Abstract: An isosurfacial three-dimensional imaging system and method uses scanning electron microscopy for surface imaging of an assumed opaque object providing a series of tilt images for generating a sinogram of the object and a voxel data set for generating a three-dimensional image of the object having exterior surfaces some of which may be obscured so as to provide exterior three-dimensional surface imaging of objects including hidden surfaces normally obscured from stereographic view.

Abstract: An electron source for an X-ray scanner includes an emitter support block, an electron-emitting region formed on the support block and arranged to emit electrons, an electrical connector arranged to connect a source of electric current to the electron-emitting region, and heating structure arranged to heat the support block.

Abstract: In an X-ray generating device (2) a temperature of a focal spot (21) may be determined. Furthermore a load condition is determined, which may also take into account a planned operation procedure of the X-ray generating device (2). The focal spot of the X-ray generating device is then automatically resizable based at least in part on the load condition.

Abstract: When the same subject is to be imaged consecutively plural times, a radiation imaging device is controlled so as to change an imaging time interval between respective imagings according to a set imaging region of the subject. When a chest portion of a subject is to be imaged, a control section designates an image obtained at a second imaging as an image for diagnosis, image quality correction processing is not performed at a first imaging, and an imaging time interval is greatly reduced compared to when other regions are imaged, thereby reducing motion artifacts of an energy subtraction image. When regions other than a chest region are imaged, the control section designates an image obtained at a first imaging as an image for diagnosis, performs image quality correction processing at the first imaging, and an imaging time interval is increased compared to when the chest region is imaged.

Abstract: Multibeam field emission x-ray systems and related methods can include cathode elements, an anode assembly spaced from the plurality of cathode elements, and an extraction gate positioned between the plurality of cathode elements and the anode assembly. A potential difference can be applied between the extraction gate and at least one of the cathode elements to cause an emission of electrons from the respective cathode elements. Emission characteristics of the cathode elements can be measured, and the potential difference between the extraction gate and at least one of the cathode elements can be adjusted based on the emission characteristics measured.

Abstract: A method is provided of calculating the structure of an inhomogeneous sample in which an electron beam is used to cause excitation of x-rays from the sample under known conditions of beam energy and geometry with respect to the sample. Notably the beam current is unknown. Measured x-ray intensity data for the sample corresponding to one or more sets of beam conditions and beam currents are firstly obtained, together with comparative x-ray intensity data for samples having known structures. A beam current factor for each beam condition is estimated and effective x-ray intensity data for each of the sets of conditions are then calculated using the measured and comparative x-ray intensity data and the beam current factor. The structure of the sample is then calculated for each of the sets of conditions using the effective x-ray intensity data. Predicting x-ray intensity data are produced corresponding to the calculated structure and compared with the effective x-ray intensity data.

Abstract: A segmented thermionic emitter is provided. The segmented thermionic emitter has, among other features, a plurality of segments substantially spanning an entire length of the thermionic emitter and aligned substantially parallel with one another. In one embodiment, the segmented thermionic emitter may allow milli-amp modulation of an X-ray tube at voltages less than approximately 2 kV.

Abstract: An x-ray-based radiation imaging apparatus (200) for use in imaging an object (201) can comprise a source of x-rays (202) having an output radiation intensity control input and a radiation intensity controller (207) operably coupled thereto. This radiation intensity controller can have a control output (209, 210) that is operably coupled to the output radiation intensity control input and an object information input (209). So configured, the radiation intensity controller can dynamically adjust radiation intensity as output by the source of x-rays as a function of information regarding the object itself.

Abstract: According to one embodiment, a system for interrogating hidden contents of a container comprises a controller, a detector system, and a data system. The controller receives a selection of a source mode of source radiation to generate to interrogate contents of a container. The source mode selection comprises a neutron mode, a gamma ray mode, or a combined neutron-gamma ray mode. The controller instructs a cyclotron to generate the source radiation according to the source mode selection. The detector system detects radiation emitted from the contents in response to the source radiation. The data system analyzes the emitted radiation and describes the contents according to the analysis.

