Cathode device with improved electron emitter contact

Abstract

This invention relates to cathode devices and X-ray sources. A cathode device for an X-ray source according to the invention comprises: - an electron emitter; and - an emitter holder, wherein the electron emitter comprises: - a plurality of parallel-oriented field-effect emitter elements constituting an emitting surface, - a gate electrode disposed above the emitting surface, - and a plurality of first contact elements, characterized in that: - the emitter holder has a plurality of second contact elements, the second contact elements being connectable to the plurality of first contact elements to close a current path, - the plurality of first contact elements being disposed on the side of the plurality of parallel-oriented field-effect emitter elements opposite to the emitting surface.

Description

Technical Field

[0001] This invention relates to a cathode device and an X-ray source. Background Technology

[0002] X-ray sources typically generate X-rays using electrons produced in a vacuum by an electron emitter and then braked upon interaction with an anode after being accelerated by high voltage. Electron emitters used for this purpose can be particularly distinguished as so-called thermionic electron emitters and cold electron emitters. Thermionic electron emitters, in particular, generate electrons by heating the emitter element based on the Edison-Richardson effect. Cold electron emitters, in particular, emit electrons without similar heating, but rather by means of a field-effect emitter element configured accordingly, for example, based on the field effect.

[0003] Conventional electron emitters with field-effect emitter elements are known in particular from US 9,748,071 B2 or EP 3 933881 A1. The former specifically describes the construction of a field-effect emitter element consisting of emitter pins including transistor structures, so as to preferably enable the switching of independent groups of field-effect emitter elements. The latter relates to protective devices to prevent charged particles from impacting the field-effect emitter elements during the operation of such an electron emitter.

[0004] WO 2013 136 299A1 relates to an image detection apparatus comprising an electron-receiving structure and an electron-emitting structure, and further comprising an internal gap providing unobstructed space between the electron-emitting structure and the electron-receiving structure. The image detection apparatus also includes a resistive layer disposed between the electron-emitting structure and the emitter base in a field emission type.

[0005] Compared to thermionic emitter elements, electron emitters with field-effect emitter elements are generally more susceptible to damage or even destruction due to electrical discharge processes within the X-ray source, particularly high-voltage flashovers between the cathode and anode. Such high-voltage flashovers can, for example, cause short circuits between the field-effect emitter elements and the gate electrode. For related effects, see, for example, RFAsadi, T. Zheng, J. Da Silva, G. Rughhoobur, AIAkinwande, and B. Gnade, “Failure Mode of Si Field Emission Arrays based on Emission Pattern Analysis,” 34th International Conference on Vacuum Nanoelectronics (IVNC), Lyon, France, 2021, pp. 1-2, doi: 10.1109 / IVNC52431.2021.9600740. Summary of the Invention

[0006] The purpose of this invention is to provide a cathode device and an X-ray source in which the damage caused by potentially destructive discharge processes can be reduced.

[0007] The objective is achieved through the features of the invention. Advantageous designs are described in the following description.

[0008] Regardless of the grammatical gender of a particular term, people with male or female gender identities are included.

[0009] The cathode device for an X-ray source according to the present invention comprises:

[0010] -Electronic transmitter, and

[0011] - Launcher mount,

[0012] The electron transmitter has the following characteristics:

[0013] - Multiple parallel-oriented field-effect emitter elements, used to form an emission surface on the upper side of the multiple parallel-oriented field-effect emitter elements.

[0014] - Gate electrode positioned above the emitter surface

[0015] - and multiple first contact elements for at least two independent current paths guiding current in the electron emitter.

[0016] - Wherein, based on the emission voltage between the gate electrode and the emitter surface, electrons can be emitted from at least one current path in the current path by means of a field-effect emitter element.

[0017] Its features are,

[0018] The transmitter mount has multiple second contact elements that can be connected to multiple first contact elements to close a current path.

[0019] - Multiple first contact elements are disposed on the side opposite to the emitting surface of multiple parallel-oriented field-effect emitter elements.

[0020] The cathode device according to the invention is particularly advantageous because electron emitters known from the prior art typically involve structural contacts integrated into and / or extending into the emitting surface of the electron emitter. The cathode device according to the invention overcomes these disadvantages by changing the contact from a front-side contact to a non-front-side contact. Destructive discharge processes are preferably reduced because fewer such contact structures, or even none at all, exist in the emitting surface.

