Electron guiding and receiving element

Abstract

The invention relates to an electron antenna as an anode for a micro- or nano-focus X-ray generation comprising an antenna base and an antenna element arranged on the antenna base such that the antenna element protrudes from a front surface of the antenna base, wherein the antenna is arranged to guide and attract the electrons in its vicinity to the top the antenna element.

Claims

1. Anode for an X-ray tube, characterized in that the anode comprises an electron antenna comprising an antenna element X-ray emitter; wherein the antenna element is arranged on an antenna base; the electron antenna is configured in the same spatial relation to a cathode cup as in a stationary anode X-ray tube or rotating anode X-ray tube, wherein an upper part of the antenna element protrudes out of and parallel to a front surface of the antenna base, wherein the protrusion of the antenna element and an aspect ratio of the antenna element cause a local enhancement of an electric field at a top end of the antenna element, wherein a height h of protrusion of the antenna element is between 1 m-5 mm from the antenna base and a top surface of the antenna element has an anode angle of 5-45.

2. The anode of claim 1, wherein the electron antenna comprises an antenna element in the shape of a blade, wherein the shape of the top surface of the blade is a cross, a square, a rectangle, linear segments, an elliptical disc or a circular disc.

3. The anode of claim 2, wherein a width t of the blade or of longitudinal sections of the cross, a long side of the rectangle, a side of the square or linear segments shape is between 10 nm-200 m.

4. The anode of claim 2, wherein the circular disc comprises a radius R200 m or where the elliptical disc has a semi-major axis r200 m.

5. The anode of claim 1, wherein the electron antenna works as replacement of an anode in vacuum tubes for generating single or multiple micro- or nano-focus X-ray beam; wherein the antenna element is metallic and comprises one or more of the metals: W, Rh, Mo, Cu, Co, Fe, Cr and Sc; or one or more of the alloys: WRe, WMo, MoFe, CrCo, FeAg and CoCuFe.

6. The anode of claim 1, wherein the antenna base comprises electrically conductive the material which is one or more of: Cu and Mo.

7. The anode of claim 1, wherein the antenna base comprises an electrically insulating material and wherein a plurality of antenna elements are arranged on the antenna base.

8. The anode of claim 7, wherein the electrically insulating material is one or more of: BN, Al.sub.2O.sub.3.

9. An X-ray generating device comprising the anode of claim 1.

10. The X-ray generating device of claim 9, wherein said X-ray generating device is a single hot cathode micro- or nano-focus tube by using a hot filament cathode.

11. The X-ray generating device of claim 10 comprising the said anode can be configured to a single field emission cathode micro- or nano-focus tube by using a field emission cathode.

12. The X-ray generating device of claim 11, wherein the field emission cathode can be further configured to allow for thermally assisted emission, such as Schottky emission.

13. The X-ray generating device of claim 10, wherein the X-ray generating device is a rotating anode micro- or nano-focus tube, wherein a plurality of antenna elements are radially embedded in a rotating antenna base disc.

14. The X-ray generating device of claim 9, wherein said X-ray generating device is a dual cathode micro- or nano-focus tube by using a cathode assembly holding a field emission cathode and a hot filament cathode.

15. The X-ray generating device of claim 14, wherein said X-ray generating device further comprises an electron emitter comprising a gate electrode, thereby making the X-ray generating device a triode field emission micro- or nano-focus tube.

16. The X-ray generating device of claim 9, wherein said X-ray generating device is a micro- or nano-focus tube with multiple excitation sources comprising multiple cathodes and anodes.

17. The X-ray generating device of claim 9, wherein the X-ray generating device is a rotating anode micro- or nano-focus tube, wherein one or a plurality of antenna elements are concentrically embedded in a rotating antenna base disc.

18. An apparatus comprising an X-ray generating device according to claim 1, wherein said apparatus is a computed tomography (CT) scanning apparatus, a C-arm type scanning apparatus, a mini C-arm type scanning apparatus, a geological surveying apparatus, an X-ray diffraction apparatus, X-ray fluorescence spectroscopy, an X-ray non-destructive testing apparatus, phase contrast imaging or in a colour CT scanner.

19. An anode for an X-ray tube, characterized in that the anode comprises an electron antenna comprising an antenna element X-ray emitter; wherein the antenna element is arranged on an antenna base; the electron antenna is configured in the same spatial relation to a cathode cup as in a stationary anode X-ray tube or rotating anode X-ray tube, wherein an upper part of the antenna element protrudes out of and parallel to a front surface of the antenna base, wherein the protrusion of the antenna element and an aspect ratio of the antenna element cause a local enhancement of an electric field at a top end of the antenna element, wherein the aspect ratio of a blade, defined as the division of a height h to a width t, is in the range of 10-100.

20. An anode for an X-ray tube, characterized in that the anode comprises an electron antenna comprising an antenna element X-ray emitter; wherein the antenna element is arranged on an antenna base; the electron antenna is configured in the same spatial relation to a cathode cup as in a stationary anode X-ray tube or rotating anode X-ray tube, wherein an upper part of the antenna element protrudes out of and parallel to a front surface of the antenna base, wherein the protrusion of the antenna element and an aspect ratio of the antenna element cause a local enhancement of an electric field at a top end of the antenna element, wherein a metallic antenna element is a tungsten blade and the antenna base comprises two half cylindrical copper parts, wherein the tungsten blade is sandwiched in between the two half cylindrical copper pieces in such a way that a first blade edge of the tungsten blade is protruding from a front surface of the copper cylinder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The foregoing will be apparent from the following more particular description of the example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments.

