and focusing the electron beam, whereby the magnet system including a carrier that is constructed as an iron yoke and that has four pole projections that are arranged around the axis of the electron beam offset from one another by 90°, on which two pairs of coils (z-coils and &phgr;-coils) are arranged so as to be offset from one another 90°. The individual coils of each pair supplied with a common high-frequency alternating current that deflects the electron beam in the &phgr;-and z-directions, respectively, in a pulsed manner.

Abstract: An X-ray generator comprises an evacuated and sealed X-ray tube, an electron gun, an X-ray target, an internal electron mask, and an X-ray window consisting of a thin tube of material with low X-ray absorption and high mechanical strength, for example beryllium. The window connects the tube to the target assembly containing the X-ray target. The generator preferably also includes a system for focusing and steering the electron beam onto the target, a cooling system to cool the target material, kinematic mounts to allow precise and repeatable mounting of X-ray devices for focusing the X-ray beam, and X-ray focusing devices of varying configurations and methods. The X-ray generator of the invention produces an X-ray source having a focal spot or line of very small dimensions and is capable of producing a high intensity X-ray beam at a relatively small point of application using a low operating power.

Abstract: An X-ray tube including an electron source and a magnetic guide. The X-ray tube includes at least one electron source, at least one microtip, and an extraction grid, one zone of which emits electrons. Further provided are at least one anode, one zone of which emits X-rays under the impact of the electrons, and a magnetic guiding device for the electrons, capable of creating a magnetic field which is homogeneous at least between the zones. Such an X-ray tube may find application to X-ray absorption analysis or X-ray fluorescence analysis.

Abstract: Air cooled x-ray generating apparatus is provided with a unitary vacuum enclosure having a rotating anode target and a cathode assembly for generating x-rays. The cathode assembly may be placed within the vacuum enclosure through an opening in the top wall thereof, and comprises a disk which completely covers this opening. The unitary vacuum enclosure and the disk form a radiation shield. A plurality of fins are disposed on the exterior side wall of the vacuum enclosure, and a shroud is attached to the fins to provide additional protection of ambient against radiation. The cathode assembly may be placed through a side wall of the vacuum enclosure. The additional protection against excessive radiation in this design is provided by a shielding member placed in proximity to the anode target. The shielding member extends from the side wall of the enclosure and is substantially parallel to the top wall.

Abstract: A radio therapy system includes measuring an actual position of a micro-radiation source and radiation dose actually generated from the source, at predetermined times, during a therapeutic treatment. An accumulative radiation dose distribution is constantly generated in realtime, during the treatment, from the actually measured position and radiation dose and reference radiation dose distribution. An operator can monitor, in realtime, how the radiation dose distribution is developed, temporally, during the treatment. As a result, it is possible to irradiate a lesion with a requisite dose of radiation, minimize any un-required irradiation to a normal area around the lesion and achieve a therapeutic treatment with high precision.

Abstract: An X-ray tube 1 includes spacer 8 which is cylindrical so it does not block electrons 80 directed from a grid electrode 72 toward a focusing electrode 25, and which has one end 8b fixed to the grid electrode 72 and the other end 8c abutting against the focusing electrode 25. The distance between the grid electrode 72 and focusing electrode 25 is set to a predetermined distance by the spacer 8.

Abstract: A variable spot size x-ray tube comprises a cathode having an electron emitting surface providing an electron beam that travels essentially along the tube axis of symmetry to an anode. The anode, spaced from the cathode, includes a target, the front surface of which is disposed at an oblique angle with respect to the axis of symmetry. The potential of the anode is generally positive with respect to that of the cathode. The cathode is heated to a temperature at which electrons are emitted by the thermionic emission process. Current from the cathode can be controlled by varying the cathode temperature if the cathode is operated in the temperature limited region. The incident electron beam forms a spot on the target surface whereupon x-rays are produced in response to impingement of the electron beam on the target. The x-rays propagate outwardly from the target spot through a vacuum window to form a beam of x-radiation outside the x-ray tube.

Abstract: The radiology instrument contains a source emitting X-radiation, a radiological image receiver, a chassis arranged between the X-ray source and the image receiver in order to accommodate an object to be radiographed, and a positioning and guiding device which can be connected to the chassis and can intercept the X-radiation so as to position and guide probes intended to interact with the object. The positioning and guiding device has first means forming a retractable guide grid having holes whose respective axes converge towards the focal point of the source when the first means intercept the conical radiation, and a retractable positioning grid with holes.