Abstract: A Betatron having a toroidal passageway disposed in a cyclical magnetic field with a main electron orbit circumnavigating the toroidal passageway. Within the toroidal passageway is a first electrode that is spaced apart from a second electrode. The combination of the first electrode and the second electrode define a central space having a first opening and a second opening. A cathode is disposed within the central space. This cathode has a first electron emitter aligned to inject electrons through the first opening and a second electron emitter aligned to inject electrons through the second opening. Electrons injected in a proper direction are accelerated in the main electron orbit. At a time of maximum electron acceleration, the electrons are deflected and impact a target that generates x-rays on impact.

Abstract: An X-ray photoelectron spectroscopy analysis system for analysing an insulating sample 20, and a method of XPS analysis. The system comprises an X-ray generating means 30 having an exit opening 32 and being arranged to generate primary X-rays 46,56 which pass out of the exit opening in a sample direction towards a sample surface 22 for irradiation thereof. It has been found that the X-ray generating means in use additionally generates unwanted electrons 258 which may pass out of the exit opening substantially in the sample direction and cause undesirable sample charging effects. The system further comprises an electron deflection field generating means 380,480,580 arranged to generate a deflection field upstream of the sample surface. The deflection field is configured to deflect the unwanted electrons away from the sample direction, such that the unwanted electrons are prevented from reaching the sample surface.

Abstract: A radiation inspection apparatus includes a radiation source, a measurement radiation detecting unit being a rectangle having a long side, and a reference radiation detecting unit that is disposed between the radiation source and an inspection target, the reference radiation detecting unit being disposed near a path of a radiation from the radiation source to the measurement radiation detecting unit not to interrupt the radiation from the radiation source to the measurement radiation detecting unit. An intensity of the radiation source are corrected by calculating a change value of the intensity and the intensity distribution from an output of the reference radiation detecting unit and by correcting the output of the measurement radiation detecting unit based on the change value.

Abstract: X-ray apparatus comprises a linear accelerator adapted to produce a beam of electrons at one of at least two selectable energies and being controlled to change the selected energy on a periodic basis, and a target to which the beam is directed thereby to produce a beam of x-radiation, the target being non-homogenous and being driven to move periodically in synchrony with the change of the selected energy. In this way, the target can move so that a different part is exposed to the electron beam when different pulses arrive. This enables the appropriate target material to be employed depending on the selected energy. The easiest form of periodic movement for the target is likely to be a rotational movement. The target can be immersed in a coolant fluid such as water. The linear accelerator can be of the type disclosed in WO2006/097697A1. The target preferably contains at least one exposed area of tungsten and/or at least one exposed area of carbon.

Abstract: An x-ray tube is described that includes components for increasing x-ray image clarity in the presence of a moving x-ray source by modifying focal spot characteristics, including focal spot size and focal spot position. In a first arrangement a static focal spot is moved in a direction contrary to the movement of the x-ray source so that an effective focal spot position is essentially fixed in space relative to one of the imaged object and/or detector during a tomosynthesis exposure. In a second arrangement, the size of the static focal spot is increased, and the resulting increase in tube current reduces the exposure time and concomitant blur effect. The methods may be used alone or in combination; for example an x-ray tube with a larger, moveable static focal spot will result in a system that fully utilizes the x-ray tube generator, provides a high quality image with reduced blur and, due to the decrease in exposure time, may scan the patient more quickly.

Abstract: An assembly for detection of at least one of radiation flux and contamination on an optical component includes a detector configured to receive at least one of the radiation flux and contamination, and when the assembly is in use, to generate a detector signal correlated to at least one of the radiation flux and contamination on the component. A meter is configured to measure the detector signal. The detector includes at least one wire.

Abstract: A compact, reliable scanning electron-beam x-ray source achieves reduced complexity and cost. In particular, the x-ray source includes an electron beam that is propagated parallel to an x-ray target and is swept across the target in response to a moving magnetic cross field. Rather than scanning the beam by deflecting it about a single point, the point of deflection is translated along the target length, dramatically reducing the volume of the device. The magnetic cross field is translated along the target length using either mechanical systems to move permanent magnets, or electrical systems to energize an array of electromagnets.

