EP4163948A1 - Kathodenanordnung - Google Patents

Kathodenanordnung Download PDF

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Publication number
EP4163948A1
EP4163948A1 EP21201742.0A EP21201742A EP4163948A1 EP 4163948 A1 EP4163948 A1 EP 4163948A1 EP 21201742 A EP21201742 A EP 21201742A EP 4163948 A1 EP4163948 A1 EP 4163948A1
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EP
European Patent Office
Prior art keywords
cathode
electron beam
ray source
anode electrode
electrons
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP21201742.0A
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English (en)
French (fr)
Inventor
Ulf LUNDSTRÖM
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Excillum AB
Original Assignee
Excillum AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Excillum AB filed Critical Excillum AB
Priority to EP21201742.0A priority Critical patent/EP4163948A1/de
Publication of EP4163948A1 publication Critical patent/EP4163948A1/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/14—Arrangements for concentrating, focusing, or directing the cathode ray
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H01J35/06—Cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/24—Tubes wherein the point of impact of the cathode ray on the anode or anticathode is movable relative to the surface thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/06—Cathode assembly
    • H01J2235/064—Movement of cathode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/06—Cathode assembly
    • H01J2235/068—Multi-cathode assembly
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/08—Targets (anodes) and X-ray converters
    • H01J2235/081—Target material
    • H01J2235/082—Fluids, e.g. liquids, gases
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08—Electrical details
    • H05G1/26—Measuring, controlling or protecting
    • H05G1/30—Controlling
    • H05G1/52—Target size or shape; Direction of electron beam, e.g. in tubes with one anode and more than one cathode

Definitions

  • the present disclosure relates to a cathode arrangement in an X-ray source, and to a related method.
  • X-ray radiation is generated by interaction between an electron beam and a target.
  • the electron beam is generated by emitting electrons from a cathode and accelerating the emitted electrons towards an anode electrode to form the electron beam.
  • cathode becomes worn after prolonged use, which may lead to uneven electron distribution within the electron beam and/or changes in the electron beam spot size.
  • electrooptical systems in the X-ray source may be used to compensate cathode aging, at least to some degree.
  • the cathode will need to be replaced, either due to failure or as part of preventive maintenance.
  • Replacement of the cathode entails a complete shut-down of the X-ray source, with considerable down-time and a need for trained service personnel to do the replacement.
  • An object of the present disclosure is to provide an X-ray source and a related method which address the above problem.
  • an X-ray source configured to emit X-ray radiation upon interaction between an electron beam and a target in an interaction region, the X-ray source comprising a first and a second cathode each configured to emit electrons; an anode electrode configured to accelerate the emitted electrons to form the electron beam; and an arrangement configured to select one of the first and the second cathode for emission of electrons towards the anode electrode.
  • the arrangement is further configured to ensure that electron beam travels along a pre-defined axis irrespective of which cathode that has been selected.
  • Such X-ray source thus comprises at least two cathodes and an arrangement configured to exchange one cathode for the other when needed.
  • a cathode exchange or replacement can be effected for example by moving a selected cathode into an operating position in which the selected cathode is positioned for emission of electrons towards the anode electrode.
  • a cathode exchange can be effected by moving the anode electrode into a position in which it is aligned with the selected cathode. It is also conceivable that both the cathodes and the anode electrode can be moved during the cathode exchange.
  • the at least two cathodes are mounted in positions selected so that the emitted electrons are directed towards the anode electrode.
  • the arrangement is in this case configured to provide an electromagnetic field directing the electrons emitted from the selected cathode along the pre-defined axis.
  • the two cathodes may be mounted in fixed positions or positional and/or angular adjustments may be allowed e.g., during final assembly, installation, or during maintenance.
  • the new cathode typically needs to be aligned relative to the anode electrode such that electrons emitted from the cathode can be formed into an electron beam.
  • alignment is preferably performed using the same actuator arrangement that is used for replacement of the cathode, i.e. the same actuator arrangement may in some implementations perform both the replacement and the alignment procedures.
  • cathodes having different characteristics may be provided in the X-ray source, thus giving the possibility to alter source performance.
  • the two cathodes may be optimized for different spot sizes, different electron beam currents, or different excitation voltages. In such case, cathode replacement is not necessarily initiated due to wear or failure of the cathode currently in use.
  • the system may keep track of the accumulated operating time of each cathode, e.g. using circuitry such as a timer and/or a memory.
  • the allowed accumulated operating time before a cathode must be replaced can, for example, be based on previous experience.
