Electron emitter of rotating tube shell X-ray tube, rotating tube shell X-ray tube and rotating tube shell X-ray radiator

Abstract

The invention relates to an electron emitter, a rotating tube shell X-ray tube and a rotating tube shell X-ray radiator. The invention relates to an electron emitter for a rotating housing X-ray tube, comprising: a segmented emitter surface, the segmented emitter surface having at least two emitter elements that can be activated independently of one another; the at least two emitter elements are arranged in such a way that the segmented emitter surfaces are formed in an axially symmetrical manner in the plane of the emitter surfaces, and are configured to activate at least a subset of the segments of the segmented emitter surfaces as activated emitter surfaces for emission of electrons from the activated emitter surfaces, and the at least two emitter elements are arranged in such a way that the segmented emitter surfaces are formed in an axially symmetrical manner in the plane of the emitter surfaces. Wherein at least one of the at least two emitter elements is designed for thermionic emission of electrons, characterized in that the at least two emitter elements are arranged close to each other such that the distance between the respective emitter surfaces is minimized.

Description

Technical Field

[0001] The invention relates to an electron emitter, a rotating tube shell X-ray tube and a rotating tube shell X-ray radiator. Background Art

[0002] Conventional rotating envelope X-ray radiators typically comprise a housing and a rotating envelope X-ray tube, which is supported in the housing so as to be rotatable relative to the housing. For example, DE 19 741 750 A1 discloses such an X-ray radiator, which has a forced-cooled rotating anode and has a rotating envelope tube, the vacuum jacket of which rotates in a radiator housing filled with a liquid coolant.

[0003] Thus, in conventional rotating envelope X-ray radiators, typically the entire rotating envelope X-ray tube, in particular the evacuated rotating envelope, rotates together with the anode. In some rotating envelope X-ray radiators, the cathode with the electron emitter is also connected to the rotating envelope in a rotationally fixed manner, so that the cathode, the anode and the rotating envelope have the same rotational frequency. Other rotating envelope X-ray radiators have a cathode with an electron emitter, which is fixed in position and does not rotate together with the anode and the rotating envelope, as described, for example, in DE 4 108 591 A1. In contrast, in conventional rotating anode X-ray tubes, only the rotating anode rotates relative to the evacuated tube housing.

[0004] Another difference between conventional rotating anode X-ray tubes and conventional rotating envelope X-ray tubes relates to the placement of the electron emitters. In conventional rotating anode X-ray tubes, the electron emitter, which is fixed in position opposite to the anode, is usually placed eccentrically outside the axis of rotation directly on the circular focal track of the anode. The focal track is generated in particular in that the electrons that reach the focal spot interact with the anode on the circular track due to the rotation of the anode. The electron emitter of such a rotating anode X-ray tube can have, for example, up to three different emitter elements, the emitted electrons of which can be geometrically focused on different focal spot sizes. The focusing is achieved in particular by means of a deflection unit, which generates an electric field or an electromagnetic field for this purpose.

[0005] In conventional rotating envelope X-ray tubes, the electron emitter is typically located centrally above the anode on the axis of rotation. In order to keep the focal spot fixed in position relative to the housing, the emitted electrons are usually deflected from the axis of rotation to the edge region of the anode by means of an electromagnetic field. For this purpose, the deflection unit has, in particular, a first quadrupole magnet, which is configured to set the ratio of the length and width of the focal spot. If the deflection unit has a second quadrupole magnet, the size of the focal spot can typically be set with the second quadrupole magnet. The design of a rotating envelope X-ray radiator with at least one quadrupole magnet is relatively complex and cost-intensive.

[0006] Furthermore, it is known to deflect the emitted electrons at a correspondingly high frequency so that they jump back and forth on the anode, thereby effectively enlarging the focal spot. Alternatively or additionally, it is possible to deform the focal spot by means of a variable grid voltage applied between the electron emitter and the focusing cylinder. Summary of the invention

[0007] The object underlying the present invention is to specify an electron emitter, a rotating tube x-ray tube and a rotating tube x-ray radiator having a simpler and thus more cost-effective construction.

[0008] This object is achieved by the features of the independent claim. Advantageous embodiments are described in the dependent claims.

[0010] The electron emitter for a rotating tube-shell X-ray tube according to the present invention has:

[0011] a segmented emitter surface, wherein the segmented emitter surface has at least two emitter elements which can be activated independently of one another, and configuration for activating at least a subset of the segments of the segmented emitter surface as an activated emission surface for emitting electrons from the activated emission surface, wherein the at least two emitter elements are arranged such that the segmented emitter surface is designed axisymmetrically in the emitter surface plane,

[0012] wherein at least one emitter element of the at least two emitter elements is configured for thermionic emission of electrons,

[0013] It is characterized in that

[0014] At least two transmitter elements are arranged close to one another in such a way that the distance between the respective transmitter surfaces is minimal.

[0015] By arranging a plurality of emitter elements as close to one another as possible, the size of the focal spot can advantageously be varied cost-effectively in relation to the extent of the active emission surface. In this case, preferably, a deflection unit, which usually requires relatively expensive quadrupole magnets, can be designed less complex, in particular without quadrupole magnets, and thus more cost-effectively. The invention achieves a further advantage in that the field effect can in principle be used—in combination with thermionic emitter elements or using only thermionic emitter elements. Due to its cost advantage, it is particularly advantageous to use emitter elements for thermionic emission.

[0016] The electron emitter is particularly suitable for medical imaging. Alternatively or additionally, the electron emitter may be suitable for material inspection.

[0017] The emitter face of an electron emitter usually has at least as many segments as emitter elements which are part of the electron emitter. Thus, an electron emitter typically has at least two segments.

[0018] Typically, one segment corresponds to each emitter surface. It is conceivable that, depending on the design of the emitter element and / or the emitter surface, the emitter surface comprises more than one segment. In this case, for example, the emitter surface can be divided into sub-areas that can be activated independently of one another. Thus, it is conceivable in principle that an electron emitter having two electron emitters has an emitter surface with more than two segments.