Abstract: A computer tomograph (1) that comprises at least a stationary electron source for generating an electron beam (13), a ring-shaped, stationary X-ray source with a largely ring-shaped target (14) enclosing a measuring field (7), media for coaxially guiding (22) the electron beam (13) in the X-ray source (5) along a circular path to the ring-shaped target (14), as well as media for deflecting (21) the electron beam (13) towards the target (14), in order to generate an X-ray cluster (8) that rotates concentrically around itself for irradiating the measuring field (7) from various directions. Furthermore, the computer tomograph (1) comprises a stationary detector (6) executed as a ring shape and consisting of numerous detector elements from which a computer calculates the measured values to create an image of the examined object in the measuring field (7). The ring-shaped target (14) has numerous discrete focal areas (20) that can be scanned discontinuously by a focal point of the electron beam (13?).

Abstract: A method of producing a cathode for use in an x-ray tube assembly is provided including machining an emission aperture into a cup emission surface portion of a cup structure. The cup structure is comprised of a cup base portion opposite the cup emissions surface portion. Electro-discharge machining is used to form an electro-discharge machining slot into the cup structure to provide access to the interior of the cup structure. Electro-discharge machining is used to form a transverse coil chamber within the interior by way of the electro-discharge machining slot such that the transverse coil chamber is formed between the cup base portion and the cup emissions surface portion while retaining an essentially contiguous emissions surface perimeter surrounding the emission aperture.

Abstract: A method includes performing an at least partially automated method to synchronize an x-ray source focal spot (FS) position to a FS deflection feedback signal.

Abstract: A method for controlling focal spot size changes of an x-ray source in an imaging system includes measuring focal spot sizes as a function of a plurality of x-ray source operating parameters, determining a calibration table or transfer function utilizing the measured focal spot sizes as a function of the plurality of x-ray tube operating parameters, and utilizing the calibration table or transfer function to control focal spot size variations during operation of the imaging system.

Abstract: A dose-modulated irradiating system includes an x-ray tube (20) with at least a filament (80) for generating electrons, a cathode (84) and an anode (92) for accelerating and collimating the generated electrons into an electron beam (94), and an electrostatic grid with grid electrodes (110, 112) for steering the electron beam (94) on the anode (92). The anode (92) generates an x-ray beam (96) responsive to the electron beam (94). Grid biasing is provided for applying a time-varying electrical bias to the grid electrodes (110, 112) that produces a first time-varying intensity modulation of the electron beam (94). A current of the filament (80) is modulated to produce a second time-varying intensity modulation of the electron beam (94). A controller (52) controls cooperatively combining the first and second time-varying intensity modulations to produce a combined time-varying intensity modulation.

Abstract: An optic device, system and method for imaging are described. The optic device includes a first solid phase layer having a first index of refraction with a first photon transmission property and a second solid phase layer having a second index of refraction with a second photon transmission property, the solid phase layers being situated between an output face and a non-flat input face. The first and second layers are conformal to each other. The imaging system includes a source of electrons and a target, with an array of the optic devices coupled thereto to form limited cone beams of X-ray radiation.

Abstract: Methods are provided through which X-ray tube power de-rating can be reduced during dynamic focal spot deflection. In one embodiment, a method comprising generating an electron beam, focusing the electron beam to a first position on an anode, defocusing the electron beam on the anode and refocusing the electron beam at a second position on the anode. In another embodiment, a method comprising generating an electron beam, focusing the electron beam to a first position on an anode, inhibiting the electron beam and refocusing the electron beam at a second position on the anode. In another embodiment, a method comprising generating an electron beam, focusing the electron beam to a first position on an anode, steering the electron beam away from a nominal focal spot radius on the anode and refocusing the electron beam at a second position on the anode.

Abstract: A method includes performing an at least partially automated method to synchronize an x-ray source focal spot (FS) position to a FS deflection feedback signal.

Abstract: An X-ray generator of this invention has an X-ray monitor that monitors a state of an X-ray emitted from a target. Hence the state of the X-ray can be monitored in real time to maintain the X-ray in a constant state. The X-ray monitor is positioned off the path on which an X-ray transmitted from a first exit window travels. Hence, when the X-ray is emitted from the first exit window to an object to be inspected, the X-ray monitor does not obstruct the approaching of the object to the first exit window. This makes it possible to acquire X-ray images of high magnification.