  • the allowed accumulated operating time may depend on cathode type and may be pre-stored in memory. It is also conceivable that cathode duty cycle is taken into account, e.g. when the cathode is alternately operated continuously and intermittently.
  • a cathode unit may comprise a memory or a counter that records the accumulated operating time of the cathode. Thereby, it can be ensured that a particular cathode is not used beyond its intended service life also in cases where individual cathodes are exchanged between different X-ray sources.
  • this chip may also carry a unique cathode identity thus enabling identification and traceability during the product life cycle.
  • Determining that a cathode replacement is needed can also be based on some measured property of the electron beam (an electron beam quantity), and cathode replacement can be initiated when this property has changed by some predetermined fraction or falls outside of a predetermined allowed range.
  • properties that may be measured include electron beam spot size, intensity distribution over the electron beam cross section, and electron beam divergence.
  • Such electron beam quantities may be measured by scanning the electron beam over a reference surface such as a well-defined edge.
  • the reference surface may be a part of the target or may be a dedicated reference surface separate from the target.
  • Another property that may be measured as an indication of a need for cathode replacement is the temperature or heating current required in order to achieve a certain emission current from the cathode, which typically increases with cathode aging.
  • cathodes in the X-ray source may be replaced by new cathodes.
  • the actuator used for cathode exchange/replacement and alignment may comprise an electrical motor such as a stepper motor.
  • the arrangement for moving the cathodes into the operating position, or for moving the anode electrode, must provide vacuum sealing towards the ambient pressure and allow for the necessary movement.
  • most components could be arranged inside the vacuum chamber of the X-ray source, at least the voltage supply lines to the cathodes typically need to pass through the vacuum enclosure. It may even be advantageous to place the actuator outside of the vacuum chamber to avoid potential problems related to heating, electron bombardment, and outgassing.
  • the cathode may for example be attached to a movable flange provided with an actuator or motor operating on the flange, which in turn may be pivotally connected to a ball joint allowing the flange to move in different directions.
  • the flange may for example be mounted on a translation or rotation stage configured to position a selected one of the cathodes in the operating position, and the flange may also be operably connected to actuators arranged to adjust the orientation of the flange relative a direction of the electron beam.
  • the actuators or motors may in turn be operated or controlled by a controller.
  • a bellows may be provided between the moving parts (flange) and stationary parts (chamber, anode electrode) to ensure vacuum integrity or hermeticity of the chamber.
  • the arrangement may comprise a trajectory correcting component, e.g. one or more coils, designed to provide said electromagnetic field. Currents through the coils are typically controlled by a controller. To allow for mechanical tolerances of the cathode assembly within the X-ray source means may be provided to adjust the position of the respective cathode to achieve the desired alignment between the resulting electron beam and the anode electrode.
  • a trajectory correcting component e.g. one or more coils
  • the distance between the cathodes may need to be at least 3 mm, such as at least 10 mm.
  • Embodiments may thus comprise actuators with sufficient stroke and resolution to provide for both the cathode replacement as well as alignment of the cathode once moved to the operating position.
  • Another exemplary embodiment may comprise a linear stage providing for motion of the cathodes in one direction for cathode replacement, i.e. for moving another cathode into the operating position, and an arrangement for providing angular adjustments of a mounting flange for the cathode assembly. The angular adjustments may be applied to align the cathode, once it has been moved to the operating position, towards an anode aperture.
  • Yet another embodiment may comprise a carousel, e.g. having more than two cathodes where the next cathode may be moved to the operating position by suitable rotation of the carousel.
  • a plurality (such as two) cathodes may be mounted at predetermined fixed positions in the X-ray source, and the anode electrode may be moved so as to align with the selected one of the cathodes.
  • an alignment quantity such as the electron beam location relative to some reference
  • the reference may be comprised within the target or provided as a separate feature. This procedure is, in principle, similar to what is disclosed in WO 2020/094533 .
  • the position or orientation of the cathode at the operating position may be adjusted such that a predetermined alignment condition on the alignment quantity is fulfilled. The adjustment may be performed automatically by the controller by means of an actuator or manually by an operator by means of a setscrew or the like.
  • the cathodes may be connected to one common supply line and one individual supply line each.
  • the voltage supply unit may comprise one output line per cathode and one common line.
  • one set of supply lines is used for all cathodes.
  • the currently active cathode is connected to the supply lines while one or more cathodes not in the operating position is/are disconnected from the supply lines. This may be accomplished with physical attachment and detachment of electrical contacts, an electromechanical switch, or the like.