[0019] The activatable emitter element is particularly designed so that the electron emission can be switched on or off via the activated emission surface of the emitter element. In the latter case, this means that the emitter element does not have an activated emission surface, but a deactivated emission surface. The activation or deactivation of the emission surface can be carried out in a clocked manner and / or multiple times according to an emitter switching signal. The emitter switching signal can be provided in particular by a control unit. The emitter switching signal can include, for example, switching on or off a thermionic heating current device connected upstream of the emitter element, switching on or off a high voltage at a gate connected downstream of the emitter element and / or switching on or off a gate voltage of the emitter element.

[0020] The segmented transmitter surface being configured for activating at least a subset of the segments means, in particular, that the segmented transmitter surface is or can be at least partially activated, for example, as a function of a transmitter switching signal. For example, the transmitter switching signal can contain an indication of the segments to be activated or activated that form the subset and / or directly activate the segments based on an electrical and / or physical connection.

[0021] If a transmitter element has more than one segment, the activated emission surface of the transmitter element may comprise only the activated segment. Alternatively, it is conceivable that the activated emission surface comprises at least one deactivated segment.

[0022] Axisymmetry in the emitter surface plane means in particular that the electron emitter comprises at least one axis of symmetry. Depending on the design of the electron emitter, the axis of symmetry can be located within one emitter element or within a plurality of emitter elements. Alternatively or additionally, the axis of symmetry can be located between two adjacent emitter elements.

[0023] The emission of electrons can typically be distinguished according to the physical effect on which the emission is based. In the case of thermionic emission, in particular direct or indirect heating of the electron emitter is carried out, which emits electrons after reaching a minimum temperature. In the case of direct heating, in particular the electron emitter itself is heated by means of a heating current, which is provided, for example, by a heating current device. In the case of indirect heating, a further thermionic or non-thermic emitter element is connected upstream of the thermionic emitter element, which heats the thermionic emitter element together with the electrons emitted into a vacuum, in which the free electrons are accelerated from the electron emitter connected upstream towards the thermionic emitter. In this case, the heating current device is typically connected to the electron emitter connected upstream in order to provide the heating current.

[0024] Field effect emission is carried out in particular by applying a gate voltage to a carrier of the emitter element, on which a plurality of field effect emitter needles are arranged. Electrons are emitted by the applied gate voltage, in particular at the tips of the field effect emitter needles. The field effect emitter needles usually contain carbon, silicon and / or molybdenum.

[0025] In particular in field effect emitter elements and / or in indirectly heated thermionic emitter elements, the emitter surface of such an emitter element may have a plurality of segments. The activation of only some, i.e. not all, of such an emitter element may take place, for example, in that only some of the emitter needles are excited to emit with field effect or only certain regions of the indirectly heated electron emitter are heated with free electrons.

[0026] The emitter elements are preferably arranged as close to one another as possible. The spacing between the respective emitter surfaces is advantageously small, so that the emitter surfaces merge approximately into one another. Typically, there is a galvanic isolation between the emitter surfaces in any case. At least two emitter elements are arranged in particular close to one another so that in the case of simultaneous emission of electrons, the emitted electrons can be directly superimposed and / or cannot be distinguished. The emitter surfaces of the emitter elements are typically arranged and oriented such that the segmented emitter surfaces lie in one plane and / or are flat.

[0027] In particular, the electron emitter can adopt different operating states over time. It is conceivable that the operating states are configured so that the corresponding emitter elements do not operate alternately. In other words, the activated emission surface does not change from one electron emitter to another electron emitter over time. When an emitter element is additionally activated or deactivated, the activated emission surface generally changes only in its extension. In the example with a total of two electron emitters, this means that in theory a total of four operating states can conventionally be conceived, namely no emitter element is activated, one emitter element is activated, and two emitter elements are activated. Preferably, the electron emitter according to the invention is limited to three operating states, namely no emitter element is activated, one emitter element is activated, and two emitter elements are activated.

[0028] One embodiment proposes that the segmented emitter surface is composed of two emitter elements and is essentially rotationally symmetrical, wherein the first emitter element is annularly formed with a central opening, and wherein the second emitter element is arranged in the first emitter element in the central opening. This embodiment is particularly advantageous because the first emitter element realizes a rotationally symmetrical electron emitter due to the annular shape, which is particularly advantageous for a rotating tube shell X-ray tube. This embodiment advantageously realizes two different extensions at the activated emission surface and thus two focal spot sizes. Essentially rotationally symmetrical means that the first emitter element describes a complete ring and / or circle, except for usually two conveying parts to the first emitter element, which may be necessary for heating and / or maintaining the electron emitter. The emitter surface of the first emitter element and the emitter surface of the second emitter element are typically located in the emitter surface plane. The first emitter element is especially bent around the central opening. The central opening especially realizes that the second emitter element is arranged in this central opening.

[0029] In particular, the first emitter element can be a spiral emitter and thus be designed for thermionic emission of electrons. Alternatively or additionally, the second emitter element can be designed for thermionic emission, for example as a spiral emitter or a surface emitter. The second emitter element can alternatively be designed as a field effect emitter element. This embodiment offers the advantage that the spiral emitter can be designed particularly simply in an annular shape.

[0030] One embodiment proposes that the segmented emitter surface is composed of two emitter elements, which are axially symmetrical and rectangular about two spatial axes perpendicular to each other, and the height of the segmented emitter surface is greater than the width. Therefore, the electron emitter has a total of two emitter elements that can be activated independently of each other. The corresponding emitter surfaces of the two electron emitters can be rectangular, especially square. In the embodiment, the electron emitter includes two axes of symmetry, which are perpendicular to each other. One of the two axes of symmetry is especially located on a dividing line between the two emitter elements, wherein the width of the dividing line is predetermined by the spacing between the two emitter elements. The other of the two axes of symmetry extends, especially centrally, through the two emitter elements. The segmented emitter surface is not square in particular. In other words, the height of the extension of the emitter surface is greater than the width or the width is greater than the height, depending on the viewing angle of the emitter surface. The embodiment realizes an electron emitter with slightly asymmetrically mounted emitter elements and two focal spot sizes.

[0031] In particular, the first emitter element can be a spiral emitter and the second emitter element can be a spiral emitter. Said embodiment enables a relatively cost-effective electron emitter.

