X-RAY TUBE WITH A COOLED GATE ELECTRODE

Abstract

An X-ray tube includes a tube body that encloses a tube volume in a gas-tight manner. An emitter electrode, a gate electrode, and an anode are arranged within the tube volume. The emitter electrode is an unheated electrode having emitter needles in an area facing the gate electrode, which are themselves arranged on a substrate. The arrangement of the emitter electrode and the gate electrode are coordinated such that applying an emission voltage between the emitter electrode and the gate electrode causes electrons to be emitted from the multitude of emitter needles due to the resulting electrical field. The gate electrode is connected with thermal conductivity via a connecting element to a heat sink arranged outside the tube volume.

Claims

1. An X-ray tube, comprising: a tube body enclosing a tube volume in a gas-tight manner; and an emitter electrode, a gate electrode, and an anode arranged within the tube volume; wherein the emitter electrode is an unheated electrode, which has a multitude of emitter needles in an area facing the gate electrode, the multitude of emitter needles being arranged on a substrate, an arrangement of the emitter electrode and the gate electrode is coordinated such that applying an emission voltage between the emitter electrode and the gate electrode causes electrons to be emitted from the multitude of emitter needles due to a resulting electrical field, the gate electrode is connected, with thermal conductivity via a connecting element, to a heat sink arranged outside the tube volume, the multitude of emitter needles are embedded in a layer such that the layer mechanically stabilizes the multitude of emitter needles, and the layer is a thermally conductive layer.

2. The X-ray tube as claimed in claim 1, wherein the layer is connected to the gate electrode.

3. The X-ray tube as claimed in claim 2, wherein the gate electrode has pins on a side facing the emitter electrode, the pins run parallel to a longitudinal extension of the multitude of emitter needles, and the pins are embedded in the layer between the multitude of emitter needles such that the pins are connected to the layer with thermal conductivity.

4. The X-ray tube as claimed in claim 2, wherein the gate electrode is connected, via the connecting element, to the heat sink with thermal conductivity and with electrical conductivity, and the layer includes a material that is electrically insulating at room temperature and electrically conductive from a limit temperature above room temperature.

5. The X-ray tube as claimed in claim 4, wherein the layer includes a semiconductor material with a band gap that is larger than a band gap of a material used for the multitude of emitter needles, or the layer is a p-doped or n-doped insulator.

6. The X-ray tube as claimed in claim 4, further comprising: a measuring device configured to measure a current flowing, via the connecting element, from the gate electrode to the heat sink; wherein a voltage regulating device is allocated to the X-ray tube, the voltage regulating device being configured to receive a measured value for the current measured by the measuring device, and to influence an emission voltage present between the emitter electrode and the gate electrode subject to the current.

7. The X-ray tube as claimed in claim 1, wherein the layer has a thermal conductivity that is higher than a thermal conductivity of silicon dioxide.

8. The X-ray tube as claimed in claim 1, wherein the layer includes silicon dioxide or a plastic-based material.

9. The X-ray tube as claimed in claim 1, wherein the multitude of emitter needles form multiple individually controllable groups.

10. The X-ray tube as claimed in claim 1, wherein the multitude of emitter needles include silicon.

11. The X-ray tube as claimed in claim 1, wherein the connecting element includes a metal or metal alloy.

12. The X-ray tube as claimed in claim 1, wherein the heat sink is a support structure made from metal and is configured to support the tube body, or is an independent element distinct from a support structure, or the tube body forms the heat sink.

13. The X-ray tube as claimed in claim 1, wherein the gate electrode and the heat sink are configured such that heat is dissipated from the gate electrode and fed to the heat sink via a coolant carried in a cooling channel, the cooling channel is a closed circuit between the gate electrode and the heat sink, and the cooling channel is at least one of encompassed by the connecting element or arranged on the connecting element.

14. The X-ray tube as claimed in claim 8, wherein the plastic-based material is a resin.

15. The X-ray tube as claimed in claim 1, wherein the connecting element includes copper.

16. The X-ray tube as claimed in claim 12, wherein the metal is steel or aluminum.

17. The X-ray tube as claimed in claim 3, wherein the gate electrode is connected, via the connecting element, to the heat sink with thermal conductivity and with electrical conductivity, and the layer includes a material that is electrically insulating at room temperature and electrically conductive from a limit temperature above room temperature.

18. The X-ray tube as claimed in claim 5, further comprising: a measuring device configured to measure a current flowing, via the connecting element, from the gate electrode to the heat sink; wherein a voltage regulating device is allocated to the X-ray tube, the voltage regulating device being configured to receive a measured value for the current measured by the measuring device, and to influence an emission voltage present between the emitter electrode and the gate electrode subject to the current.

19. The X-ray tube as claimed in claim 18, wherein the layer has a thermal conductivity that is higher than a thermal conductivity of silicon dioxide.