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: The present invention, in one form, is a system for correcting thermal drift in an imaging system. More specifically, a correction algorithm determines an adjusted focal spot position based upon a first temperature focal spot position and a second temperature focal spot position. The adjusted focal spot position is utilized in the reconstruction process to correct for focal spot movement resulting from thermal drift.

Abstract: In a method and x-ray system for controlling the electron current in an x-ray tube emitted from a continuously heated electron emitter with an allocated focussing electrode to an anode, the potential of the focussing electrode is pulsed between a conducting-state voltage, selected dependent on the desired size of the focal spot and/or the tube voltage of the electron beam on the anode, and a blocking voltage interrupting the electron current to the anode, the pulsewidth being modulated to control the electron current.

Abstract: Tuning, integrating, and operating an electron beam CT scanning system is simplified by using the fringe field from dipole magnets arranged as a chicane to focus the electron beam, thus replacing conventional quadrupole and solenoid coils. Preferably four "chicane" dipole magnets are series-coupled with the windings in the downstream deflection magnet, such that the chicane magnet X and Y coils are energized 90.degree. out of phase with the deflection magnet coils. The alternating current polarity in the chicane magnets creates an "S"-shaped electron beam trajectory that adequately uniformly focuses over the full cross-section of the electron beam. Winding the coils with a cosine distribution permits rotating the magnetic fields to change the azimuthal and deflecting planes of the electron beam, without disturbing the deflection angle and focusing properties.

Abstract: An X-ray tube uses a magnetic field to steer electrons. The magnetic field urges electrons toward the anode, increasing the proportion of electrons emitted from the cathode that reach desired portions of the anode and consequently contribute to X-ray production. The magnetic field also urges electrons reflected from the anode back to the anode, further increasing the efficiency of the tube.

Abstract: An x-ray tube has a cathode and an anode which are arranged in a vacuum housing, with an electromagnet for deflecting the electron beam traveling from the cathode to the anode. This electromagnet is formed by a C-shaped yoke with two legs that are connected to each other by a base section surrounded by a winding. Respective pole shoes with opposing pole faces are disposed at the ends of the legs. The electron beam passes between the two pole shoes as it propagates from the cathode to the anode. Each pole face has a width which does not exceed the width of its pole shoe.

Abstract: In an X-ray device which includes an X-ray tube (12) provided with means (15, 22, 23) for influencing the electron flow through the X-ray tube (12), a control voltage for the means for influencing the electron flow is customarily generated by means of a complex circuit which, because of its size, is not suitable to be accommodated within the protective tube housing. This has the drawback that the control voltage for the X-ray tube, usually of high voltage potential, must be supplied additionally to the high-voltage supply. Therefore, it is desirable to realize a simple generation means the control voltage which is suitable for accommodation in the protective tube housing. To this end, the invention proposes a piezoelectric transformer (21, 24, 25) for generating the control voltage for the X-ray tube. The invention also relates to a piezoelectric transformer which is particularly suitable for generating such a control voltage.

Abstract: An x-ray tube has a cathode and an anode arranged in a vacuum housing, wherein an electron beam emanating from the cathode is incident at a focal spot on the anode. An electromagnet is provided for deflecting the electron beam, this electromagnet having a U-shaped yoke with two legs connected by a base section with a winding surrounding the base section. The electron beam passes between the two legs. The yoke is formed by successively layered laminations disposed in respective planes disposed substantially perpendicularly to the propagation direction of the electron beam.

Abstract: An X-ray generator for powering an X-ray tube, has at least two electron sources for forming focal spots of different sizes at the same area of the anode. The resolution can be adapted to relevant requirements by associating each electron source with a respective control unit which produces an electron flow between the associated electron source and the anode, which flow is dependent on a control signal at a control input of the control unit, the two control units being activatable during an X-ray exposure and each control signal being adjustable, and hence also the ratio of the mAs products supplied by the electron sources.

Abstract: An X-ray tube with a cathode and an anode arranged in a vacuum housing has an electromagnet for deflecting the electron beam emanating from the cathode and proceeding to the anode, the electromagnet having a yoke with two legs connected to one another by a base section, with a winding surrounding the base section. The base section with the winding is located outside the vacuum housing. The legs of the yoke of the electromagnet extend into the vacuum housing so that the electron beam proceeds between the two legs.