[0032] One embodiment proposes that the segmented emitter surface is composed of three emitter elements arranged side by side on a straight line and has a height greater than the width, and the emitter surface of one of the emitter elements is larger than the emitter surface of the other two emitter elements added together. The straight line can especially correspond to the axis of symmetry. The emitter elements are especially arranged in a row on the straight line. Preferably, the spacing between each two adjacent emitter elements is minimal. The segmented emitter surface is especially rectangular, non-square and / or has a width greater than the height. The relatively large emitter surface is typically arranged between the two small emitter surfaces. In one operating state, for example, all three emitter elements can be operated, and in another operating state, for example, only the emitter element with the relatively large emitter surface can be operated.

[0033] In particular, each emitter element can be a spiral emitter and / or a surface emitter. Alternatively, the central emitter element can be a spiral emitter and / or a surface emitter, and the emitter elements adjacent to the central emitter element are non-spiral line emitters. A non-spiral line emitter is in particular a thermionic emitter consisting of a single line. The line emitter can in particular be straight. If the line emitter is curved, the number of turns is then usually less than 2, preferably less than 1. The spiral emitter has a number of turns of at least 2.

[0034] One embodiment provides that two adjacent transmitter elements are oriented relative to one another in such a way that the transmitter longitudinal directions are perpendicular to one another. In spiral transmitters, the transmitter longitudinal direction is defined in particular as the direction in which the windings are arranged one behind the other. In line transmitters, the transmitter longitudinal direction is defined as the direction of the longest extension of the line.

[0035] The rotating tube housing X-ray tube according to the present invention has:

[0036] -cathode,

[0037] - a rotating housing which can be evacuated and which can be supported at a rotational frequency about a rotation axis relative to a fixed support element, and

[0038] -anode,

[0039] The cathode and the anode are connected to the rotating shell in a rotationally fixed manner.

[0040] The cathode comprises a cathode head and an electron emitter which is inserted into the cathode head in a rotationally fixed manner.

[0041] It is characterized in that the rotating bulb is made of glass in the section between the anode and the cathode.

[0042] The rotating envelope as a glass embodiment offers in particular advantages resulting directly from the outer shape of the rotating envelope and thus the rotating envelope X-ray tube. The rotating envelope X-ray tube according to the invention is particularly suitable as a relatively cost-effective embodiment.

[0043] Another advantage of the rotating bulb is that the glass is insulating, so that the optional deflection unit can be positioned closer to the glass bulb. The insulating properties of glass are also particularly advantageous, since no other materials, such as conventional ceramics, need to be used for electrical insulation.

[0044] The rotating envelope according to the invention as a glass embodiment can be referred to in particular as a glass bulb. The glass bulb advantageously enables a relatively compact construction which, in contrast to conventional rotating envelope X-ray radiators, does not require a waist. The minimum length of the rotating envelope is therefore predetermined in particular by the required insulation length between the anode and the cathode. Thus, the deflection of the emitted electrons by means of the deflection unit can preferably take place directly from the cathode, whereas in conventional rotating envelope X-ray radiators the deflection takes place after the waist.

[0045] In rotating envelope X-ray tubes, the cooling of the anode is direct cooling, wherein the heat can be discharged from the anode directly into a cooling medium, for example oil, which flows around the rotating envelope. Thus, temporary storage of heat in an intermediate heat reservoir, which is thermally coupled to the anode and usually consists of graphite, can advantageously be omitted. Therefore, preferably, the maximum thermal load of the anode is relatively large in relation to the size of the anode and the heat capacity which is related to this size to a certain extent.

[0046] The rotating envelope X-ray tube, in particular the rotating envelope, is typically vacuum-capable. The rotating envelope is advantageously hermetically sealed. The evacuated rotating envelope in particular includes a high vacuum.

[0047] The rotating housing can be supported or supported about the rotation axis, in particular by means of a support mechanism. The rotating housing can be rotated about the rotation axis, in particular at a rotation frequency. The fixed support part can in particular be part of the support unit. The fixed support part is in particular part of the rotating housing X-ray radiator and is not part of the rotating housing X-ray tube. In principle, it is conceivable that the support unit as a whole and thus the fixed support part are part of the rotating housing X-ray tube.

[0048] The cathode head can alternatively have in particular a support mechanism, wherein the cathode head can be supported around the axis of rotation by means of the support mechanism. The cathode head can in particular be supported with respect to a fixed support part. The fixed support part and optionally the support mechanism can be part of a support unit. The support unit can in particular be a part of a rotating support and / or a cathode or a part of a rotating tube housing X-ray tube or a part of a rotating tube housing X-ray radiator. The support mechanism can be, for example, a rotor and / or a rotating support part. The fixed support part can in particular be a stator. The rotating support can in particular be a ball bearing or in particular a liquid metal bearing, a sliding bearing.

[0049] The support unit enables in particular the cathode head or the electron emitter or the rotating bulb to be rotated at a rotational frequency, which is, for example, at least 5 Hz, in particular 50 Hz, preferably 200 Hz.

[0050] The cathode and the anode are usually arranged on opposite sides in the rotating tube shell. In particular, a high vacuum is present between the cathode and the anode. The rotationally fixed connection of the cathode and the anode to the rotating tube shell is realized, for example, by means of a fastening means. The fastening means can in particular be a soldering point and / or a welding point. The rotationally fixed connection of the cathode and the anode to the rotating tube shell can alternatively or additionally be realized by means of a component of the support unit, so that the cathode and the anode are not directly coupled to the rotating tube shell. The anode and the cathode as well as the electron emitter and the rotating tube shell rotate in particular together around the rotation axis at the same rotation frequency.

[0051] The section made of glass between the anode and the cathode is particularly formed in an annular shape and / or rotationally symmetrically with respect to the axis of rotation. The glass section particularly extends in the longitudinal direction of the rotating tube shell at least over half the distance between the cathode and the anode. The glass section can extend in the longitudinal direction of the rotating tube shell to the height of the cathode or beyond the height of the cathode. Alternatively or additionally, the glass section can extend in the longitudinal direction of the rotating tube shell to the height in front of the focal track on the anode or behind the focal track on the anode. In the latter case, the glass section is particularly used as an X-ray exit window. The focal track particularly includes the focal spot where the emitted electrons are projected onto the anode, and forms an annular focal track due to the rotation.

[0052] The cathode head usually has a circular outer shape and can be designed as a focusing head. The outer shape of the cathode head can alternatively be elliptical or polygonal.

