Electron gun device

Abstract

To provide an electron gun to be improved in regard to a cost and / or assembling labor.SOLUTION: An electron gun device (10) for, specifically, an X-ray pipe (12), comprises: a first metal electrode (14) having a first electrode contact surface (16); a second metal electrode (18) having a second electrode contact surface (20); and an annular ceramic insulation body (22). The annular ceramic insulation body (22) includes: a first insulation body contact surface (24) on a first side to a shaft direction (26) of an insulation body (22); and a second insulation body contact surface (28) to a second side that is opposite to the shaft direction (26). In an assembling state, the first insulation body contact surface (24) is faced to the first electrode contact surface (16), and is connected to the first electrode contact surface (16) via a first soldering bond (30). The second insulation body contact surface (28) is faced to the second electrode contact surface (20), and is connected to the second electrode contact surface (20) via a second soldering bond (32).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an electron gun device according to claim 1, an X-ray tube according to claim 12, and a method for assembling the electron gun device according to claim 13.

Background Art

[0002] Known electron guns for use in X-ray tubes often include a number of electrodes held together by rod-shaped isolators along the length of the assembled part. These isolators are usually made of glass or, rarely, ceramics. Achieving the required accuracy during assembly is difficult and time-consuming. Furthermore, the quality control procedures are complex.

Summary of the Invention

Means for Solving the Problems

[0003] An object of the present invention is to provide an improved electron gun, particularly with regard to cost and / or assembly effort. According to the present invention, this object is achieved by the features according to claims 1, 12 and 13, but advantageous embodiments and further developments of the present invention can be obtained from the dependent claims.

[0004] An electron gun device, particularly for an X-ray tube, preferably for an X-ray microfocus tube, comprising a first electrode made of metal having a first electrode contact surface, a second electrode made of metal having a second electrode contact surface, an annular ceramic insulator having a first insulator contact surface on a first side with respect to the axial direction of the insulator and a second insulator contact surface on a second side opposite to the axial direction, wherein, in the assembled state, the first insulator contact surface faces the first electrode contact surface and is connected to the first electrode contact surface via a first brazed joint, and the second insulator contact surface faces the second electrode contact surface and is connected to the second electrode contact surface via a second brazed joint. is proposed.

[0005] According to the present invention, an improved electron gun device can be provided. In particular, with regard to the materials used and the stability of the manufacturing process, costs can be reduced and the assembly can be simplified. The electron gun device according to the present invention is mechanically stable and exhibits good thermal and electrical performance and stability.

[0006] The electron gun device is in particular part of an electron gun, preferably a subassembly. Alternatively, the electron gun can also be embodied by the electron gun device. The electron gun and / or the electron gun device is advantageously part of an X-ray tube, preferably an X-ray microfocus tube, for generating X-rays. The electron gun and / or the electron gun device is intended to generate free electrons and in particular to emit these free electrons along an electron beam direction parallel to the axial direction. The electron gun device may comprise an electron emitter for emitting electrons and may further comprise a connection unit for connecting a high voltage for accelerating the electrons. The electrical contacts within the connection unit can be made in any conceivable way, for example by soldering, welding, clamping and / or crimping. The X-ray tube may comprise an electron tube in which the electron gun device can be at least partially arranged, and / or a high voltage source for supplying a high voltage and / or in particular a target head, preferably made of tungsten, arranged in particular adjacent to the electron tube and for generating X-rays via electrons hitting the target, in particular an anode target head.

[0007] Any type of electron emitter is conceivable, but preferably, in particular, an oxide-coated dispenser cathode made from a porous tungsten block impregnated with BaO (barium oxide) which reduces the work function of pure tungsten and enables the emitter to function at a much lower temperature compared to pure tungsten is used. Here, the actual emitter surface may be heated indirectly by a heating filament potted with alumina. Alternatively, the electron emitter is a simple tungsten or tungsten-rhenium filament, and LaB6 or CeB 6 (Lanthanum hexaboride or cerium hexaboride) crystal emitters can also be included. In yet another alternative, a field effect emitter is also conceivable.