Abstract: A maximum tube voltage value setting module 240a, a warming-up module 240b, a limit tube voltage control module 240c, a limit tube current control module 240d and a focus grid electrode control module 240e of an operation program 240 which respectively correspond to different maximum tube voltage values are stored in storage sections 32a-e of an X-ray tube control apparatus 3. When the maximum tube voltage value of an X-ray tube 1 is changed, an extraction section 34 extracts each module of the operation program 240 which corresponds to the maximum tube voltage value after being changed from the storage sections 32a-e. A communications section 36 sends the operation program 240 comprised of each extracted module to an X-ray tube controller 2 and overwrites it in a memory section 24.

Abstract: A method for measuring focal spot shape of a radiation beam from a radiation source includes collimating the radiation beam using a collimator having a well-defined edge, measuring an intensity profile of the collimated radiation beam, determining a function of the measured intensity profile, and determining a metric of the of the focal spot using the determined function of the measured intensity profile.

Abstract: The non-destructive test of a structure (10) such as an aircraft fuselage is done by placing an X-ray source (16) on one side of the structure, and placing a digital camera (24) on the other side. The microcomputer (28) analyzes the image output by the digital camera in real time. If this image is unusable, at least one setting of the source (16) is modified immediately and a new acquisition is made without wasting any time. The adjustment can then be made manually or using a slaving system. The adjustment may relate to the wave length of the X-ray beam, the dose level or the pose time if the fault concerned is related to the gray level of the image. If a directional source is being used, the defect may also have an influence on the sharpness of the image and may be caused by an alignment problem.

Abstract: An X-ray generator 1 includes an X-ray tube 11 having a cathode portion 16, a grid electrode 15 and a target 22, a voltage controller 27 and 32 for controlling voltages to be applied to the cathode portion 16 and the grid electrode 15, and switches 33 and 34 for operating ON and OFF of the X-ray generator 1 and of X-ray emission. The voltage controller 27 and 32, based on an ON-signal for the X-ray generator 1 and an OFF-signal for the X-ray emission, applies a positive standby voltage Vf1 to the cathode portion 16 and applies a negative cutoff voltage Vc1 to the grid electrode 15.

Abstract: The invention relates to an X-ray tube which includes a device for at least substantially protecting an object to be examined against the incidence of undesirable X-rays (E) which can be produced notably by the decay of a residual or surplus charge present in a high-voltage circuit after an X-ray exposure. To this end there is provided at least one device (341, 342) for deflecting and/or defocusing the electron beam (E) produced by the residual and/or surplus charge in such a manner that at least it is not incident to a significant extent on a region (22) of an anode (2) wherefrom X-rays excited thereby are directed towards an object to be examined.

Abstract: A power source for the operation of a deflection coil for an electron beam of an x-ray tube has a voltage source and a bridge circuit that is connected with each end of the deflection coil, respectively via one power switch in series connection to opposite poles of the voltage source. A current tap taps a coil current signal proportional to the current through the deflection coil. An activation comparator and a deactivation comparator are connected with the current tap to which an activation current signal Imin and a deactivation current signal Imax are supplied. The power switches are connected with the activation comparator and deactivation comparator such that they are closed in the event that the coil current signal undershoots the activation current signal Imin and opened in the event that the coil current signal overshoots the deactivation current signal Imax.

Abstract: In a method and a device for setting the focal spot position of an X-ray tube the focal spot position is regulated as a controlled variable by a closed loop regulation circuit. A deflector deflects the electron beam of the X-ray tube depending on a deflection signal, a deflection closed loop regulator generates the deflection signal depending on a focal spot position signal. A measurement arrangement measures a focal spot position signal. The deflector, the deflection closed loop regulator and the measurement arrangement form a closed loop regulation circuit with the focal spot position as the controlled variable and with the deflection signal as the control parameter.

Abstract: A radiation source is disclosed comprising a source of charged particles that travel along a path. Target material lies along the path to generate radiation upon impact by the beam. A magnet is provided to deflect the beam prior to impacting the target. The magnet may generate a time-varying magnetic field or a constant magnetic field. A constant magnetic field may be varied spatially across the beam. The magnet may be an electromagnet or a permanent magnet. In one example, deflection of the beam results in impact of the beam on the target along a plurality of axes. In another example, portions of the beam are differentially deflected. The source may thereby irradiate an object to be scanned with more uniform radiation. The charged particles may be electrons or protons and the radiation may be X-ray or gamma ray radiation, or neutrons. Scanning systems incorporating such sources, methods of generating radiation and methods of examining objects are disclosed, as well.