[0021] Therefore, the cathode device according to the invention absolutely does not have a structure extending along the emission direction. Thus, the emission direction of the electron emitter is not limited by other accessories. In particular, the focusing unit for the emitted electrons and / or the protective device for preventing the discharge process can be arranged above the electron emitter along the emission direction.

[0022] Another advantage of the cathode device according to the invention involves the possibility that the electron emitter can be oriented and / or inserted relative to the plurality of second contact elements of the emitter seat, especially during the production of the cathode device.

[0023] The X-ray source according to the present invention has:

[0024] - Cathode device

[0025] - Anode, and

[0026] -A vacuum-sealed casing

[0027] The cathode and anode are housed within a vacuum-sealed housing.

[0028] The anode can be either a rotating anode or a stationary anode. In principle, it is possible for the anode to rotate together with the vacuum-sealed housing.

[0029] Electrons generated by means of a cathode device are accelerated from the cathode device toward the anode by means of an accelerating unit. The accelerating unit particularly includes a high-voltage source or a radio frequency source. Depending on the type of accelerating unit, the X-ray source is typically an X-ray emitter, particularly for imaging applications in the keV range, or a linear accelerator, particularly for imaging or therapeutic applications in the MeV range.

[0030] Cathode devices are particularly used to form cathodes for X-ray sources. The cathode potential is typically more negative than the anode potential.

[0031] Electron emitters are particularly configured to generate electrons by means of field-effect emitter elements. Electron emitters are especially independent components, such as electron emitter chips. An electron emitter can, for example, consist of multiple parallel-oriented field-effect emitter elements, a gate electrode, and multiple first contact elements.

[0032] The term "multiple field-effect emitter elements" specifically indicates that there are so many field-effect emitter elements as part of the emitting surface that the emitting surface has a strength of at least 0.1 A / cm. 2 Preferably at least 3A / cm 2 Especially advantageously at least 10A / cm 2 The electron flux density is required. The number of field-effect emitter elements needed for this is typically at least 1000, and usually greater than 1,000,000. Advantageously, the emitting surface has a diameter of at least 0.1 x 0.1 cm. 2 and / or a maximum of 10 by 10 cm 2 The size.

[0033] Field-effect emitter elements can be embedded in an insulating matrix. The insulating matrix preferably holds multiple field-effect emitter elements together.

[0034] Field-effect emitter elements are oriented in particular parallel to and / or flush with the emitting surface. In this case, the emitting surface is advantageously as flat as possible. The emitting surface can, in principle, be further processed to be as flat as possible.

[0035] Field-effect emitter elements typically have an emission point or emission section at the end of the respective field-effect emitter element. The emission surface is particularly formed by the emission point or emission section of the field-effect emitter element. The emission point is, for example, the tip of a field-effect emitter element configured as a field-effect emitter needle. The emission section includes, for example, the emission point and an adjacent region immediately surrounding the emission point.

[0036] The emitting surface is formed on the upper side of multiple field-effect emitter elements. Especially when the gate electrode is not observed and / or when the gate electrode is fully integrated into the volume of the field-effect emitter elements, the upper side of the electron emitter can correspond to the upper side of multiple field-effect emitter elements.

[0037] The sides of a plurality of field-effect emitter elements particularly define the faces of a plurality of field-effect emitter elements and are, in principle, synonymous herein. The sides of a plurality of field-effect emitter elements particularly include upper sides, lower sides, and outer sides. The faces of a plurality of field-effect emitter elements correspondingly include, in particular, an upper surface, a lower surface, and an outer surface, which generally correspond to the emitting surface and generally correspond to the side surface.

[0038] The upper and lower sides of a field-effect emitter element typically have the same dimensions and / or the same geometry. The geometry can be polygonal, especially quadrangular, preferably rectangular, or circular.

[0039] The sides of the multiple parallel-oriented field-effect emitter elements are particularly connected at the top and bottom. The sides of the multiple parallel-oriented field-effect emitter elements are particularly formed by the long side of the outermost field-effect emitter element and / or by the matrix surrounding the outermost field-effect emitter element.

[0040] The sides completely, i.e., cover the circumference of the field-effect emitter element in a 360° manner. If the geometry of the upper side of the field-effect emitter element is circular, then the side is, by definition, an outer surface with a maximum circumference of 90°. If the geometry of the upper side of the field-effect emitter element is polygonal, then the side spans the outer surface from one edge to the adjacent edge, wherein the edges connect the corresponding corners of the upper and lower sides, respectively.