Abstract: An X-ray tube has a cathode and an anode that are arranged in a vacuum housing. For deflection of the electron beam propagating from the cathode to the anode, two electromagnets are provided, of which each having a U-shaped yoke with two arms connected with one another by a base segment, and comprises a winding surrounding the base segment. The respective end faces of the arms of the two yokes are arranged opposite one another so as to maintain an air gap. The magnetic poles positioned opposite one another have the same polarity. The electron beam proceeds through the opening limited by the two yokes.

Abstract: A transmission type X-ray tube is provided with a ceramic stem fitted with cathode pins; an output window, the lower surface of which is deposited with a target metal; a ceramic bulb provided between the ceramic stem and the output window; and a focusing electrode provided along the inner surface of the ceramic bulb and which lower end is interposed between the upper surface of the ceramic stem portion and the lower end of the ceramic bulb. With this configuration, not only can the size of the X-ray tube be reduced, but mounting of the focusing electrode can also be made easier, thereby simplifying assembly operations.

Abstract: A high-intensity, inexpensive and collimated x-ray source for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications.

Abstract: An X-ray tube assembly having a cathode, an anode, and an electrode surrounded by a vacuum-enclosing frame. Electrons from the cathode strike a target surface on the anode. Some electrons produce X-rays which exit an X-ray transparent window portion of the frame. Other electrons are backscattered and go on to strike and heat the frame including the window region. The non-electron-emifting electrode typically has a negative electrical potential and is positioned to deflect the backscattered electrons away from the window region which reduces heating thereto and hence minimizes tube failure.

Abstract: An x-ray tube has an anode and a cathode arrangement mounted at a distance from the anode and having an electron emitter, the cathode arrangement containing structure for focusing the electron beam that emanates from the electron emitter during operation of the x-ray tube and which is incident on the anode in a focal spot, the focus of the electron beam being located between the electron emitter and the focal spot.

Abstract: An X-ray tube has a cathode and an anode arranged in a vacuum housing, the electron beam emanating from the cathode proceeding through a hollow cylindrical housing part of the vacuum housing to the anode. An electromagnet is provided for the deflection of the electron beam. The electromagnet has a U-shaped yoke with two legs having first ends connected to one another by a base section and having a winding surrounding the base section. The legs straddle the housing part and the electromagnet is disposed so that the electron beam is spaced a distance from the second ends of the legs so that from the second ends of the legs so that the electron beam is situated only in the stray field of the electromagnet, rather than in the region of maximum field strength.

Abstract: A method and apparatus for superimposing a plurality of electron beams at a desired location after X-ray tube manufacturing processes are generally complete. The method is embodied in providing mechanical and electrical means which are internal to the X-ray tube which provide means for adjustment of a focal point of a plurality of electron beams being emitted from a cathode assembly to thereby provide precise control of where the plurality of electron beams achieve superimposition on a target anode.

Abstract: A high-intensity, inexpensive and collimated x-ray source for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications.

Abstract: An x-ray tube with vario-focus has an evacuated housing in which are arranged, rigidly connected thereto, an electron-emitting cathode and an anode dish which is struck by the electron beam, accelerated with an electrical field. An electromagnetic system for deflecting and focusing the electron beam is provided, and has a number of current-permeated coil elements. A lateral x-ray beam exit window is provided in the housing for the x-rays, which emerge at substantially a right angle relative to the longitudinal middle axis. The x-rays are picked up by an image receiver following a subject table. At least the anode dish is tiltable relative to the connecting axis to the image receiver, and the electromagnetic system at least partially surrounds a cathode-side neck section of the housing, and generates a quadrupole field for modifying the electron beam cross-section, corresponding to the tilt angle.

Abstract: An x-ray tube has an evacuated housing in which an electron-emitting cathode is rigidly mounted and a rotating anode having an anode dish rotatable by a drive arrangement, which is struck by the electron beam, accelerated with an electrical field, for producing x-rays. An electromagnetic system for the deflection and focusing of the electron beam has a number of current-permeated coil elements. The cathode generates a rotationally-symmetrical circular beam, and the rotational axis of the anode dish is offset from and parallel to the axis of the electron beam by the average radius of the anode dish edge. The electromagnetic system generates a dipole-free quadrupole field that deforms the electron beam cross-section.