[0008] During operation, the electrode emitter is in electrical contact, in particular as a cathode, preferably at a potential of -3 kV to -0.5 kV, especially via the connection unit. The electron gun preferably comprises a third electrode made of metal that can be electrically connected to the electrode emitter. Thus, the third electrode and the electrode emitter can together form a cathode during operation, preferably at a common potential of -3 kV to -0.5 kV. The third electrode may be in the shape of a disk, preferably a circular disk, but in particular recesses and / or notches for the conductors of the electron gun device are conceivable.

[0009] The first electrode may in particular be a grid electrode for the purpose of controlling the electron beam, and the grid electrode may be at a negative potential, in particular via the connection unit, preferably up to -4 kV to -0.5 kV, at least temporarily more negative than the electrode emitter and / or the third electrode. The first electrode may in particular be in the shape of a disk, preferably an annular disk, having a first passage for electrons to pass through.

[0010] The second electrode may be a focusing electrode, and the focusing electrode may be at a positive potential during operation, in particular via the connection unit, relative to the first electrode and / or the third electrode and / or the electron emitter. The second electrode may be at ground potential during operation. The second electrode may in particular be in the shape of a disk, preferably an annular disk, having a second passage for electrons to pass through and / or to escape from the electron gun and / or the electron gun device. Thus, the second passage may at least partially define an opening of the electron gun and / or the electron gun device.

[0011] The insulator encompasses an open interior, and the axial direction is defined in particular by the normal on the surface of the open interior. Preferably, the insulator is annular. Preferably, the normal on the first insulator contact surface and / or the second insulator contact surface forms an angle of less than 60°, in particular less than 30°, preferably less than 15°, and ideally 0° with the axial direction. Advantageously, the axial direction is perpendicular to the first insulator contact surface and / or the second insulator contact surface. The first insulator contact surface and the second insulator contact surface are preferably parallel to each other.

[0012] The electron gun device may include another annular, preferably circular ceramic insulator having a different axial direction between the first electrode and the third electrode. The other insulator is fixed between the first electrode and the third electrode in the same manner as the insulator is fixed between the first electrode and the second electrode. For this purpose, the third electrode preferably has a third electrode contact surface facing the third insulator contact surface of the other insulator in the assembled state, and a third brazing joint joins the third electrode contact surface and the third insulator contact surface. The other insulator preferably further has a fourth insulator contact surface facing the fourth electrode contact surface of the first electrode, and a fourth brazing joint joins the fourth electrode contact surface and the fourth insulator contact surface in the assembled state. Preferably, the other insulator is at least mostly, preferably completely identical to the insulator. However, the other insulator may have a different total extension along its other axial direction than the insulator along its axial direction. Furthermore, the other insulator may have a different maximum and / or minimum lateral width with respect to its other axial direction than the insulator with respect to its axial direction.

[0013] The first electrode, the insulator, and the second electrode are stacked particularly vertically, with the first brazed joint and the second brazed joint interposed therebetween. The first electrode, the insulator, and the second electrode are stacked particularly facing each other, with the first brazed joint and the second brazed joint interposed therebetween. Preferably, the third electrode, another insulator, the first electrode, the insulator, and the second electrode are stacked vertically in a given order, particularly having brazed joints between each insulator-electrode pair. Preferably, the third electrode, another insulator, the first electrode, the insulator, and the second electrode are stacked facing each other in a given order, particularly having brazed joints between each insulator-electrode pair.

[0014] In the assembled state, the first electrode contact surface and the first insulator contact surface are preferably parallel to each other. In the assembled state, the second electrode contact surface and the second insulator contact surface are preferably parallel to each other. Preferably, the same applies to each contact surface between the first electrode, another insulator, and the third electrode. In the assembled state, the first electrode contact surface and the second electrode contact surface are preferably perpendicular to the third electrode contact surface, preferably also perpendicular to the fourth electrode contact surface, preferably with respect to the axial direction. Preferably, in the assembled state, the axial direction and another axial direction are parallel to each other. In the assembled state, the first passage, the second passage, and the open interior of the insulator are preferably aligned with another open interior of another insulator, particularly also aligned with the electrode emitter.