Abstract: An imaging system is disclosed for use in low-light environments or environments where low-levels of such radiation is desirable. Examples of such environments are night photography, laparoscopy, and mammography. In the case of radiation that is other than visible light, a radiation converter and method for fabricating same is disclosed. The radiation converter comprises a film of heavy scintillator (e.g. CdWO4) coated on a fiber optical window to efficiently convert the radiation into visible light. The visible light is passed into a signal amplifier employing an electron-bombarded charge-couple device (EBCCD) to amplify the signal. Novel methods of performing three-dimension imaging using this system as well as removing the effects of high speed movement are also disclosed.

Abstract: A compact X-ray source is disclosed, improving controllability and insulation from unwanted high voltage effects. In one aspect, an active variable conductance device (130, 330) connected in series with the cathode is used in a closed loop, feedback arrangement to control the cathode beam current; the current flowing through the device to the cathode being directly sensed and compared with a desired current level. The result of the comparison is used to control the conductance of the device, thereby directly influencing the cathode current. A second aspect provides an extension of a Faraday cage, whereby the secondary winding of a transformer used to supply power to components within the cage is shielded within a coaxial, tubular member connected to the cage and extending outwardly from it.

Abstract: An X-ray generator comprises an evacuated and sealed X-ray tube, containing an electron gun and an X-ray target. An electron beam is produced by the electron gun in which the cathode is at negative high voltage, the electron gun consisting of a filament just inside the aperture of a Wehnelt grid which is biased negatively with respect to the filament. Two sets of beam deflection coils, are employed in two planes, mounted between the anode of the electron gun and the focussing lens to center the beam. Between the focussing lens and the target is an air-cored quadripole magnet which acts as a stigmator in that it turns the circular cross-section of the beam into an elongated one. This quadripole can be rotated about the tube axis so as to adjust the orientation of the line focus. The beam can be moved about on the target surface by controlling the currents in the four coils of the quadripole.

Abstract: An X-ray tube subsystem including an X-ray tube and a grid voltage supply that reduces high voltage breakdown events. The X-ray tube provides a grid bias connection, a filament bias connection, and an anode bias connection. The grid voltage supply is connected to the grid bias connection and is adapted to produce an ion collection voltage substantially less than an electron beam focus voltage.

Abstract: A scanning electron beam computed tomographic system is provided with a sub-collimation system that passes X-rays emitted by a beam spot formed by an electron beam that is scanned across an X-ray emitting target, which X-rays would not otherwise reach an object under X-ray examination with the system. The sub-collimation system includes phantom-like objects that cause X-rays to be blocked, or passed, through to X-ray detectors depending primarily upon the beam spot position and, secondarily, on the beam-spot shape. Detector output signals may be used in real-time to control at least one characteristic of the electron beam-spot in a closed-loop correction system.

Abstract: A measurement apparatus has a first detector for measuring an intensity such that a sheet-shaped beam of synchrotron radiation is integrated over the entire range of the beam in the thickness direction thereof; a second detector for measuring the intensity of the beam at two points where positions along the direction are different; and a calculating device for calculating the magnitude of the beam in the direction on the basis of the detections by the first and second detectors.

Abstract: A scanning electron beam computed tomographic system is provided with a sub-collimation system that passes X-rays emitted by a beam spot formed by an electron beam that is scanned across an X-ray emitting target, which X-rays would not otherwise reach an object under X-ray examination with the system. The sub-collimation system includes phantom-like objects that cause X-rays to be blocked, or passed, through to X-ray detectors depending primarily upon the beam spot position and, secondarily, on the beam-spot shape. Detector output signals may be used in real-time to control at least one characteristic of the electron beam-spot in a closed-loop correction system.