[0053] The cathode head is supportable, which applies in particular to the electron emitter in a similar manner. In other words, the support means can be a part of the electron emitter, by means of which the electron emitter can be supported rotatably about the rotation axis at a rotation frequency relative to a fixed support component. In particular, since the electron emitter is inserted into the cathode head in a rotationally fixed manner, the support of the cathode head also means the support of the electron emitter, and vice versa.

[0054] The electron emitter is particularly suitable for medical imaging. Alternatively or additionally, the electron emitter may be suitable for material inspection.

[0055] The electron emitter is typically fixedly connected to the cathode head and thus to the rotating tube shell. The rotationally fixed insertion includes in particular rotationally fixed fastening. The electron emitter can be inserted into the cathode head in particular by means of fastening means. The fastening means can be screws, soldering points and / or welding points.

[0056] One embodiment provides that the rotating housing is cylindrical, and the first end side of the cylindrical rotating housing is configured to accommodate a cathode-side support part, and the second end side of the cylindrical rotating housing is configured to accommodate an anode-side support part, wherein the cathode is fastened to the cathode-side support part, and the anode is fastened to the anode-side support part, and wherein the cathode-side support part and the anode-side support part are configured to rotate the rotating housing relative to a fixed support part about a rotation axis. The cylindrical shape advantageously enables a compact rotating housing X-ray tube. The first end side and the second end side close the cylindrical rotating housing on opposite sides along the rotation axis. The center axis of the cylinder corresponds in particular to the rotation axis. The cathode-side support part can be connected to the rotating housing in a vacuum-tight manner, in particular at the first end side. The anode-side support part can be connected to the rotating housing in a vacuum-tight manner, in particular at the second end side. The cathode-side support part and / or the anode-side support part are typically part of a support unit, in particular a rotating support part and / or a rotor. The cathode-side support element and / or the anode-side support element can cooperate, in particular, with a fixed support element for the purpose of rotating the rotating bulb.

[0057] One embodiment proposes that the rotating shell is cylindrically configured and the entire side surface of the rotating shell is composed of glass. In this case, the rotating shell can be essentially composed of the side surface and / or only of glass. This embodiment is particularly advantageous compared to the previous embodiment.

[0058] One embodiment provides that the rotating tube housing X-ray tube is a bipolar high-voltage tube, wherein a negative high-voltage potential is applied to the cathode and a positive high-voltage potential is applied to the anode. The difference between the positive high-voltage potential and the negative high-voltage potential indicates in particular an acceleration voltage, according to which electrons can be accelerated from the cathode to the anode. Alternatively, it is conceivable that the cathode or the anode is at ground potential and only one of the two electrodes is at high-voltage potential.

[0059] One embodiment proposes that the diameter of the rotating tube shell perpendicular to the rotation axis is less than 100 mm, preferably 85 mm or 65 mm. In the embodiment, the center axis of the rotating tube shell corresponds in particular to the rotation axis. The rotating tube shell is especially constructed rotationally symmetrically with respect to the rotation axis. The structure is advantageous due to its compactness.

[0060] One embodiment provides that the length of the rotating tube shell along the rotation axis is less than 200 mm. In the embodiment, the center axis of the rotating tube shell corresponds in particular to the rotation axis. The rotating tube shell is in particular configured rotationally symmetrically with respect to the rotation axis. This advantageously allows the structure of the rotating tube shell X-ray tube to be smaller.

[0061] One embodiment provides that the rotating tube housing can rotate about the rotation axis by means of a ball bearing. In this case, the bearing unit is a rotating bearing, which is designed as a ball bearing. The bearing unit can be stored in oil or in a vacuum. The bearing means can in particular be balls of a ball bearing.

[0062] The rotating tube shell X-ray radiator according to the present invention has:

[0063] -case,

[0064] - Rotating tube X-ray tube, and

[0065] - deflection unit,

[0066] The rotating tube X-ray tube is supported in the housing so as to be rotatable about the rotation axis at a rotation frequency relative to the housing.

[0067] The rotating tube shell X-ray tube comprises a cathode, a rotating tube shell and an anode.

[0068] The anode is connected to the rotating shell in a rotationally fixed manner.

[0069] The cathode has a cathode head and an electron emitter inserted into the cathode head for emitting electrons, and is arranged on a rotating axis in a rotating tube shell.

[0070] It is characterized in that the deflection unit is configured to generate an inhomogeneous field between the cathode and the anode in a rotating tube shell, wherein the inhomogeneous field affects the emitted electrons to make them on different orbits towards the anode, and is designed to take into account the difference in path lengths of the emitted electrons along different orbits in the inhomogeneous field.

[0071] A rotating envelope X-ray radiator is particularly advantageous because, by using a deflection unit to generate the inhomogeneous field, the construction of the rotating envelope X-ray radiator is substantially less complex and thus more cost-effective. The rotating envelope X-ray radiator preferably does not comprise a separate dipole / quadrupole magnet or other additional multipole magnets. According to the invention, an inhomogeneous field is generated without using dipole / quadrupole magnets or other additional multipole magnets in order to deflect the electrons and simultaneously focus them in a suitable manner. Since the inhomogeneous field takes into account the path length differences of the emitted electrons, the necessity for a complex deflection is preferably eliminated. Advantageously, the deflection unit achieves a uniform distribution in the electrical focal spot, which distribution is preferably accompanied by a uniform temperature distribution.

[0072] The housing typically completely surrounds the rotating tube housing X-ray tube and the deflection unit and / or is closed. The housing can have a cooling medium for cooling the rotating tube housing X-ray tube and / or the deflection unit. The cooling medium can be liquid and / or gaseous. The cooling medium is in particular air and / or oil. The housing can have a cooling device, by which the cooling medium is tempered and / or replaced and / or circulated. The cooling device can have a heat exchanger and / or a cooling medium conveyor and a cooling medium discharge. On the outside of the housing, the surface of the housing can be enlarged, for example, by cooling fins.

[0073] The deflection unit generates an inhomogeneous field, in particular in a manner which conventionally requires a quadrupole magnet. According to the invention, the deflection unit is simplified compared to conventional rotating tube X-ray radiators with quadrupole magnets, whereby the deflection unit can be optimally set for relatively few operating points. In contrast, the deflection unit according to the invention is thus technically less complex, does not require complex adjustments and is therefore more cost-effective.