[0041] One option is to grow the field-effect emitter element on a substrate. The substrate can, in principle, be removed after the field-effect emitter element has grown, for example, by grinding it away. The substrate is typically positioned on the underside of the field-effect emitter element.

[0042] Field-effect emitter elements can be configured, for example, as field-effect emitter needles, wherein the tip of the needle forms an emission point, thereby forming an emission surface. Field-effect emitter needles are particularly nanotubes. Alternatively, the field-effect emitter element may form at least one Spindt cathode.

[0043] It is generally feasible to integrate transistor structures, for example, into the field-effect emitter needle, especially when the field-effect emitter needle is made of semiconductors such as silicon, carbon, or molybdenum.

[0044] Field-effect emitter elements can be switched individually, in groups, or all together. Electron emitters that include field-effect emitter elements that can be switched individually or in groups are typically so-called pixelated or segmented emitters. The segmentation of the circuitry of the field-effect emitter elements, and thus the electron emitter, can be achieved by means of different first or second contact elements and / or segmentation of the gate electrode.

[0045] In this application, the current path is defined as a current path that allows all field-effect emitter elements, which can only be switched on or off together, to form their own guiding current. Therefore, depending on the wiring, multiple field-effect emitter elements may include multiple current paths for each field-effect emitter element, some current paths for field-effect emitter elements that can be switched in groups, or a single current path when all field-effect emitter elements can only be switched together. Individually switchable current paths, that is, current paths that can be switched on or off by means of contact elements, are typically current paths that guide current independently of other current paths.

[0046] Typically, each current path is associated with exactly one segment of the electron emitter. These segments of the electron emitter specifically form pixels.

[0047] The gate electrode can be configured as a gitter. The gate electrode is particularly positioned above the emitter surface so that electron emission in the corresponding field-effect emitter element is induced by the field effect through an emission voltage between the gate electrode and the emitter surface. In this context, the term "above" includes the gate electrode being as close as possible to the corresponding field-effect emitter element, for example, directly positioned at the height of the end of the field-effect emitter element that forms the emitter surface and / or surrounding said end of the field-effect emitter element.

[0048] The gate electrode is advantageously configured, for example, to minimize electron emission and / or thermal effects to or on the gate electrode. Alternatively or additionally, the gate electrode is advantageously configured, for example, to maximize electron emission and / or mechanical stability and / or robustness relative to high-voltage flashover to or on the anode.

[0049] The emission voltage is applied, in particular, between the emission point or emission section of the corresponding field-effect element and the gate electrode. For electron emission, typically, the current path from which the electrons for electron emission originate is closed.

[0050] Typically, the gate electrode has a more positive potential than the field-effect emitter element. For example, the gate electrode can be at a constant ground potential while the field-effect emitter element can be at a negative potential. Alternatively, the field-effect emitter element can be at a constant ground potential.

[0051] It is conceivable that the gate electrode can provide different emission voltages to the emitting surface, especially when the gate electrode is configured as a grid. In this case, the gate electrode can be segmented, making the electron emitter a segmented electron emitter. For example, the emission voltage between groups of field-effect emitter elements can be changed by means of segmented gate electrodes, for example, by having different potentials in segments of the gate electrode.

[0052] A plurality of first contact elements and a plurality of second contact elements are specifically configured to establish a secure electrical connection through mutual contact. In particular, the electrical connection can be made via the first contact elements and the second contact elements. In this respect, the electrical connection typically closes the current path here. The plurality of second contact elements are particularly designed as part of the transmitter housing, such that the second contact elements can be connected to the plurality of first contact elements.

[0053] Contact elements may include contact points or contact surfaces. Contact points typically have the smallest possible electrically safe contact surface. It is conceivable that a first contact element has a contact point and a second contact element has a contact surface, wherein the contact point of the first contact element and the contact surface of the second contact element may be connected to each other, or vice versa. Contact surfaces typically have a larger dimension than contact points, such that the two contact elements have a certain gap in a plane relative to each other.

[0054] The field-effect emitter element can be directly connected to multiple first contact elements. The connection between the multiple first contact elements and the field-effect emitter element can be made through the substrate.

[0055] Field-effect emitter elements are connected to current sources, particularly by means of electrically connected contact elements. In this case, the current path extends from the current source through a second contact element, connected to a first contact element, to the field-effect emitter element.