  • X-ray sources comprising more than one target, or more than one electron beam are conceivable within the scope of the present inventive concept.
  • X-ray sources of the type described herein may advantageously be combined with X-ray optics and/or detectors tailored to specific applications exemplified by but not limited to medical diagnosis, non-destructive testing, lithography, crystal analysis, microscopy, materials science, microscopy surface physics, protein structure determination by X-ray diffraction, X-ray photo spectroscopy (XPS), critical dimension small angle X-ray scattering (CD-SAXS), and X-ray fluorescence (XRF).
  • XPS X-ray photo spectroscopy
  • CD-SAXS critical dimension small angle X-ray scattering
  • XRF X-ray fluorescence
  • a low-pressure chamber, or vacuum chamber 104 may be defined by an enclosure 102 and an X-ray transparent window 106 which separates the low pressure chamber 104 from the ambient atmosphere.
  • the X-ray source 100 comprises a target upon which electrons are incident to generate X-ray radiation.
  • the target may be a solid target or a liquid target.
  • the target is a liquid target and the X-ray source thus comprises a target generator, such as a liquid jet generator 160 configured to form a liquid jet 162 moving along a flow axis passing through an interaction region, or target position I.
  • the liquid jet generator 160 may comprise a nozzle through which liquid, such as e.g. liquid metal may be ejected to form the liquid jet 162 propagating towards and through the interaction region I.
  • the liquid jet 162 propagates through the interaction region I, towards a collecting arrangement 163 arranged below the liquid jet generator 160 with respect to the flow direction.
  • Such solid target may be implemented as a transmission target or a reflection target, including a rotating solid anode.
  • the X-ray source 100 further comprises an electron source 110 configured to provide an electron beam e directed towards the interaction region I.
  • the electron source 110 comprises a cathode and an anode electrode (not shown in Fig. 1 ) for the generation of the electron beam e.
  • the electron beam e interacts with the target, such as the liquid jet 162, to generate X-ray radiation, which is transmitted out of the X-ray source 100 via the X-ray transparent window 106.
  • the X-ray radiation is shown to be transmitted out from the X-ray source 100 in a direction substantially perpendicular to the direction of the electron beam e.
  • the liquid forming the liquid jet is collected by the collecting arrangement 163 and is subsequently recirculated by a pump via a recirculating path 164 to the liquid jet generator 160, where the liquid may be reused to continuously generate the liquid jet 162.
  • a sensor arrangement such as a beam orientation sensor 130 is shown as part of the X-ray source 100.
  • the beam orientation sensor 130 may be configured to monitor a relative position or orientation of the electron beam e and the target 162, and/or a quality measure indicating a performance of the X-ray source.
  • the sensor 130 may be arranged to receive at least part of the electron beam e passing the target 162.
  • the sensor may thus be an electron detector arranged behind the interaction region I as seen from a viewpoint of the electron source 110. In case the target, e.g. the liquid jet 162, moves or changes shape, or in case the electron beam is shifted, at least part of the electron beam e may pass the target 162 and interact with the electron detector 130.
  • the electron detector 130 may monitor a quality measure indicating a relative orientation or alignment of the target 162 and the electron beam e.
  • the X-ray source may comprise a backscatter electron sensor for detecting electrons scattered from the target, a target current detector for detecting an electric current in the target delivered by the incoming electron beam, and/or an X-ray detector for detecting the amount of X-ray radiation generated.
  • a controller, or processing unit 140 is here also illustrated as part of the X-ray source 100.
  • the controller 140 may be arranged inside or outside the low-pressure chamber 104.
  • the controller 140 and the X-ray source 100 may be implemented in a single physical or logical entity, or as communicating parts of a distributed network.
  • the controller receives input from various sensors and is configured to control various parameters of the X-ray source.
  • Fig. 2 is a schematic plan view of an X-ray source 100, which may be similarly configured as the X-ray source shown in Fig. 1 .
  • the X-ray source comprises at least two cathodes 112a, 112b ( Fig. 2 shows also a third cathode 112c) one of which is located at an operating position for emission of electrons towards the anode electrode 114.
  • Each cathode 112 may, for example, be a hot cathode 112 which is heated to create a stream of electrons via thermionic emission, or a thermal-field or cold-field charged-particle source.
  • the emitted electrons may then be accelerated towards the anode electrode 114 by means of an electric field applied between the cathode 112 and the anode electrode 114, and exit the electron source 110 through a hole 115 defined by the anode electrode 114.