[0074] The deflection unit preferably generates the inhomogeneous field in such a way that the electrons can be fanned out and / or deflected in the radial direction, in particular taking into account the path length differences. The fanning out in the radial direction advantageously increases the length of the electric focal spot. The deflection in the radial direction in particular enables the electrons to reach a preset focal track. A further advantage of the radial deflection is that the width of the focal spot can be reduced, in particular when the activated emission surface of the electron emitter is wider than the desired optical width.

[0075] The deflection unit generates, in particular, a field whose field strength is position-dependent. The deflection unit generates, in particular, such an inhomogeneous field in a volume section of the rotating tube shell located between the electron emitter and the anode. The volume section is located, in particular, between the activated emission surface and the focal track on the anode. It is conceivable that the volume section is not located in a direct line of sight between the activated emission surface and the focal track, in particular due to forces acting on the electrons, which are obtained from the generated inhomogeneous field. The deflection unit is in particular arranged and oriented so that forces act on a large part of the emitted electrons, which are obtained from the generated inhomogeneous field. The deflection and / or fanning out of the electrons in the radial direction is mostly carried out, in particular, by means of position-dependent forces.

[0076] The deflection unit generating the inhomogeneous field can include generating a homogeneous field in another volume segment by means of the deflection unit. In principle, it is conceivable that in the volume segment with the inhomogeneous field, a small part of the field strength is independent of the position. The part is advantageously located outside the flight trajectory of the electrons and / or acts on less than 50%, preferably less than 20% of the emitted electrons. The deflection unit is particularly aligned with the trajectory of the electrons so that a large part, advantageously at least 80%, of the electrons are affected by the inhomogeneous field. The deflection unit is particularly aligned with the trajectory of the electrons so that a large part, advantageously at least 80%, of the electrons are affected by the inhomogeneous field.

[0077] The deflection unit generates an inhomogeneous field, which is static in an emission time period. The inhomogeneous field is constant in particular in an emission time period. The emission time period includes in particular at least one pulse duration of an X-ray pulse.

[0078] The influence on the emitted electrons on their different orbits means in particular that, due to the inhomogeneous field, a force acts on the emitted electrons, which force may cause a deflection of at least one electron. Since the electron emitter is usually not a point-like electron source, but emits electrons from an activated emission surface in a specific, non-point-like extension with different starting positions, the emitted electrons usually have a spatial distribution perpendicular to the axis of rotation, which causes the emitted electrons to propagate on different orbits. The path length difference is in particular based on the different starting positions or spatial distributions of the corresponding electrons at the electron emitter. The propagation toward the anode is carried out in particular by an acceleration unit, which in particular provides a high voltage between the cathode and the anode. In the context, the deflection of multiple electrons can in particular mean movement and / or focusing and / or defocusing while maintaining a relative spacing from each other. In the case of focusing or defocusing, at least one spacing between the electrons is changed by deflecting multiple electrons, in the case of focusing, in particular reducing the spacing, and in the case of defocusing, in particular increasing the spacing.

[0079] By fanning out and / or deflecting in the radial direction, the propagation of the emitted electrons typically takes place on a curved trajectory. The different trajectories of the emitted electrons are usually curved according to the curved trajectories. The curvature of the trajectories leads to the fact that the electrons can travel different path lengths along the respective trajectories until the electrons interact with the anode in the focal spot. The path length differences along the different trajectories of the electrons resulting from the curvature of the trajectories are advantageously taken into account by the design of the position-dependent forces of the inhomogeneous field. The inhomogeneous field can be designed in particular such that the electrons are subjected to different position-dependent forces depending on their trajectory.

[0080] It is conceivable that the inhomogeneous field is generated by the deflection unit depending on the magnitude of the high voltage between the cathode and the anode. The inhomogeneous field can be generated in particular in such a way that the cathode-side spatial distribution of the electrons differs from the anode-side spatial distribution of the electrons. Cathode side or anode side means in particular: after the electron emission at the cathode or before the electron strikes the anode. The difference in the spatial distribution between the cathode and the anode can be in different extensions, in particular extensions perpendicular to the axis of rotation, preferably different widths and / or different lengths.

[0081] One embodiment provides that the deflection unit surrounds the rotating tube housing in a plane perpendicular to the axis of rotation by less than 360°, in particular less than 180°. In this case, the deflection unit does not completely, in particular not largely, surround the rotating tube housing in the circumferential direction. This embodiment therefore offers the advantage of a smaller space requirement for the deflection unit.

[0082] One embodiment proposes that the inhomogeneous field is a magnetic field, and the deflection unit has a coil with a magnetic core in particular. In principle, it is conceivable that the deflection unit has a coil without a magnetic core. Alternatively, the deflection unit includes only a permanent magnet in particular. The deflection unit generates an inhomogeneous magnetic field in particular by means of a coil with a magnetic core. The coil is in particular a current flowing through it and / or has a plurality of windings. The plurality of windings can be distributed on a single winding package or a plurality of winding packages. The magnetic field generated by the coil with the magnetic core is static in particular during the emission time period. The embodiment is particularly advantageous because the inhomogeneous magnetic field is particularly suitable for taking into account the path length difference of the electrons. The magnetic core typically has a soft magnetic material and / or a ferrite or is a permanent magnet. In the case of a combination of a coil and a magnetic core, the inhomogeneous field is generated in particular by the coil and the magnetic core together. If the magnetic core is a permanent magnet in the case, the coil current of the coil can be advantageously reduced because the permanent magnet can compensate for the smaller magnetic field of the coil. The magnetic core advantageously reduces the required coil current intensity for realizing the magnetic field. Alternatively or additionally, the magnetic core can influence the field gradient of the inhomogeneous field. In particular, the deflection in length and / or width can thereby be influenced. Ideally, the higher moments of the magnetic field can be minimized by means of the magnetic core. Purely physically, the magnetic field typically has no effect in the direction of the (instantaneous) velocity of the electrons. Since the electrons fly essentially along the axis of rotation, the magnetic field is inhomogeneous, in particular, in a plane perpendicular to the axis of rotation.