[0056] Consideration may be made to the first contact element being connected to one or more field-effect emitter elements. The second contact element may be connectable to one or more of the first contact elements. The number of first and second contact elements may be the same or may vary.

[0057] Multiple contact elements specifically refer to the presence of at least one order of magnitude fewer first or second contact elements than the number of field-effect emitter pins. In principle, it can be considered that the number of first contact elements corresponds to the number of field-effect emitter pins.

[0058] Typically, the number of first contact elements is related to the number of current paths. Multiple first contact elements for at least two independently guiding current paths in an electron emitter are particularly conductively connected to at least two current paths. The at least two current paths of the electron emitter may include only the current path of the field-effect emitter element, or additionally include another current path of the electron emitter, such as another current path of the gate electrode, for the current path of the field-effect emitter element.

[0059] Connectability specifically means electrical connectivity, i.e., establishing an electrical connection. Electrical connectivity specifically means electrical contact.

[0060] Depending on the design of the cathode device, the connectable contact elements can be electrically connected. Unconnected contact elements, in particular, do not close their respective current paths; rather, the current paths are open. In principle, the first and second contact elements can be connected in the same way or interchanged.

[0061] Transmitter mounts typically have a fixing mechanism to secure and / or orient the electron transmitter at the mount. The transmitter mount particularly has a carrier at which a second contact element is fixed. The carrier and the second contact element are typically electrically separated. The second contact element is particularly located on the side of the transmitter mount, especially the carrier, facing the electron transmitter.

[0062] The emitter holder, particularly the carrier, can be configured as a focusing head for emitting electrons. The emitter holder, particularly the carrier, can be designed to be metallically, and particularly additionally, electrically conductive, for example, at a negative high voltage potential or ground potential. The emitter holder can be designed to extend the current path of the field-effect emitter element to a current source, thereby enabling a connection between the field-effect emitter element and the current source. For this purpose, the emitter holder may, for example, have at least one wire connecting the field-effect emitter element to the current source.

[0063] The side opposite to the emitting surface is in particular not the upper surface or the upper side. The side opposite to the emitting surface can in particular be the lower side and / or the outer side. Specifically, the plurality of second contact elements do not face the emitting surface, but rather face the plurality of first contact elements. If the plurality of first contact elements face the plurality of second contact elements, then the first contact elements and the second contact elements are generally connectable.

[0064] One embodiment proposes that a plurality of first contact elements are disposed only on the opposite side. This embodiment is particularly advantageous due to its compactness.

[0065] One embodiment proposes that the side opposite to the emitting surface is the lower side of a plurality of parallel-oriented field-effect emitter elements, which are opposite to the emitting surface and face the emitter mount. This embodiment is particularly advantageous because it allows for contact with the plurality of parallel-oriented field-effect emitter elements from below.

[0066] One embodiment proposes that the first contact element is disposed only within the first plane. This, in particular, simplifies the contact of the field-effect emitter element. "Only" means that no first contact element is disposed outside the first plane.

[0067] One embodiment proposes that a plurality of second contact elements are disposed only within the second plane. This, in particular, simplifies the provision of contacts for the field-effect emitter elements. "Only" means that no second contact elements are disposed outside the second plane.

[0068] One implementation proposes that the first and second planes are oriented parallel to each other. This implementation advantageously allows for relatively simple contact.

[0069] One embodiment proposes that, for connection, a plurality of second contact elements and / or a plurality of first contact elements are movably designed. This embodiment is particularly advantageous because contact can be made and disengaged by means of movable contact elements. In other words, the movable design advantageously enables the connection of connectable contact elements, especially without changing the orientation of the electron transmitter relative to the transmitter mount. In particular, the plurality of second contact elements are designed to be movable relative to the transmitter mount for connection with the plurality of first contact elements and / or the plurality of first contact elements are designed to be movable relative to the electron transmitter for connection with the plurality of second contact elements. The movable design can be implemented individually for single or grouped contact elements, or jointly for all first contact elements and / or all second contact elements.

[0070] One embodiment proposes that the movable design is achieved by means of a resilient connecting element. This embodiment is particularly advantageous for establishing an electrically safe and equally flexible connection. In particular, at least one resilient connecting element has a mechanical force transmitter, which is a push pin or a spring pin. Multiple push pins and / or spring pins can be part of the movable design of the contact element. Depending on the type of movable design, multiple resilient connecting elements can be provided, particularly individually or in groups, for single contact elements.