[0015] In particular, depending on the application field, the electron gun device can have four or more electrodes and can also have three or more insulators. The outer diameter of the first electrode and / or the second electrode and / or the third electrode is at least 5 mm and at most 20 mm. The thickness along the axial direction of the first electrode and / or the second electrode is preferably 0.1 mm to 0.5 mm.

[0016] A brazed joint is, in particular, an element that is arranged between respective contact surfaces and connects the respective contact surfaces, and these elements are formed by a brazing filler metal that solidifies after the brazing operation, in particular a brazing alloy. The brazed joint may at least partially, preferably completely, surround the open interior of an insulator and / or another open interior of another insulator. The brazed joint is preferably annular, in particular circular. Ideally, the brazed joint forms a continuous ring.

[0017] In this specification, the terms "parallel" or "perpendicular" are to be understood as having a maximum deviation of + / - 5° and / or as parallel or perpendicular taking into account manufacturing tolerances and / or installation tolerances. Further, the terms "first", "second", and "third" are to be understood merely as identifiers for distinguishing different elements from one another. They are not to be construed as suggesting an order and / or hierarchy of the elements. Further, the presence of a "second" element does not mean that a "first" element is present. Correspondingly, a reference to a "third" element does not mean that a "first" element and a "second" element must necessarily be present. The same applies to the term "further". A "further element" does not mean that a certain "element" is also present.

[0018] Furthermore, it is proposed that the first insulator contact surface and / or the second insulator contact surface and / or the third insulator contact surface and / or the fourth insulator contact surface include non-metallized portions, and preferably are essentially not metallized at all before brazing. Thereby, costs and / or assembly labor can be most advantageously reduced. Preferably, the insulator and / or another insulator is made entirely of a ceramic material. In an alternative embodiment, the first insulator contact surface and / or the second insulator contact surface and / or the third insulator contact surface and / or the fourth insulator contact surface can also include metallized portions and can be completely metallized before brazing.

[0019] Furthermore, it is proposed that the insulator and / or another insulator contain, preferably be made of, aluminum oxide or aluminum nitride, which can obtain advantageous material properties, particularly with respect to thermal properties such as thermal conductivity. By using aluminum nitride for the insulator and / or another insulator, the thermal performance can be further improved, and an excellent thermal conductivity benefit can be obtained compared to other insulator materials such as glass and aluminum oxide.

[0020] The first electrode and / or the second electrode and / or the third electrode can contain, preferably be made of, various materials such as tungsten, rhenium, and their alloys.

[0021] However, in a preferred embodiment of the present invention, it is proposed that the first electrode and / or the second electrode and / or the third electrode contain, preferably be made of, molybdenum or its alloy. Thus, during brazing and / or operation of the electron gun device, low thermal expansion of the electrodes can be obtained, which can particularly help the stability of the electron flow and the X-ray focus during operation. The combination of molybdenum for the electrodes and aluminum nitride for the insulator and / or another insulator is most advantageous because their thermal expansion coefficients are very similar, i.e., at 20°, molybdenum is 4.8 ppm / K and aluminum nitride is 4.0 - 5.0 ppm / K, and these can help balance the thermomechanical stresses accumulated during brazing. Combinations of other materials may cause stress cracks in the ceramic during brazing.

[0022] In particular, the use of active metal brazing is made possible by the planar geometry and / or material selection, reducing the need for prior metallization of the ceramic and significantly reducing the cost of the electron gun device. The active brazing works particularly well in this geometry when the parts are arranged forward because the molten active brazing metal shows relatively low wettability and does not flow well on the ceramic surface.