  • the anode electrode 114 may form part of an enclosure of the electron source 110, be arranged as a separate element, and/or form part of an arrangement of a plurality of electrodes generating a desired electric field for creating the electron beam e.
  • the orientation of the cathode 112 and the anode electrode 114 may determine the orientation of the electric field that accelerates the emitted electrons.
  • the orientation of the electric field and the position of the aperture 115 through which the resulting electron beam e is emitted from the electron source 110 may in turn define the direction, or trajectory, of the electron beam e.
  • an actuator 120 such as an adjustment screw 120 operated by the controller 140.
  • the adjustment screw 120 may be configured to adjust a position of the cathodes 112 in relation to the anode electrode 114.
  • the adjustment may for example be realized by tilting, or rotating, the cathode 112 so as to change the position from which the electrons are emitted.
  • the actuator may also comprise a translation stage, a carousel or the like to move a selected cathode into the operating position.
  • the actuator 120 is arranged within the vacuum chamber defined by the enclosure 102.
  • the actuator 120 may however in some examples be arranged outside the vacuum chamber, from which it may be accessed without affecting the environment in the vacuum chamber.
  • a more detailed example of an electron source 110 and actuator 120 will be discussed in connection with Fig. 3 .
  • the cathodes are mounted at fixed positions in the X-ray source, and cathode selection is instead effected by moving the anode electrode such that it is aligned with the selected cathode.
  • cathode selection is instead effected by moving the anode electrode such that it is aligned with the selected cathode.
  • Such implementations may be preferred in some cases because fewer mechanical components are needed at the cathodes, which may become very hot during operation.
  • actuators that can be used for aligning the selected cathode and the anode electrode to form the desired electron beam trajectory. In other words, even if the cathodes are mounted at fixed positions, there is typically provided for some movement for alignment purposes.
  • the X-ray source 100 may further comprise electron-optical means 150 configured to adjust the orientation of the electron beam e emitted from the electron source 110.
  • the electron-optical means 150 may for example comprise one or several magnetic and electrostatic lenses and/or deflection plates arranged to act upon the electrons so as to affect their trajectories and thus the shape and orientation of the electron beam e.
  • a correlation between the strength of the applied field and the effect on the electrons can be assumed, which allows for the strength of the applied field to be used as a measure of the degree to which the electron-optical means 150 affects the electron beam.
  • the electron optical means 150 may comprise (see Fig. 4a) a deflection means 154 arranged for deflecting the electron beam in different directions and a focusing means 152 arranged for focusing the electron beam on the target in an electron spot.
  • a size of the electron spot may be adjusted by adjusting a focus setting applied to the focusing means.
  • the electron beam trajectory exiting from the aperture 115 will typically be slightly different for different cathode selections (since the cathodes are mounted at different positions). It may therefore be preferred to have a trajectory correcting component 111, such as a coil or the like, positioned between the aperture 115 and the electron optics 150. The trajectory correcting component may then be configured to ensure that the electron beam enters the electron beam optics 150 at a right angle. Preferably, the electron beam trajectory is along the optical axis of the electron beam optics.
  • the X-ray source comprises at least a first cathode 112a and a second cathode 112b each capable of emitting electrons towards the anode electrode 114.
  • the actuator 120 may be configured to move a selected one of the cathodes 112 into the operating position at which the selected cathode is positioned for emission of electrons towards the anode electrode.
  • the other cathode(s) i.e. the one or more cathodes not located at the operating position, is/are then located at a position away from the operating position.
  • An advantage of this configuration is that a cathode replacement procedure can be conveniently effected when the cathode currently located at the operating position needs to be replaced for another cathode.
  • the cathode 112a at the operating position is then moved away, and another cathode is instead moved into the operating position. In this manner, a cathode replacement can be made without major intervention on the X-ray source.
  • cathode selection is effected by moving the anode electrode 114 such that it is aligned with the selected cathode.
  • Such movement of the anode electrode is preferably a tilting movement that maintains the center of the aperture 115 at a static position to ensure that the electron beam trajectory into the electron optics 150 can be kept the same for different cathode selections.
  • the anode electrode 114 and the cathodes 112 are fixed.
  • the cathodes are provided in individual angles to direct electrons emitted from respective cathode towards anode electrode, in particular towards the center of the aperture 115.
  • a trajectory correcting component 111 is employed to ensure that the outgoing electron beam is directed along the intended trajectory, typically along the optical axis of the electron optics 150.