[0071] One embodiment proposes that a plurality of second contact elements are connected to a plurality of first contact elements only in a force-fit and / or form-fit manner. The plurality of second contact elements are connected to the plurality of first contact elements particularly in a non-material-fit manner, i.e., particularly in a non-welding manner. This embodiment particularly provides the advantage of reversible contact, which allows for the replacement of the electron emitter without removing the emitter holder from the cathode device or X-ray source.

[0072] One embodiment proposes that a plurality of first contact elements are arranged according to a BGA ball grid arrangement. In this case, a plurality of second contact elements are also typically arranged according to a BGA ball grid arrangement. This embodiment is particularly advantageous due to the use of a standardized arrangement of a plurality of first and / or second contact elements.

[0073] One embodiment proposes that the contact surface of one of the plurality of first contact elements and the contact surface of one of the plurality of second contact elements have different areas. In other words, the area of ​​one of the plurality of first contact elements and the area of ​​one of the plurality of second contact elements are different. For example, it may be conceivable that one of the contact surfaces is a contact point, so that the smaller of the two areas approximates only the area required for a safe electrical connection.

[0074] Features, advantages, or alternative implementations mentioned in the description of the device can also be applied to the method, and vice versa. In other words, embodiments of the method can be improved with the help of features of the device, and vice versa. In particular, the device according to the invention can be used in the method. Attached Figure Description

[0075] The invention is described and illustrated in more detail below with reference to the embodiments shown in the accompanying drawings. In principle, the same structures and units are retained in the following description of the drawings and named with the same reference numerals as when the corresponding structures or units first appear.

[0076] The attached diagram shows:

[0077] Figure 1 A cathode device according to the present invention is shown;

[0078] Figure 2 The cathode device of the first embodiment is shown;

[0079] Figure 3 The X-ray source is shown. Detailed Implementation

[0080] Figure 1 A schematic cross-sectional view of a cathode device 30 according to the present invention is shown. The cathode device 30 includes an electron emitter 10 and an emitter mount 20.

[0081] The electron emitter 10 has a plurality of parallel-oriented field-effect emitter elements 11, forming an emission surface 12 on the upper side of the plurality of parallel-oriented field-effect emitter elements 11. The field-effect emitter elements 11 are disposed on an optional substrate. The emission surface 12 is perpendicular to the [missing information - likely a specific orientation or direction]. Figure 1 The drawing plane is represented by dashed lines.

[0082] The electron emitter 10 also has a gate electrode 13 disposed above the emitting surface 12. The gate electrode 13 is configured as a grid. The grid is disposed as close as possible to the end of the field-effect emitter element 11.

[0083] Additionally, the electron transmitter 10 has a plurality of first contact elements 14 for at least two independent current paths guiding current in the electron transmitter 10. The plurality of first contact elements 14 in Figure 1 It is fixed in the middle position.

[0084] Figure 1 The first current path includes four field-effect emitter elements 11, and the second current path includes four additional field-effect emitter elements 11, which can be connected to individual second contact elements 21 via individual first contact elements 14. Therefore, Figure 1 The electron transmitter 10 is a so-called segmented or pixelated transmitter.

[0085] The transmitter mount 20 has a plurality of second contact elements 21, which can be connected to a plurality of first contact elements 14 and Figure 1 Electrical connections are made to close the current path. Based on the emission voltage between the gate electrode 13 and the emitter surface 12, and especially the electrical connections between the contact elements 14, 21, electrons can be emitted from at least one of the current paths by means of the field-effect emitter element 11.

[0086] Multiple first contact elements 14 are disposed on the side of multiple parallel-oriented field-effect emitter elements 12 opposite to the emitting surface 12. Figure 1 In the cathode device 30, a plurality of first contact elements 14 are disposed only on the opposite side, wherein the side opposite to the emitting surface 12 is the lower side of a plurality of parallel oriented field effect emitter elements 11 opposite to the emitting surface 12 and facing the emitter base 20.

[0087] The first contact element 14 is disposed only in the first plane. A plurality of second contact elements 21 are disposed only in the second plane. The first and second planes are oriented parallel to each other. The plurality of first contact elements 14 are advantageously arranged according to a BGA ball grid arrangement.

[0088] The contact surface of one of the multiple first contact elements 14 and the contact surface of one of the multiple second contact elements 21 have different areas. Each of the multiple second contact elements 21 has a contact point such that its area is smaller than the area of ​​the multiple first contact elements 14 to which it belongs.