[0083] It is conceivable that the coil comprises a plurality of packages with windings, wherein a plurality of winding packages are arranged at sections of the magnetic core that are angled with respect to one another. In other words, in the embodiment described, the center axis of the first winding package is at an angle not equal to 180° relative to the center axis of the second winding package, so that the two are not located on the same straight line. The number of winding packages can be two or three in particular. The winding packages and the sections of the magnetic core can be arranged and designed symmetrically with respect to one another.

[0084] The magnetic core may in particular have a curved shape. The magnetic core is in particular not rod-shaped. The curved shape may in particular be C-shaped. The ends of the magnetic core may include an angle that is not equal to zero. The angle may in particular be equal to or less than 180°. The angle may in particular be between 90° and 180°.

[0085] Alternatively or additionally, at least one end of the core or both ends of the core can be tilted. The tilting relates in this context to the bending direction of the core. In particular, the core is not tilted when the closed surface of the core forming the end is perpendicular to the bending direction of the core. Therefore, in particular, there is a tilt when the closed surface of the core forming the end is at an angle not equal to 90° relative to the bending direction.

[0086] The curved shape and / or the inclined ends mean in particular that the magnetic core is advantageously designed in such a way that the proportion of magnetic field lines running parallel outside the magnetic core is reduced, so that an inhomogeneous field is advantageously generated thereby.

[0087] One embodiment provides that the core is oriented so that the ends of the core are located in the same plane perpendicular to the axis of rotation and are oriented equidistantly relative to the axis of rotation. The ends of the core are located in particular at the same height relative to the axis of rotation. The equidistant orientation in particular enables a symmetrical orientation of the core around the axis of rotation.

[0088] One embodiment provides that the magnetic core is oriented in such a way that a plane perpendicular to the rotation axis, in which the ends of the magnetic core are located, intersects the rotation axis between the cathode and the anode. This embodiment is particularly advantageous because the deflection unit is arranged relatively close to the electrons.

[0089] One embodiment provides that the core is oriented so that the center axis of the winding of the coil is located in a plane perpendicular to the rotation axis in which the ends of the core are located. In this case, in particular, the ends of the core and the center axis of the winding are preferably located at the same height relative to the rotation axis. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] In the following, the present invention is described and explained in detail based on the embodiments shown in the drawings. In principle, in the following description of the drawings, structures and units that remain essentially the same are named with the same reference numerals as when the corresponding structure or unit first appears.

[0091] The accompanying drawings show:

[0092] Figure 1 The electron emitter in the first embodiment is shown,

[0093] Figure 2 The electron emitter in the second embodiment is shown in a first operating state,

[0094] Figure 3showing an electron emitter of a second embodiment in a second operating state,

[0095] Figure 4 An electron emitter in a third embodiment is shown,

[0096] Figure 5 A modified form of the electron emitter of the third embodiment is shown,

[0097] Figure 6 Another modified form of the electron emitter of the third embodiment is shown.

[0098] Figure 7 A further modified form of the electron emitter of the third embodiment is shown.

[0099] Figure 8 The rotating tube housing X-ray tube according to the present invention is shown.

[0100] Fig. 9 A variation of the rotating tube housing X-ray tube according to the present invention is shown.

[0101] Fig.10 The rotating tube shell X-ray radiator according to the present invention is shown.

[0102] Fig.11 shows a variant of the deflection unit,

[0103] Fig.12 Another variant of the deflection unit is shown,

[0104] Fig.13 A further variant of the deflection unit is shown.

[0105] Fig.14 A non-uniform field is shown. DETAILED DESCRIPTION

[0106] Figure 1 The electron emitter 10 in the first embodiment is shown.

[0107] The electron emitter 10 is suitable for a rotating tube envelope X-ray tube 30. The electron emitter 10 has a segmented emitter surface 11. The segmented emitter surface 11 has at least two emitter elements 12.E, 12.1, 12.2 that can be activated independently of each other and is configured to activate at least a subset of the segments of the segmented emitter surface 11 as an activated emission surface 11.A for emitting electrons from the activated emission surface 11.A.

[0108] At least one of the at least two emitter elements 12.1, 12.2 is designed for thermionic emission of electrons. The at least two emitter elements 12.E, 12.1, 12.2 are arranged close to one another such that a distance A between the respective emitter surfaces is minimal.

[0109] The at least two emitter elements 12.E, 12.1, 12.2 are arranged such that the segmented emitter surface 11 is designed to be axisymmetric in the emitter surface plane and, in the described exemplary embodiment, is essentially rotationally symmetrical. Figure 1 In the embodiment shown in , the axis of symmetry corresponds to a horizontal axis passing through the midpoint of the electron emitter 10 , and the rotational symmetry likewise relates to the midpoint which is interrupted only by the transport section 13 .

[0110] In the first embodiment, the segmented transmitter surface 11 is formed by two transmitter elements 12.1, 12.2. The first transmitter element 12.1 is formed in annular shape with a central opening 12. The second transmitter element 12.2 is arranged in the first transmitter element 12.1 in the central opening 12.Z. The shape of the central opening 12.Z is predetermined by the annular shape of the first transmitter element 12.1.

[0111] The first emitter element 12 . 1 is a spiral emitter. The second emitter element 12 . 2 can also be designed as a thermionic emitter element or as a field effect emitter element.

[0112] Figure 2 The electron emitter 10 in a second embodiment is shown in a first operating state. The second embodiment differs from the first embodiment in particular in the design of the emitter elements 12 .E, 12 . 1 , 12 . 2 .

[0113] The segmented emitter surface 11 formed by the two emitter elements 12.1, 12.2 is designed to be axisymmetrical and rectangular with respect to two mutually perpendicular spatial axes. The segmented emitter surface 11 is higher than it is wide and is in particular not square. The emitter elements 12.1, 12.2 are inserted into a circular cathode head 21.

[0114] The first operating state of the electron emitter 10 means that only one of the two emitter elements 12 . 1 , 12 . 2 is active and comprises an active emission area 11 .

[0115] Figure 3 The electron emitter 10 of the second embodiment is shown in a second operating state. In the second operating state, the two emitter elements 12 . 1 , 12 . 2 are active and form an active emission area 11 .

[0116] Figure 4An electron emitter 10 in a third embodiment is shown.