  • Cathode replacement may be initiated by the controller based on one or more of various inputs. For example, characteristics of the generated X-ray beam may be monitored and if a predetermined condition is met, then cathode replacement may be initiated. Such condition for the generated X-ray beam may be that the X-ray intensity has dropped below a predetermined level in relation to the electron beam power. Another situation in which cathode replacement may be initiated can be that a required alignment of the components of the X-ray source cannot be achieved (which can be caused by a worn cathode).
  • cathode replacement could include that the electron beam has been determined to have a poor beam profile, such as high divergence or low cross-sectional uniformity (which, again, can be caused by a worn cathode). It is also conceivable that the accumulated operating time of each cathode is monitored, and that a cathode replacement is initiated once the operating time exceeds a predetermined value.
  • the X-ray source may comprise a temperature sensor for measuring a temperature of the cathode currently located at the operating position, and cathode replacement may be initiated when the temperature required for a predetermined emission current from the cathode exceeds a predetermined value (it is generally known that cathodes in this context must be operated at increasingly higher temperatures as they wear over time).
  • the electron optics 150 may be controlled by the controller 140 and may hence be used together with the actuator 120 of the electron source 110 to point the electron beam e in a desired direction.
  • the actuator may thus serve a dual purpose of both facilitating the cathode replacement and the alignment of the electron beam.
  • the electron optics 150 may be employed to verify and/or control the relative orientation between the cathode 112 and the anode electrode 114 of the electron source 110.
  • the controller 140 may for example use the actuator 120 and the electron optics 150 in a feedback loop for automatically aligning the electron beam e.
  • the aligning may for example be performed in connection with service or maintenance of the X-ray source 100, and/or regularly during operation of the X-ray source 100 so as to maintain a high performance and to compensate for wear and ageing of the X-ray source 100.
  • FIGs 3a and 3b are schematic illustrations of an electron source 110 according to an embodiment that may be similarly configured as the embodiments discussed above in connection with figures 1 and 2 .
  • the electron source 110 comprises a cathode 112 that is attached to a movable flange 116 that allows for the relative orientation between the cathode 112 and the anode electrode 114 to be varied.
  • the cathode 112 may be movable relative to a housing 119 enclosing the electron-emitting portion of the cathode and the anode electrode 114.
  • the housing 119 may be connected to the enclosure 102 defining the vacuum chamber, and a sealing 117 may be provided between the flange 116 and the housing 119, such as a bellows structure 117 for allowing a relative movement between the flange 116 and the housing 119 without affecting the environment in the vacuum chamber.
  • the orientation of the flange 116 may be varied by actuator 120, such as a first and a second actuator 120 arranged to control an angular orientation of the cathode 112.
  • the actuators 120 are illustrated in the cross section of Fig.
  • actuators include piezoelectric actuators, electromagnetic actuators, linear motors (voice coils), and rotating motors with suitable gear arrangements.
  • the actuators 120 are arranged outside the vacuum chamber. In this configuration the vacuum may be used as a preload for the actuators, i.e. the atmospheric pressure will provide a force on the flange 116 that the actuators 120 must overcome to increase the gap between the flange 116 and wall of the housing 119. As shown in Fig.
  • a reduction of the distance between the upper part of the flange 116 and the housing wall 119 may result in a tilting movement of the cathode 112, such that the position of the electron-emitting part of the cathode 112 is lowered.
  • a reduced distance between the lower part of the flange 116 may result in the electron-emitting part of the cathode 112 being raised to a higher position in relation to the anode electrode 114.
  • Fig. 3b shows a side view of the flange 116 of Fig. 3a , wherein the flange 116 is pivotally connected to the housing 119 via a ball joint 118 (position indicated by a dashed line in Fig. 3b ).
  • the actuators 120 may be arranged to cooperate with the ball joint 118 to provide a desired angular adjustment of the flange 116 around the ball joint 118.
  • displacing the actuators along a common direction it is possible to tilt the flange around an axis passing through the ball and being parallel to a line connecting the two actuators, whereas displacing the actuators in opposite direction gives the ability to tilt the flange around an axis passing through the ball in a direction perpendicular to the line connecting the two actuators.
  • displacing the actuators along the common direction allows for the cathode to be tilted in an upward or downward direction of the figure, whereas displacing the actuators in opposite direction allows for the cathode to be tilted in a sideway direction of the figure.
  • the X-ray source may comprise a sensor for monitoring a quality measure indicating a performance of the X-ray source.