[0023] Therefore, it is proposed that the first brazing joint and / or the second brazing joint and / or the third brazing joint and / or the fourth brazing joint are active brazing joints. Preferably, all brazing joints are active brazing joints. Thereby, the cost and / or the assembly labor can be advantageously reduced. The first brazing joint and / or the second brazing joint and / or the third brazing joint and / or the fourth brazing joint are particularly preferably simultaneously, and most preferably achieved by an active metal brazing process carried out simultaneously in the same brazing furnace. The brazing is preferably carried out using an active brazing alloy on an insulator contact surface that is not metallized. Preferably, the brazing is carried out via high-temperature vacuum furnace brazing. In active metal brazing, a metal, preferably titanium, is added to the brazing alloy in particular to improve the reaction and wettability with the ceramic substrate. For example, the addition of titanium to some brazing alloy compositions results in an increase in reactivity and an improvement in wetting behavior, and for this reason the ceramic substrate is wetted, in particular, by the formation of an intermetallic interfacial reaction product that can form a joint with the brazing alloy. The active brazing alloy may be based on a 72Ag-28Cu eutectic alloy to which 1 to 5 wt% of titanium is added. Indium may be added to lower the eutectic temperature. However, other active brazing alloys, such as AgCuSnTi, are also conceivable.

[0024] In one embodiment of the present invention, the first brazed joint is performed using a first brazing foil between a first electrode contact surface and a first insulator contact surface, and / or the second brazed joint is performed using a second brazing foil between a second electrode contact surface and a second insulator contact surface, and / or the third brazed joint is performed using a third brazing foil between a third electrode contact surface and a third insulator contact surface, and / or the fourth brazed joint is proposed to be performed using a fourth brazing foil between a fourth electrode contact surface and a fourth insulator contact surface. Thereby, the assembly and / or manufacture of the electron gun device can be further simplified. The first brazing foil and / or the second brazing foil and / or the third brazing foil and / or the fourth brazing foil may be in the form of a ring, preferably an annular disk, most preferably a flat washer, and in the assembled state, may completely surround the open interior of the insulator and / or another open interior of another insulator. The thickness of the first brazing foil and / or the second brazing foil and / or the third brazing foil and / or the fourth brazing foil may be in the range of 0.025 mm to 0.050 mm. The brazing foil is made of an active metal brazing material, preferably AgCuSnTi. Preferably, all the brazing foils are identical to each other. During manufacture, the electrodes and one or more insulators may be stacked alternately with the brazing foils arranged alternately. The assembly is then heated in a brazing furnace, particularly a high-temperature vacuum furnace, thereby melting the brazing foil and enabling the entire assembly to be interconnected.

[0025] Advantageously, the insulator comprises at least one retaining mechanism for restricting the range of flow of the brazing filler metal during brazing. Thereby, a highly reliable and preferably easy brazing can be ensured. The retaining mechanism may include depressions and / or surface wrinkles for blocking the flow of the brazing filler metal. Correspondingly, another insulator may also be provided with at least one other retaining mechanism for restricting the range of flow of the brazing filler metal during brazing.

[0026] Preferably, the holding mechanism comprises a first collar that at least partially, preferably completely, surrounds the first insulator contact surface and / or a second collar that at least partially, preferably completely, surrounds the second insulator contact surface. Thereby, the range of the flow of the brazing filler metal can be advantageously restricted. Further, the first collar and / or the second collar can be used as a limiting stopper for another element, in particular the brazing foil. In particular, it is possible to ensure that the first brazing joint and / or the second brazing joint are located where they should be. The first collar and / or the second collar are preferably embodied as a part of the insulator lifted axially above the first contact surface and / or the second contact surface. Correspondingly, another holding mechanism of another insulator may comprise another first collar that at least partially, preferably completely, surrounds the third insulator contact surface and / or another second collar that at least partially, preferably completely, surrounds the fourth insulator contact surface.

[0027] In one embodiment of the invention, it is proposed that the holding mechanism and / or another holding mechanism further aim to position the brazing foil, in particular the first brazing foil and / or the second brazing foil described above, before brazing. Thus, the assembly and / or manufacture of the electron gun device can be further simplified, especially when no other fixing mechanism is used. Preferably, the first brazing foil and / or the second brazing foil fit exactly within the area surrounded by the first collar and / or the second collar, most preferably to prevent movement of the first brazing foil and / or the second brazing foil during handling of the pre-brazing assembly. Preferably, the third brazing foil and / or the fourth brazing foil fit exactly within the area surrounded by another first collar and / or another second collar, most preferably to prevent movement of the third brazing foil and / or the fourth brazing foil during handling of the pre-brazing assembly.