[0117] The segmented emitter surface 11 is composed of three emitter elements 12.1, 12.2, 12.3 arranged side by side in a straight line and has a height greater than width. The emitter surface of one of the emitter elements 12.1 is larger than the emitter surface of the other two emitter elements 12.2, 12.3 added together. For example, by additionally activating the other two emitter elements 12.2, 12.3, the focal spot generated by the activated emission surface of an electron emitter 12 can be enlarged. The segmented emitter surface 11 is axially symmetrical about two spatial axes perpendicular to each other and is rectangular in the exemplary embodiment.

[0118] Figure 5 A variant of the electron emitter 10 of the third embodiment is shown. In this case, each emitter element 12.1, 12.2, 12.3 is a spiral emitter.

[0119] Figure 6 Another variant of the electron emitter 10 of the third embodiment is shown. Here, the central emitter element 12.1 is a spiral emitter, and the emitter elements 12.2, 12.3 adjacent to the central emitter element 12.1 are non-spiral line emitters.

[0120] Figure 7 FIG. 2 shows another modified form of the electron emitter 10 of the third embodiment. Figure 6 The only difference compared to the exemplary embodiment shown in is that in each case two adjacent transmitter elements 12 . 1 , 12 . 2 , 12 . 3 are oriented to one another in such a way that the transmitter longitudinal directions are perpendicular to one another.

[0121] Figure 8 The rotating envelope X-ray tube 30 is shown in a longitudinal section along the axis A of rotation.

[0122] The rotating tube X-ray tube 30 has a cathode 20, a rotating shaft A and a rotating frequency relative to the cathode 20. Figure 8 The fixed support part (not shown) can support the evacuated rotating shell 31 and the anode 32. The cathode 30 and the anode 32 are connected to the rotating shell 31 in a rotationally fixed manner. The cathode 20 has a cathode head 21 and an electron emitter 10, which is inserted in a rotationally fixed manner into the cathode head 21. The rotating shell 31 is made of glass in the section 33 between the anode 32 and the cathode 20.

[0123] In addition, Figure 8As shown in FIG. 1 , the rotating shell 31 is cylindrical. The first end side of the cylindrical rotating shell 31 is configured to accommodate a cathode-side support member 34. The cathode 20 is fastened to the cathode-side support member 34. The second end side of the cylindrical rotating shell 31 is configured to accommodate an anode-side support member 35. The anode 32 is fastened to the anode-side support member 35. The cathode-side support member 34 and the anode-side support member 35 are configured to allow the rotating shell 31 to rotate relative to the rotating shell 31. Figure 8 3. The fixed support part (not shown) rotates around the rotation axis A in the rotation direction R or counter to the rotation direction R. The cathode-side support part 34 and the anode-side support part 35 each have an axis aligned with the rotation axis A. The axis rotates, for example, in the rotation direction R or counter to the rotation direction R and the rest of the rotating housing X-ray tube 30 rotates with the axis. The rotating housing 31 can be rotated around the rotation axis A by means of a ball bearing (not shown).

[0124] In the embodiment, the entire side surface of the rotating envelope 31 is composed of glass. The rotating envelope X-ray tube 30 is a bipolar high voltage tube in which a negative high voltage potential is applied at the cathode 20 and a positive high voltage potential is applied at the anode 32.

[0125] In the exemplary embodiment, the diameter of the rotating tube shell 31 perpendicular to the rotation axis A is less than 100 mm and is 85 mm. The length of the rotating tube shell 31 along the rotation axis A is less than 200 mm and is 156 mm. This length is suitable for insulating the glass bulb 30 between the cathode 20 and the anode 32 up to an acceleration voltage of 125 kV. For example, the negative high voltage potential can be -62.5 kV and the positive high voltage potential can be 62.5 kV. The spacing between the cathode 20 and the anode 32 is, for example, 90 mm, wherein the anode 32 has an anode angle of, in particular, 14°.

[0126] Fig. 9 A variant of a rotating envelope X-ray tube 30 is shown in a longitudinal section along the rotation axis A. In this variant, the anode angle of the anode 32 is 16° and the diameter of the rotating envelope 31 perpendicular to the rotation axis A is 65 mm.

[0127] Fig.10 A longitudinal section through a rotating tube housing X-ray radiator 40 is shown.

[0128] The rotating envelope X-ray radiator 40 has a housing 41, a rotating envelope X-ray tube 30 and a deflection unit 42. The rotating envelope X-ray tube 30 is supported rotatably relative to the housing 41 around a rotation axis A at a rotation frequency in the housing 41. The rotating envelope X-ray tube 30 has a cathode 20, a rotating envelope 31 and an anode 32. The anode 32 is connected to the rotating envelope 31 in a rotationally fixed manner. The cathode 20 has a cathode head 21 and an electron emitter 10 for emitting electrons inserted into the cathode head 21, and is arranged on the rotation axis A in the rotating envelope 31.

[0129] The deflection unit 42 is configured to generate an inhomogeneous field between the cathode 20 and the anode 32 in the rotating tube shell 31. The inhomogeneous field affects the emitted electrons to different trajectories toward the anode 32, and is designed to take into account the path length differences of the emitted electrons along different trajectories in the inhomogeneous field. If the deflection unit 42 has a coil with a magnetic core, then Fig.10 The central deflection unit 42 is designed, for example, such that a plane perpendicular to the rotation axis A, in which the ends of the magnetic core are located, intersects the rotation axis A between the cathode 20 and the anode 31 .

[0130] The rotating tube x-ray radiator 40 further comprises a fixed support part 43 which is connected to the housing 41 in a rotationally fixed manner. The fixed support part 43 cooperates in particular with the cathode-side support part 34 and the anode-side support part 35 to enable the rotating tube x-ray tube 30 to rotate relative to the housing 41.

[0131] Fig.11 Three views are shown of variants of the deflection unit 42. The deflection unit 42 surrounds the rotating tube housing 31 in a plane perpendicular to the axis of rotation A by less than 360°, in particular less than 180°.

[0132] The deflection unit 42 has a coil with a magnetic core. The magnetic core is oriented such that the ends of the magnetic core are located in the same plane perpendicular to the rotation axis A and are equidistant from the rotation axis A. The magnetic core is also oriented such that the center axis of the winding of the coil is located in a plane perpendicular to the rotation axis A in which the ends of the magnetic core are located. Furthermore, the magnetic core is designed such that the proportion of magnetic field lines running parallel outside the magnetic core is reduced.