  • the quality measure may for example relate to the characteristics of the generated X-ray radiation, such as intensity or brilliance.
  • the X-ray source may comprise a sensor indicating the interaction between the target and the electron beam e.
  • the interaction may for example be characterized by the number of electrons scattered by the target, absorbed by the target or passing by the same, and the number of secondary electrons present in the chamber.
  • the interaction may also be characterized by the generated X-ray radiation.
  • the above parameters may be used to gain knowledge about the alignment between the target and the electron beam, and to determine how to operate the beam adjustment means and/or the target adjustment means.
  • the parameters may also be used to determine if and when a cathode replacement should be initiated.
  • the X-ray source may comprise a beam orientation sensor 130 arranged behind the target as seen in the direction of the electron beam e.
  • the beam orientation sensor 130 may be used to determine the number of electrons passing by the target, and which therefore not contribute to the generation of X-ray radiation.
  • the number of scattered electrons, or secondary electrons may be detected by electron detectors, such as e.g. electrodes connected to ammeters, arranged within the chamber.
  • the generated X-ray radiation may be measured by X-ray sensitive detectors arranged outside the chamber.
  • These sensors may be connected to the controller 140 so as to provide the controller 140 with information that can be used as feedback in an automated alignment process and/or for an automated cathode replacement procedure as described above.
  • Fig. 4 illustrates an alternative implementation of the actuator for moving cathodes in and out of the operating position.
  • the discussion above has illustrated the actuator as a translation stage, but it is also contemplated to implement the actuator as a revolving stage 400 where the cathodes 410 are moved in and out of the operating position 420 in a rotating fashion. Such configuration may facilitate the inclusion of a larger number of cathodes.
  • a similar mount for the cathodes may also be used for fixed mounting, where cathode selection is made by moving the anode electrode. Having the cathodes positioned at fixed positions around a common center point may then facilitate cathode selection and may also make any subsequent alignment procedure and beam trajectory correction easier.
  • an X-ray source that comprises at least two cathodes each configured to emit electrons when energized, and an anode electrode configured to accelerate the emitted electrons to form an electron beam.
  • the electron beam is directed towards a target for generation of X-ray radiation upon impact on the target.
  • the method can be used for any type of target that is capable of producing X-rays when bombarded with electrons.
  • the target may be a liquid target such as a liquid jet, or a solid target in transmission or reflection, including a rotating solid anode.
  • the method comprises selecting one of the cathodes for emission of electrons towards the anode electrode.
  • This has the advantage that a selected one of the cathodes mounted in the X-ray source can be used for generation of the electron beam.
  • the method can be used for cathode exchange when the currently used cathode is approaching the end of its service life, which can be indicated in various ways as described above.
  • the cathode selection can be effected by moving one of the cathodes into an operating position in which the cathode is positioned for emission of electrons towards the anode electrode.
  • the cathode selection can be effected by moving the anode electrode into a position in which it is aligned with the selected cathode.
  • the cathode selection comprises applying an electromagnetic field directing the electron beam along a pre-defined axis.
  • Various indicators can be used for determining when a cathode replacement is to be initiated. For example, an electron beam quantity indicative of an energy density distribution within the electron beam may be extracted, and a cathode replacement may be initiated when the electron beam quantity fulfils a predetermined electron beam condition. Alternatively, or additionally, an operating time of each respective cathode may be recorded, and cathode replacement may be initiated when the operating time of the cathode currently in use exceeds a predetermined value. Alternatively, or additionally, a temperature of the cathode currently in use may be measured, and cathode replacement may be initiated when the temperature required for a predetermined emission current from the cathode exceeds a predetermined value.

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EP21201742.0A 2021-10-08 2021-10-08 Kathodenanordnung Withdrawn EP4163948A1 (de)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003115398A (ja) * 2001-10-03 2003-04-18 Shimadzu Corp Ｘ線装置
KR20080103286A (ko) * 2007-05-23 2008-11-27 한국전기연구원 탄소나노튜브를 이용한 다중 채널 음극 구조의 마이크로포커싱 엑스-선관
KR20100123987A (ko) * 2009-05-18 2010-11-26 한국전기연구원 냉음극 회전형 전계 방출 소자와 이를 이용한 ｘ선 발생 장치
DE102011007215A1 (de) * 2011-04-12 2012-10-18 Siemens Aktiengesellschaft Elektronenquelle zur Erzeugung eines Elektronenstrahls sowie Röntgenquelle zur Erzeugung von Röntgenstrahlung
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