20. The X-ray tube as claimed in claim 18, wherein the multitude of emitter needles form multiple individually controllable groups.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The characteristics, features, and advantages of this invention described above, as well as the manner in which they are achieved, become clearer and more understandable in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawings. Schematic representations are provided as follows:

[0039] FIG. 1 an X-ray tube,

[0040] FIG. 2 an X-ray tube, which is held in a support structure,

[0041] FIG. 3 an electrode arrangement,

[0042] FIG. 4 groups of emitter needles and their control,

[0043] FIG. 5 a section of an emitter electrode, a gate electrode, and a thermally conductive layer,

[0044] FIG. 6 a block diagram and

[0045] FIG. 7 a gate electrode, a heat sink, and a connecting element.

DETAILED DESCRIPTION

[0046] According to FIG. 1, an X-ray tube 1 has a tube body 2. The tube body 2 can consist of glass, for example. The tube body 2 encloses a tube volume 3 in a gas-tight manner. The tube volume 3 is evacuated. An emitter electrode 4, a gate electrode 5, and an anode 6 are arranged within the tube volume 3 (amongst other things). The gate electrode 5 is arranged between the emitter electrode 4 and the anode 6, usually in the immediate vicinity of the emitter electrode 4. The gate electrode 5 is usually embodied in a grid-like manner. The anode 6 can be embodied as a conventional rotating anode. The electrodes 4 and 6 are connected to electronics arranged outside the tube volume 3 via electrical wires (not shown). During operation, the emitter electrode 4 emits electrons 7, which are accelerated toward the anode 6 by high voltage present between the emitter electrode 4 and the anode 6 and generate X-rays 8 there.

[0047] The gate electrode 5 is connected with thermal conductivity via a connecting element 9 to a heat sink 10. The heat sink 10 is arranged outside the tube volume 3. In accordance with the schematic representation in FIG. 2, the heat sink 10 can be embodied as a support structure 11, which supports the X-ray tube 1. Alternatively, in accordance with the schematic representation in FIG. 1, the heat sink 10 can be an independent element distinct from the support structure 11. In the former instance, the heat sink 10 usually consists of metal, particularly steel or aluminum. In the latter instance, the heat sink 10 usually consists of metal, predominantly aluminum. In both instances, the heat sink 10 can be embodied in such a way that it has the largest possible cooling surface to the surroundings. For example, the heat sink 10 can have cooling ribs. Furthermore, the tube body 2 itself can also act as a heat sink 10.

[0048] It is particularly preferably for the gate electrode 5 to be connected to the heat sink 10 via the connecting element 9 not only with thermal conductivity but also with electrical conductivity. For example, the connecting element 9 can consist of a metal or metal alloy, particularly copper, but also aluminum in individual cases. The heat sink 10 and thus also the gate electrode 5 are preferably connected to the constant ground potential. If the tube body 2 forms the heat sink 10, the tube body 2 can be coated on the outside with a metal layer, for example.

[0049] According to FIG. 3, the emitter electrode 4 is embodied as an unheated electrode, thus as a so-called cold emitter. It has a multitude of emitter needles 12 in an area facing the gate electrode 5. The emitter needles 12 are themselves arranged on a substrate 13. The emitter needles 12 preferably consist of a silicon Si. The arrangement of the emitter electrode 4 and of the gate electrode 5 are coordinated in such a way that applying an emission voltage U between the emitter electrode 4 and the gate electrode 5 causes electrons to be emitted from the emitter needles 12 due to the resulting electrical field. If the emission voltage U between the emitter needles 12 of the emitter electrode 4 and the gate electrode 5 is high enough, the emitter needles 12 thus emit free electrons in the area between the emitter needles 12 and the gate electrode 5, so that these electrons can then be accelerated toward the anode 6.

[0050] It is possible that the emitter needles 12 are always controlled uniformly. In accordance with the representation in FIG. 4, however, the emitter needles 12 preferably form individually controllable groups. Each group of emitter needles 12 can be supplied with its own operating voltage U. The number of groups of emitter needles 12 shown in FIG. 4 is purely an example. Considerably more than the two groups of emitter needles 12 shown are usually present. Likewise, the number of emitter needles 12 shown per group in FIG. 4 is also purely an example. The groups usually comprise considerably more emitter needles 12.

[0051] In accordance with the representation in FIG. 3, the emitter needles 12 are preferably embedded in a layer 14. The layer 14 preferably has good thermal conductivity. It is possible for the layer 14 to consist of silicon dioxide (SiO2) or a plastic-based material, particularly a resin. In both these cases, the thermally conductive layer 14 is always electrically insulating regardless of its temperature. The layer 14 can also consist of other materials. In this instance, the layer 14 can in particular have thermal conductivity that is higher than the thermal conductivity of silicon dioxide.

[0052] The layer 14 is preferably connected to the gate electrode 5, see, for example, according to FIG. 3 with thermal conductivity from the emitter needles 12 via the layer 14 to the gate electrode 5. In particular, the gate electrode 5 can have pins 15 on its side facing the emitter electrode 4 in accordance with the representation in FIG. 5. The pins 15 run in this instance in parallel to a longitudinal extension of the emitter needles 12. They are embedded between the emitter needles 12 in the thermally conductive layer 14. In the case of the thermally conductive, and thus in particular also mechanical, connection of the thermally conductive layer 14 and the gate electrode 5, the thermally conductive layer 14 preferably consists of a material that is electrically insulating at room temperature and electrically conductive from a limit temperature above room temperature. For example, the thermally conductive layer 14 can consist of a semiconductor material with a large band gap or can be embodied as a p-doped or n-doped insulator.