[0133] In the upper row of the two views, the left side shows the deflection unit 42 with the rotating tube housing 31 in a front view and the right side shows the deflection unit 42 in a side view. In the lower row, a perspective view of the deflection unit 42 is shown.

[0134] Fig.12 A further variant of a deflection unit 42 is shown in a detail view. The inhomogeneous field is a magnetic field. The deflection unit 42 has a coil with a magnetic core. The magnetic core is bent and at least one end of the magnetic core (in the exemplary embodiment, both ends) is beveled.

[0135] Fig.13 Three views (from left to right: front view, side view, perspective view) of another variant of a deflection unit 42 are shown. The deflection unit 42 has a coil with a magnetic core. The coil comprises a plurality of packages with windings. The plurality of winding packages are arranged at sections of the magnetic core that are angled with respect to one another.

[0136] Fig.14 An inhomogeneous magnetic field is shown. The deflection unit 42 has a coil with a magnetic core. The magnetic field components are schematically plotted, from which the plotted course along the field lines shown in solid lines is obtained. An inhomogeneous magnetic field configured in this way is particularly advantageous, because Bx has a gradient in the negative y direction, and By has the sign of the x-axis and a gradient in the y direction.

[0137] In addition, Fig.14 The position of the central axis of rotation A is drawn purely by way of example at the height of the x-axis. A displacement of the axis of rotation A upwards or downwards along the y-axis can easily be envisaged.

[0138] Although the details of the present invention have been explained and described in detail through the preferred embodiments, the present invention is not limited to the disclosed examples, and other variations may be derived by those skilled in the art without departing from the scope of protection of the present invention.

Claims

1. An electron emitter (10) for a rotating tube housing X-ray tube (30), the electron emitter comprising: a segmented emitter surface (11), wherein the segmented emitter surface (11) has at least two emitter elements (12.E, 12.1, 12.2, 12.3) which can be activated independently of one another, and is configured to activate at least a subset of the segments of the segmented emitter surface (11) as an activated emission surface (11.A) for emitting electrons from the activated emission surface (11.A), wherein the at least two emitter elements (12.E, 12.1, 12.2, 12.3) are arranged such that the segmented emitter surface (11) is axially symmetrically formed in an emitter surface plane, wherein at least one emitter element (12.1, 12.2, 12.3) of the at least two emitter elements (12.E, 12.1, 12.2, 12.3) is configured for thermionic emission of electrons, It is characterized in that The at least two emitter elements (12.E, 12.1, 12.2, 12.3) are arranged close to one another in such a way that the distance (12.A) between the respective emitter surfaces is minimal.

2. The electron emitter (10) according to claim 1, The segmented transmitter surface (11) is formed by two transmitter elements (12.1, 12.2) and is essentially rotationally symmetrical, the first transmitter element (12.1) being formed annularly with a central opening (12.Z), and the second transmitter element (12.2) being arranged in the first transmitter element (12.1) in the central opening (12.Z).

3. The electron emitter (10) according to claim 2, The first transmitter element (12.1) is a helical transmitter.

4. The electron emitter (10) according to claim 1, The segmented emitter surface (11) is formed by two emitter elements (12.1, 12.2), is axially symmetrical and rectangular about two mutually perpendicular spatial axes, and the height of the segmented emitter surface (11) is greater than the width.

5. The electron emitter (10) according to claim 4, Wherein the first transmitter element (12.1) is a helical transmitter, and wherein the second transmitter element (12.2) is a helical transmitter.

6. The electron emitter (10) according to claim 1, The segmented emitter surface (11) is composed of three emitter elements (12.1, 12.2, 12.3) arranged side by side in a straight line and has a height greater than a width, and the emitter surface of one of the emitter elements (12.1) is greater than the emitter surface of the other two emitter elements (12.2, 12.3) added together.

7. The electron emitter (10) according to claim 6, Each transmitter element (12.1, 12.2, 12.3) is a spiral transmitter.

8. The electron emitter (10) according to claim 6, The central transmitter element (12.1) is a spiral transmitter, and the transmitter elements (12.2, 12.3) adjacent to the central transmitter element (12.1) are non-spiral line transmitters.

9. The electron emitter (10) according to claim 7 or 8, In each case, two adjacent transmitter elements (12.1, 12.2, 12.3) are oriented relative to one another in such a way that the transmitter longitudinal directions are perpendicular to one another.

10. A rotating tube housing X-ray tube, the rotating tube housing X-ray tube comprising: -cathode, - a rotating tube housing which can be evacuated and which can be supported at a rotational frequency about a rotation axis relative to a fixed support element, and -anode, wherein the cathode has: - cathode head, and - an electron emitter according to any one of the preceding claims, which is inserted into the cathode head in a rotationally fixed manner, The cathode and the anode are connected to the rotating tube in a rotationally fixed manner within the rotating tube.

11. The rotating tube housing X-ray tube according to claim 10, The rotating tube shell is composed of glass at least in a section between the cathode and the anode.

12. A rotating tube shell X-ray radiator, the rotating tube shell X-ray radiator comprising: -case, - a fixed support member, and - A rotating envelope X-ray tube according to any one of claims 10 or 11, The fixed bearing part is connected to the housing in a rotationally fixed manner, and the rotating tube housing X-ray tube is supported in the housing in a rotatable manner relative to the housing by means of the fixed bearing part.

13. The rotating tube shell X-ray radiator according to claim 12, The rotating tube shell X-ray radiator has a deflection unit, wherein the deflection unit is configured to generate an inhomogeneous field between the cathode and the anode in the rotating tube shell, wherein the inhomogeneous field affects the emitted electrons to cause them to be on different orbits toward the anode, and is designed to take into account the path length difference of the emitted electrons along the different orbits in the inhomogeneous field.

14. The rotating tube shell X-ray radiator according to claim 13, The deflection unit surrounds the rotating tube shell in a plane perpendicular to the rotation axis by less than 360°, in particular less than 180°.

15. The rotating tube shell X-ray radiator according to any one of claims 13 or 14, The inhomogeneous field is a magnetic field, and the deflection unit has a coil with a curved magnetic core.

Images