Abstract: The invention relates to an X-ray system/generator in which after the end of an X-ray exposure the grid of th X-ray tube is blocke4d as long as the X-ray exposure is read out from a detector (or as long a film or a PCR is removed from the X-rays). After read out, the grid is released so that the system capacitance may be discharged via the X-ray tube. Thereby over-exposure due to energy stored in the sytem- and cable capacities is avoided (which is a problem especially for thin objects), and the system may be switched from a tube with grid to a tube without grid without problems.

Abstract: An X-ray beam position monitor has a first plate assembly (1, 3) for detecting the position of the X-ray beam in a horizontal plane and a second plate assembly (6, 8) for detecting the position of the X-ray beam in a vertical plane. The first plate assembly (1, 3) and the second plate assembly (6, 8) are located at the same position along the direction of propagation of the X-ray beam, to provide a compact arrangement suitable for use with X-ray diffractors and for laboratory use.

Abstract: In a method and apparatus for dynamically measuring the position, shape, size and intensity distribution of an effective focal spot of an x-ray tube, wherein at least one of these characteristics changes with respect to time, a detector array is provided that is composed of a number of detector elements, and a micro-hole collimator is disposed between the focal spot and the detector array at a distance closer to the focal spot than to the detector array. An x-ray beam emitted from the focal spot passes through an aperture in the micro-hole collimator, and produces a magnified projection of the focal spot on the detector array. The respective electrical signals from the detector elements of the detector array are sampled, and these sampled signals are combined to dynamically measure the position, shape, size and intensity distribution of the focal spot.

Abstract: An apparatus and method for generating electronically steerable beams of sequential penetrating radiation. Charged particles from a source are formed into a beam and accelerated to a target. Electromagnetic radiation generated by the target is emitted with an angular distribution which is a function of the target thickness and the energy of the particles. A beam of particles is produced by allowing the radiation to exit from an apparatus through a collimator proximal to the target. The direction of the beam is determined by the point of radiation production and the corresponding array of transmission regions of the collimator.

Abstract: Focal spot position determination systems having a high sensitivity to focal spot movement for use in connection with multi-slice computed tomography imaging systems are described. In one embodiment, the determination system is configured for application in a two slice system. Signals from adjacent detector cells in separate rows are compared to determine focal spot position. More particularly, the signal intensity A of the signal output by a first detector cell and the signal intensity B of the signal output by the second detector cell are related to the position of the focal spot. That is, the z position of the centerline of the fan beam can be determined by relating the signal intensities A and B according to the ratio [(A−B)/(A+B)]. Such ratio is representative of the beam location and can be used to control adjustment of the imaging system pre-patient collimator to maintain the beam in the desired position.

Abstract: An x-ray tube has a vacuum housing containing a cathode arrangement that emits electrons and an anode having a target surface on which the electrons, accelerated by an electrical field and forming an electron beam strike in a focal spot, and having a quadrupole magnet system including a coil, for focusing and deflection of the electron beam. A control unit is connected to the quadrupole magnet system. The control unit is supplied with, or has stored therein various parameter sets of predetermined coil currents that can be activated, so that, dependent on the respective parameter set, the focal spot can be displaced discretely in azimuthal fashion onto particular locations of the target surface of the anode.

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: A modular multistage accelerator for use in an X-ray treatment system includes a first 10 kV acceleration stage which houses an electron beam gun supplied with −50 kV of voltage. The modular multi-stage accelerator includes four additional 10 kV stages placed in series with the first stage to achieve a 50 kV accelerator overall. Each stage is shielded to prevent stray electrons from being propagated along the length of the drift tube. The triple point within each modular stage is recessed to significantly reduce the emission of stray electrons within each stage. Additionally, the beam current at the X-ray emitting probe of the X-ray source is measured by isolating the beam current to a beam current measuring circuit in electrical connection with a nulling junction node, wherein other currents within the circuit are nulled at the nulling junction node and the beam current flows to the beam current measuring circuit.

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: A method for scanning an x-ray target in a reverse geometry x-ray imaging system with a charged particle beam is disclosed. An aspect of the invention is directed to scanning patterns for moving an electron beam across the target assembly to generate x-rays, in which a charged particle beam is moved across a plurality of sets of positions on a target assembly, wherein particular positions or sets of positions on the target assembly are rescanned a plurality of times during a single frame. The length of time between a first and a last illumination of the object during the frame is sufficiently small to prevent image blurring during image reconstruction.