[0028] It is further proposed that the retaining mechanism preferably at least partially overlaps with the first electrode and / or the second electrode, at least with respect to the axial direction. The first color preferably covers the edge of the first electrode, and the second color preferably covers the edge of the second electrode. The first color and / or the second color may have an extension along the axial direction that is less than half of the thickness of the first electrode and / or the second electrode. The radial thickness of the first color and / or the second color may be on the order of a few tenths of a millimeter. Thereby, advantageous mechanical and / or electrical properties can be achieved. The retaining mechanism is preferably intended to function as a dielectric barrier against spurious electron emission near the electrode-insulator interface. Thereby, the reliability of the electron gun device can be enhanced.

[0029] In summary, the insulator and / or another insulator can be shaped to function as a guide for the brazing filler metal and a brazing fixture for the brazing foil, hold the brazing in place by foam lock, and prevent the active metal brazing from adhering to potential brazing fixtures. At the same time, this proposed shape of the insulator and / or another insulator can function both as a mechanical shield and an electric field former facing the outside of the X-ray tube.

[0030] Furthermore, a method for assembling an electron gun device, particularly the electron gun device described above, is proposed, wherein the electron gun device comprises a first metal electrode having a first electrode contact surface, a second metal electrode having a second electrode contact surface, and an annular ceramic insulator having a first insulator contact surface on a first side with respect to the axial direction of the insulator and a second insulator contact surface on a second side opposite to the axial direction. The first insulator contact surface is mounted facing the first electrode contact surface and connected to the first electrode contact surface via a first brazing. The second insulator contact surface is mounted facing the second electrode contact surface and connected to the second electrode contact surface via a second brazing, preferably performed simultaneously with the first brazing.

[0031] This enables the provision of an improved electron gun device. Costs can be reduced and the assembly parts can be simplified. The electron gun device obtained by the method according to the present invention is mechanically rigid and exhibits good thermal and electrical performance and stability.

[0032] It is further proposed that brazing be performed using an active brazing filler metal on an unmetallized insulator contact surface, thereby advantageously reducing costs and / or assembly labor as described above.

[0033] Preferably, the first brazing is performed using a first brazing foil between the first electrode contact surface and the first insulator contact surface, and / or the second brazing is performed using a second brazing foil between the second electrode contact surface and the second insulator contact surface, and / or the third brazing joint is performed using a third brazing foil between the third electrode contact surface and the third insulator contact surface, and / or the fourth brazing joint is performed using a fourth brazing foil between the fourth electrode contact surface and the fourth insulator contact surface. Thereby, the assembly and / or manufacture of the electron gun device can be further simplified. The flow of the brazing alloy can preferably be weakened by at least one holding mechanism that at least partially holds the brazing alloy between the contact surfaces during brazing.

[0034] It is understood that the subject matter of the present invention is not limited to the above-described embodiments. The described embodiments and features can be arbitrarily combined by those skilled in the art without departing from the subject matter of the present invention.

[0035] Preferred embodiments of the present invention will be described in more detail below with reference to the following attached schematic diagrams.

Brief Description of the Drawings

[0036]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0037] FIG. 1 shows an X-ray tube 12 whose geometric shape and operating mode are mostly known. The X-ray tube 12 includes an electron gun device 10. The X-ray tube 12 further includes an electron tube 50 in which the electron gun device 10 is at least partially disposed. At least during operation, the electron tube 50 is removed. The X-ray tube 12 includes a high-voltage source 48 for supplying a high voltage to the electron gun device 10 via a voltage source connection 60 of the X-ray tube 12. The electron gun device 10 is intended to generate free electrons 56 along an electron beam direction 62 and discharge them into the electron tube 50. The electrons 56 are accelerated toward a target head 52 of the X-ray tube 12 via the high voltage provided by the high-voltage source 48. The target head 52 includes a target 46, and the electrons 56 are directed thereto. When hitting the target 46, X-rays 58 are generated and can exit the target head 52 through a window 54 of the target head 52. The target 46 can be made of any suitable material, for example, tungsten.