Abstract: An X-ray source is disclosed having an enclosure, typically made of metal or glass. A cathode assembly is contained within the enclosure and the cathode assembly has two through openings along a predefined axis. An anode is also contained within the enclosure at a position spaced from the cathode assembly. The anode, furthermore, has a face normal to the predefined axis so that a portion of the X-rays emitted from the anode pass through the cathode assembly opening and exteriorly of the enclosure.

Abstract: An X-ray tube has an anode and a photocathode inside a vacuum envelope and an electron multiplier is disposed between them. Such an electron multiplier may be a plurality of sequentially disposed dynodes or a microchannel plate. Because of the secondary electron emission from such an electron multiplier, a higher-power radiation is obtained without requiring a high optical power level to generate photoelectrons. The vacuum envelope may be of a rotary type with the anode and photocathode having annular regions.

Abstract: A cathode system for an x-ray tube has an electron emitter and a further electrode arranged between electron emitter and the x-ray tube anode. This further electrode can be connected to a potential deviating from the potential of the electron emitter with a switching stage having a pulse-pause (on-off) ratio set to produce the desired tube current.

Abstract: An x-ray tube has an anode and a cathode arrangement mounted at a distance from the anode and having an electron emitter, the cathode arrangement containing structure for focusing the electron beam that emanates from the electron emitter during operation of the x-ray tube and which is incident on the anode in a focal spot, the focus of the electron beam being located between the electron emitter and the focal spot.

Abstract: An x-ray head according to the invention includes an evacuated chamber in which a cathode and an anode are disposed and electrical connections from the anode and cathode extending through the wall of the evacuated chamber. The cathode may include a gated array of field emission elements, an array of solid state miniature thermionic cathodes, or ferroelectric cathodes. The anode is a metal producing x-ray radiation in response to the impact of electrons produced by the cathode. The anode may be a foil, a thin film of metal deposited on the inside surface of a wall of the evacuated chamber, or a self-supporting body of a metal that produces x-rays in response to electron impacts. The wiring may include conventional pins penetrating through and sealed to the wall of the chamber for connection to a flexible cable.

Abstract: An x-ray tube has an anode and an electron emitter from which an electron beam emanates, the electron beam impinging the incident surface of the anode in a focal spot from which a useful x-ray beam emanates. At least in the region of its electron-emitting surface, the electron emitter is formed of an electron-emitting material that has a lower electron affinity than tungsten (a low-temperature emitter). Further, an apertured diaphragm at anode potential is arranged between the electron emitter and the anode and through which the electron beam passes. As electron-emitting material, the electron emitter contains lanthanum hexaboride (LaB.sub.6) or an alloy of the systems iridium/cerium (Ir/Ce) or iridium/lanthanum (Ir/La) systems.

Abstract: In an apparatus and a method for generating an x-ray beam circulating through a polar angle .phi. of 2.pi. that enables fast computed-tomographic scans is to be generated, an electron beam is generated with a predetermined energy and is injected into a beam guide that guides the electron beam on a spiral path in a plane by means of an axial magnetic field. At a location selectable in the .phi.-direction, the electron beam is deflected perpendicularly to the plane and onto an essentially annular anode arrangement, so that, proceeding from the point of incidence of the electron beam, x-rays directed onto the center of the anode arrangement are generated. For a scan, the selectable location at which the electron beam is deflected out of the plane is advanced along the spiral path, so that the point of incidence of the electron beam onto the anode arrangement advances correspondingly.

Abstract: In an x-ray beam computed tomography apparatus having a ring anode scanned by an electron beam for producing an x-ray beam which rotates around an examination region, measurement of the intensity distribution in the electron beam is enabled at various locations of the ring anode during operation. For this purpose, the ring anode can have at a number of locations around its circumferential direction, insulated sub-anodes with an insulating interspace therebetween, to which a measuring arrangement for measuring the charge distribution, and thus the intensity distribution, in the electron beam is connected. The charge distribution is measured when the electron beam sweeps the interspace between two sub-anodes.

Abstract: X-ray tube electron beam focusing utilizing a cathode having a large cavity therein in which an electron cloud is generated and which is shielded from the primary electric field between the cathode and the anode. The electron cloud flows from the cavity through a small narrow passage and into the primary electric field. An opposed spaced apart pair of electrical grids each comprising an array of individual electrode segments have selected opposed segments electronegatively biased to change the cross-section of the passing electron stream therebetween. The altered cross-section of the electron stream determines the size of the focal spot of the electron beam impacting the target anode.