[0089] Figure 2 A schematic cross-sectional view of a first embodiment of the cathode device 30 is shown.

[0090] The transmitter mount 20 has a carrier 22. For connection, a plurality of second contact elements 21 are movably designed relative to the carrier 22. Alternatively or additionally, a plurality of first contact elements 14 may be movably designed relative to the field-effect transmitter element 11.

[0091] Another current path in at least two independent current paths has a gate electrode 13 and one of a plurality of second contact elements 21. The current path additionally has another first contact element 14. A segment of the gate electrode 13 may form the other first contact element 14.

[0092] The movable design is achieved by means of flexible connecting elements, at least one of which has a mechanical force transmitter, namely a press pin or a spring pin. A plurality of second contact elements 21 are connected to a plurality of first contact elements 14 in a force-fit manner only. Alternatively or additionally, a form-fit connection may be considered.

[0093] Figure 3 A schematic longitudinal section of the X-ray source 40 is shown.

[0094] The X-ray source 40 has a cathode device 30, an anode 41, and a vacuum-sealed housing 42. The cathode device 30 and the anode 41 are disposed within the vacuum-sealed housing 42.

[0095] Although the details of the invention have been described and illustrated in detail through preferred embodiments, the invention is not limited to the disclosed examples and other variations can be derived by those skilled in the art without departing from the scope of protection of the invention.

Claims

1. A cathode device (30) for an X-ray source (40), comprising: - Electron transmitter (10), and - Launcher mount (20). The electron transmitter (10) described therein has: - A plurality of parallel-oriented field-effect emitter elements (11) for forming an emission surface (12) on the upper side of the plurality of parallel-oriented field-effect emitter elements (11). - Gate electrode (13) disposed above the emitter surface (12). - and a plurality of first contact elements (14) for at least two independent current paths for guiding current in the electron transmitter (10). - Wherein, based on the emission voltage between the gate electrode (13) and the emission surface (12), electrons can be emitted from at least one of the current paths by means of the field-effect emitter element (11). Its features are, - The transmitter base (20) has a plurality of second contact elements (21) that can be connected to the plurality of first contact elements (14) to close the current path. - The plurality of first contact elements (14) are disposed on the side of the plurality of parallel-oriented field effect emitter elements (11) opposite to the emitting surface (12).

2. The cathode device (30) according to claim 1. The plurality of first contact elements (14) are provided only on the opposite side.

3. The cathode device (30) according to claim 1 or 2. The side opposite to the emitting surface (12) is the lower side of the plurality of parallel-oriented field-effect emitter elements (11) that are opposite to the emitting surface (12) and facing the emitter base (20).

4. The cathode device (30) according to claim 1 or 2. The first contact element (14) is only disposed in the first plane.

5. The cathode device (30) according to claim 4. The plurality of second contact elements (21) are disposed only in the second plane.

6. The cathode device (30) according to claim 5. The first plane and the second plane are oriented parallel to each other.

7. The cathode device (30) according to claim 1 or 2. For the purpose of connection, the plurality of second contact elements and / or the plurality of first contact elements are movably designed.

8. The cathode device (30) according to claim 7. The movable design is achieved through flexible connecting elements.

9. The cathode device (30) according to claim 8. At least one of the elastic connecting elements has a mechanical force transmitter.

10. The cathode device (30) according to claim 9. The force transmitter of the machine is a push pin or a spring pin.

11. The cathode device (30) according to claim 1 or 2. The plurality of second contact elements (21) are connected to the plurality of first contact elements (14) only in a force-fit and / or form-fit manner.

12. The cathode device (30) according to claim 1 or 2. The plurality of first contact elements (14) are arranged according to a BGA ball grid arrangement.

13. The cathode device (30) according to claim 1 or 2. The other current path of the at least two independent current paths has one of the gate electrode (13) and one of the plurality of second contact elements (21).

14. The cathode device (30) according to claim 1 or 2. The contact surface of one of the plurality of first contact elements (14) and the contact surface of one of the plurality of second contact elements (21) have different areas.

15. An X-ray source (40) having: - Cathode device (30) according to any one of claims 1 to 14. - Anode (41), and - Vacuum-sealed shell (42). The cathode device (30) and the anode (41) are disposed within the vacuum-sealed housing (42).

Images