[0038] The present invention is directed to the electron gun device 10 shown in an assembled state in FIG. 2. The electron gun device 10 includes an electron emitter 64 for generating free electrons 56. The electrode emitter 64 is an oxide-coated dispenser cathode, which is made from a porous tungsten block impregnated with a chemical substance, most importantly BaO (barium oxide), and its actual emitter surface is indirectly heated by a heating filament (not shown) potted with alumina. However, any other type of electron emitter is also conceivable.

[0039] Subsequently, the freed electrons 56 are accelerated and discharged through a stack of three metal electrodes 14, 18, 44, namely a first metal electrode 14, a second metal electrode 18, and a third metal electrode 44. In alternative embodiments, different numbers, such as two or at least four metal electrodes 14, 18, 44, can also be selected.

[0040] The electron emitter 64 is electrically connected to the third electrode 44. During operation, both the third electrode 44 and the electrode emitter 64 typically constitute a cathode with a potential of -3 kV to -0.5 kV. However, different potentials are also possible. The third electrode 44 is in the shape of a circular disk having recesses and / or notches for the electron emitter 64 and / or the conductor to the electron emitter 64 and / or the conductor for the high voltage source of the electrodes 14, 18, 44.

[0041] The first electrode 14 is disposed between the third electrode 44 and the second electrode 18. The first electrode 14 is a grid electrode for the purpose of controlling the electron beam. The potential of the first electrode 14 can be changed and can also be set to a potential negative with respect to the cathode potential. The first electrode 14 is in the shape of an annular disk having a first passage 66 for allowing electrons 56 to pass through. The first electrode 14 has a thickness of 0.1 mm to 0.5 mm.

[0042] The second electrode 18 is a focusing electrode. During operation, the second electrode 18 is at a potential more positive than the first electrode 14 and the third electrode 44. The second electrode 18 is at ground potential during operation. The second electrode 18 is in the shape of an annular disk having a second passage 68 for allowing electrons 56 to pass along the electron beam direction 62 and escape from the electron gun device 10. Thus, the second passage 68 defines the opening of the electron gun device 10. The second electrode 18 has a thickness of 0.1 mm to 0.5 mm.

[0043] The electron gun device 10 includes an annular ceramic insulator 22 and another annular ceramic insulator 23. The electrodes 14, 18, 44 are separated from each other and electrically insulated by the insulator 22 and the other insulator 23. FIG. 4 shows a top view of the insulator 22. The other insulator 23 is the same as the insulator 22 in this embodiment. However, the other insulator 23 can also have a different geometric shape and / or material composition from the insulator 22. The insulator 22 has an open interior 70. The other insulator 23 has another open interior 72. The open interiors 70, 72, the passages 66, 68, and the electron emitter 64 are all aligned along the axial direction 26 of the insulator 22 to allow electrons 56 to pass through. The open interiors 70, 72, the passages 66, 68, and the electron emitter 64 are all aligned along the electron beam direction 62.

[0044] The electrodes 14, 18, 44 and the insulators 22, 23 are stacked alternately up and down. The electrodes 14, 18, 44 and the insulators 22, 23 are stacked alternately forward. The order is, in order from the electron emitter 64, the third electrode 44, the other insulator 23, the first electrode 14, the insulator 22, and finally the second electrode 18. The distance along the axial direction 26 between the first electrode 14 and the second electrode 18 is 0.05 mm to 0.5 mm, particularly 0.25 mm. The distance along the axial direction 26 between the electron emitter 64 and the first electrode 14 is 0.05 mm to 0.5 mm, particularly 0.1 mm.

[0045] The first electrode 14 includes a first electrode contact surface 16. The second electrode 18 has a second electrode contact surface 20. The insulator 22 has a first insulator contact surface 24 on a first side with respect to the axial direction 26 parallel to the electron beam direction 62 and a second insulator contact surface 28 on a second side opposite to the axial direction 26. In the assembled state, the first insulator contact surface 24 faces the first electrode contact surface 16 and is connected to the first electrode contact surface 16 via a first brazed joint 30. Similarly, the second insulator contact surface 28 faces the second electrode contact surface 20 and is connected to the second electrode contact surface 20 via a second brazed joint 32.