[0053] The gate electrode 5 must be open. This is because the area above the points of the emitter needles 12 must remain clear, as otherwise the electrons could not be sucked away toward the anode 6. The gate electrode 5 is thus only arranged between the points of the emitter needles 12 and has breakthroughs or openings above the points of the emitter needles 12. The layer 14 in contrast can be adjacent to the underside of the gate electrode 5.

[0054] In the event that the layer 14 is embodied in such a way that it is electrically conductive above the limit temperature, the X-ray tube 1 preferably has a measuring device 16 according to FIG. 6. The measuring device 16 is used to measure a current I, which flows via the connecting element 9 from the gate electrode 5 to the heat sink 10. A voltage regulating device 17 is also allocated to the X-ray tube 1 in this instance. A measured value for the current I recorded using the measuring device 16 is fed to the voltage regulating device 17. The voltage regulating device 17 influences in this instance the emission voltage U present between the emitter electrode 4 and the gate electrode 5 subject to the current I.

[0055] In order to optimize the cooling of the gate electrode 5, it is possible for the gate electrode 5 and the heat sink 10 to be embodied as hollow parts in accordance with the representation in FIG. 7. In this instance, the gate electrode 5 and the heat sink 10 are connected to each other via wires 18, which are arranged in the connecting element 9. As a result, a coolant 19 is able to circulate in a closed circuit from the gate electrode 5 to the heat sink 10 and back.

[0056] Embodiments of the present invention have many advantages. In particular, a higher current density can be achieved by cooling the emitter electrode 4. This is particularly advantageous in connection with a cold emitter. Due to the possibility of providing multiple groups of emitter needles 12 with the cold emitter, the X-rays can also be influenced through position-dependent control of the emitter electrode 4.

[0057] The drawings are to be regarded as being schematic representations and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose become apparent to a person skilled in the art. Any connection or coupling between functional blocks, devices, components, or other physical or functional units shown in the drawings or described herein may also be implemented by an indirect connection or coupling. A coupling between components may also be established over a wireless connection. Functional blocks may be implemented in hardware, firmware, software, or a combination thereof.

[0058] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections, should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of embodiments. As used herein, the term and/or, includes any and all combinations of one or more of the associated listed items. The phrase at least one of has the same meaning as and/or.

[0059] Spatially relative terms, such as beneath, below, lower, under, above, upper, and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as below, beneath, or under, other elements or features would then be oriented above the other elements or features. Thus, the example terms below and under may encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. In addition, when an element is referred to as being between two elements, the element may be the only element between the two elements, or one or more other intervening elements may be present.

[0060] Spatial and functional relationships between elements (for example, between modules) are described using various terms, including on, connected, engaged, interfaced, and coupled. Unless explicitly described as being direct, when a relationship between first and second elements is described in the disclosure, that relationship encompasses a direct relationship where no other intervening elements are present between the first and second elements, and also an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. In contrast, when an element is referred to as being directly connected, engaged, interfaced, or coupled to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., between, versus directly between, adjacent, versus directly adjacent, etc.).

[0061] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the embodiments. As used herein, the singular forms a, an, and the, are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the terms and/or and at least one of include any and all combinations of one or more of the associated listed items. It will be further understood that the terms comprises, comprising, includes, and/or including, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term and/or includes any and all combinations of one or more of the associated listed items. Expressions such as at least one of, when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. Also, the term example is intended to refer to an example or illustration.

[0062] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.

[0063] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0064] It is noted that some embodiments may be described with reference to acts and symbolic representations of operations (e.g., in the form of flow charts, flow diagrams, data flow diagrams, structure diagrams, block diagrams, etc.) that may be implemented in conjunction with units and/or devices discussed above. Although discussed in a particularly manner, a function or operation specified in a specific block may be performed differently from the flow specified in a flowchart, flow diagram, etc. For example, functions or operations illustrated as being performed serially in two consecutive blocks may actually be performed simultaneously, or in some cases be performed in reverse order. Although the flowcharts describe the operations as sequential processes, many of the operations may be performed in parallel, concurrently or simultaneously. In addition, the order of operations may be re-arranged. The processes may be terminated when their operations are completed, but may also have additional steps not included in the figure. The processes may correspond to methods, functions, procedures, subroutines, subprograms, etc.

[0065] Specific structural and functional details disclosed herein are merely representative for purposes of describing embodiments. The present invention may, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein.

[0066] Although the present invention has been illustrated and described in more detail by preferred exemplary embodiments, this shall not limit the present invention to the disclosed examples, and other variations may be deduced from these by the person skilled in the art without extending beyond the scope of protection of the present invention.

[0067] Independent of the grammatical term usage, individuals with male, female or other gender identities are included within the term.