[0046] The electrodes 14, 18, and 44 are made of molybdenum. The insulators 22 and 23 are made of any typical industrial ceramic such as aluminum oxide or aluminum nitride, and aluminum nitride is preferred because it has a thermal expansion coefficient similar to that of molybdenum. Each of the insulators 22 and 23 is connected to two of the electrodes 14, 18, and 44 by active metal brazing in a high-temperature vacuum furnace (not shown). The first insulator contact surface 24 and the second insulator contact surface 28 are essentially not metallized at all before brazing. The first brazed joint 30 and the second brazed joint 32 are active brazed joints.

[0047] Figure 3 shows an exploded view of the electron gun device 10 before brazing. The first brazed joint 30 is made using a first brazing foil 34 between the first electrode contact surface 16 and the first insulator contact surface 24, and the second brazed joint 32 is made using a second brazing foil 36 between the second electrode contact surface 20 and the second insulator contact surface 28. The brazing foils 34 and 36 are made of an active metal brazing material. Figure 5 shows a top view of the first brazing foil 34. The second brazing foil 36 is the same as the first brazing foil 34 of the present embodiment. However, the second brazing foil 36 can also have a different geometric shape and / or material composition from the first brazing foil 34.

[0048] The insulator 22 includes a holding mechanism 38 for restricting the range of flow of the brazing filler metal during brazing. The holding mechanism 38 is further intended to position the first brazing foil 34 and the second brazing foil 36 before brazing. The holding mechanism 38 includes a first collar 40 that completely surrounds the first insulator contact surface 24 and a second collar 74 that completely surrounds the second insulator contact surface 28. The brazing foils 34 and 36 are sized to fit snugly into their respective collars 40 and 74 and not reach the open interior 70 of the insulator 22. The cross-sectional areas of the insulators 22 and 23 are those of a vertically compressed letter "T" in which the collars 40 and 74 form at least part of the crossbar.

[0049] In the assembled state, the retaining mechanism 38 and the colors 40, 74 overlap at least partially with the first electrode 14 and the second electrode 18 with respect to the axial direction 26. During operation, the retaining mechanism 38 is intended to function as a dielectric barrier against spurious electron emission near the electrode-insulator interface 42.

[0050] The above description regarding the connection of the insulator 22 to the first electrode 14 and the second electrode 18 equally applies to the connection of another insulator 23 to the first electrode 14 and the third electrode 44.

[0051] Figure 6 is a flowchart of a method for assembling an electron gun device. In step 100, the electrodes 14, 18, 44, the insulators 22, 23 and the brazing foils 34, 36 are stacked as shown in Figure 3. In the next step 110, this assembly is brazed by active metal brazing in a high-temperature vacuum furnace (not shown). In the next step 120, the assembly is allowed to cool or actively cooled. In step 130, the electrode emitter 64 is attached to the third electrode 44. In step 140, all remaining electrical connections for connecting the first electrode 14 and the second electrode 18 are completed. In an alternative embodiment, step 130 and / or step 140 can also be performed first.

Description of Reference Numerals

[0052] 10 Electron gun device 12 X-ray tube 14 First electrode 16 First electrode contact surface 18 Second electrode 20 Second electrode contact surface 22 Insulator 23 Another insulator 24 First insulator contact surface 26 Axial direction 28 Second insulator contact surface 30 First brazed joint 32 Second brazed joint 34 First brazing foil 36 Second brazing foil 38 Holding mechanism 40 First color 42 Electrode-insulator interface 44 Third electrode 46 Target 48 High voltage source 50 Electron tube 52 Target head 54 Window 56 Electron 58 X-ray 60 Voltage source connection 62 Electron beam direction 64 Electron emitter 66 First passage 68 Second passage 70 Open interior 72 Another open interior 74 Second color 100 Step 110 Step 120 Step 130 Step 140 Step

Claims

1. An electron gun device (10), in particular for an X-ray tube (12), said electron gun device (10) comprising: a metallic first electrode (14) having a first electrode contact surface (16); a second electrode (18) made of metal having a second electrode contact surface (20); an annular ceramic insulator (22); Equipped with the annular ceramic insulator (22) has a first insulator contact surface (24) on a first side relative to an axial direction (26) of the insulator (22) and a second insulator contact surface (28) on a second opposite side relative to the axial direction (26); In an assembled state, the first insulator contact surface (24) faces the first electrode contact surface (16) and is connected to the first electrode contact surface (16) via a first brazed joint (30); the second insulator contact surface (28) faces the second electrode contact surface (20) and is connected to the second electrode contact surface (20) via a second brazed joint (32); An electron gun device (10).

2. the first brazed joint (30) and / or the second brazed joint (32) are active brazed joints; 2. The electron gun apparatus (10) of claim 1.

3. the first insulator contact surface (24) and / or the second insulator contact surface (28) include a non-metallized portion, and preferably are essentially completely free of metallization prior to brazing; Electron gun apparatus (10) according to claim 1 or 2.

4. the first brazing joint (30) is performed using a first brazing foil (34) between the first electrode contact surface (16) and the first insulator contact surface (24); and / or The second brazing joint (32) is performed using a second brazing foil (36) between the second electrode contact surface (20) and the second insulator contact surface (28). Electron gun apparatus (10) according to any one of claims 1 to 3.

5. the first electrode (14) and / or the second electrode (18) contain, and are preferably made of, molybdenum or an alloy thereof; Electron gun apparatus (10) according to any one of claims 1 to 4.

6. The insulator (22) contains aluminum oxide or aluminum nitride, and is preferably made of aluminum oxide or aluminum nitride. Electron gun apparatus (10) according to any one of the preceding claims.

7. The insulator (22) includes at least one retention feature (38) for limiting the extent of flow of braze filler metal during brazing. Electron gun apparatus (10) according to any one of the preceding claims.

8. The retention mechanism (38) is further intended to position the brazing foils (34, 36) prior to brazing.

8. An electron gun apparatus (10) according to claim 7.

9. the retention mechanism (38) comprises a first collar (40) at least partially, and preferably completely, surrounding the first insulator contact surface (24); and / or The retention mechanism (38) comprises a second collar (74) at least partially, and preferably completely, surrounding the second insulator contact surface (28).

9. An electron gun apparatus (10) according to claim 7 or 8.

10. the retention feature (38) preferably at least partially overlaps the first electrode (14) and / or the second electrode (18) at least in the axial direction (26); Electron gun apparatus (10) according to any one of claims 7 to 9.

11. The retention mechanism (38) is intended to act as a dielectric barrier against spurious electron emissions near the electrode-insulator interface (42). Electron gun apparatus (10) according to any one of the preceding claims.

12. An X-ray tube (12) comprising an electron gun device (10) according to any one of claims 1 to 11.

13. A method for assembling an electron gun arrangement (10), in particular for an X-ray tube (12), in accordance with any one of claims 1 to 11, said electron gun arrangement (10) comprising: a metallic first electrode (14) having a first electrode contact surface (16); a second electrode (18) made of metal having a second electrode contact surface (20); an annular ceramic insulator (22); Equipped with the annular ceramic insulator has a first insulator contact surface (24) on a first side relative to an axial direction (26) of the insulator (22) and a second insulator contact surface (28) on a second opposite side relative to the axial direction (26); the first insulator contact surface (24) is mounted facing the first electrode contact surface (16) and connected to the first electrode contact surface (16) via a first braze; the second insulator contact surface (28) is mounted facing the second electrode contact surface (20) and is connected to the second electrode contact surface (20) via a second brazing, preferably performed simultaneously with the first brazing; method.

14. The brazing is performed using an active braze filler metal on the non-metallized insulator contact surfaces (24, 28); The method of claim 13.

15. the first brazing is performed using a first brazing foil (34) between the first electrode contact surface (16) and the first insulator contact surface (24); and / or The second brazing is performed using a second brazing foil (36) between the second electrode contact surface (20) and the second insulator contact surface (28).

15. The method according to claim 13 or 14.

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