(2) FIGS. 1A-1C Schematically show prior art x-ray tubes: 1A is a schematic of an X-ray tube comprising a conventional anode, no micro-focus; 1B is a schematic of a micro focus X-ray tube comprising a conventional anode and electromagnetic lenses, 1C depicts micro focus X-ray generation using a liquid metal jet anode.

(3) FIG. 2 is an illustrative example of an electron antenna element, according to some of the example embodiments described herein;

(4) FIG. 3A is a schematic of an electron antenna comprising an antenna element and an antenna base, according to some of the example embodiments described herein.

(5) FIG. 3B is an illustration of the electron antenna and its physical principle for guiding and receiving electrons.

(6) FIG. 4 is an illustrative example of different shapes an electron antenna element may have, according to some of the example embodiments described herein;

(7) FIG. 5 is an illustration of an electrically conductive antenna base e.g. Cu for single antenna element in one example embodiment;

(8) FIG. 6 is a schematic of an electron antenna comprising multiple antenna elements when the antenna base is made of an insulating material, e.g. BN or Al2O3, according to some of the example embodiments described herein.

(9) FIG. 7 is a schematic of an X-ray tube comprising one hot cathode and an electron antenna.

(10) FIG. 8 is a schematic of an X-ray tube comprising one field emission cathode and an electron antenna.

(11) FIG. 9 is a schematic of an X-ray tube comprising a dual cathode, i.e. one field emission cathode and one hot filament cathode; and an electron antenna.

(12) FIG. 10 is a schematic of an X-ray tube comprising a field emission cathode, a gate electrode and an electron antenna.

(13) FIG. 11A and FIG. 11B are graphs illustrating two types of rotating anode tube solution using the electron antenna, according to some of the example embodiments described herein.

DETAILED DESCRIPTION

(14) In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular components, elements, techniques, etc. in order to provide a thorough understanding of the example embodiments. However, it will be apparent to one skilled in the art that the example embodiments may be practiced in other manners that apparently depart from but inherently connected to these specific details. In other instances, detailed descriptions of well-known methods and elements are omitted so as not to obscure the description of the example embodiments. The terminology used herein is for the purpose of describing the example embodiments and is not intended to limit the embodiments presented herein.

(15) Problems:

(16) In order to better describe the example embodiments, a problem will first be identified and discussed. FIG. 1A illustrates a traditional X-ray tube. The X-ray tube of FIG. 01A features an evacuated glass tube 0100 comprising a hot filament cathode 0110 and a W-disc anode 0120 embedded in a Cu-cylinder 0130. The surface of the anode 0120 faces the cathode 0110 at a predetermined inclination angle or anode angle. An electric current, provided by a power supply 0140, passes through the filament cathode 0110 causing an increase in the temperature of the filament 0110 to a level for it to emit a beam of electrons 0150 from this filament. The electrons in the beam 0150 are then accelerated towards the anode 0120 by a potential difference provided by a power source 0160. The resulting X-ray beam 0170 is directed out of the device via a window 0180. The voltage difference between the cathode and the anode determines the energy of the X-ray beam, not micro-focus. A typical double banana shaped focal spot is indicated by 0190.

(17) FIG. 1B is a schematic of a prior art micro-focus X-ray device comprising a transmission anode 0120 and electromagnetic lenses 0145. The lenses add extra size and weight, and cost to the tube 0100; and needs an additional power source 0165 to drive the lenses and to be synchronized with the output voltage of the tube. Therefore this type of micro-focus tubes has issues concerning the size and weight and cost, and lateral drift of the X-ray beam. For further information, see for instance, www.phoenix-xray.com.

(18) FIG. 1C is a schematic of prior art micro focus X-ray generation using a liquid metal jet anode 0175. The electron beam 0150 hits the liquid metal jet 0175 resulting in an X-ray beam 0170. The liquid metal jet anodes require a so called open tube meaning that the high vacuum condition is maintained by continuous pumping of the tube. Such solution is bulky and expensive. In addition, anode materials are limited to the metals with low melting temperature. For further information, see for instance www.excillum.com

(19) Example Embodiments:

(20) Example embodiments presented herein are directed towards an electron guiding and receiving element or an electron antenna comprising an antenna element and an antenna base, which is configured to receive electrons not as a signal for communication but as stimuli for electromagnetic radiation. Example embodiments are further directed towards x-ray tubes comprising the said electron antenna.

(21) The electron antenna comprises an antenna element and an antenna base. The antenna element is structured and configured to receive all electrons coming towards it and confine them into a predefined region, whereas the antenna base is structured and configured to conduct the heat electricity and/or electricity.

(22) Antenna Element:

(23) FIG. 2 is an illustrative example of an electron antenna element 0200 shaped to a thin blade, according to some of the example embodiments described herein; with the top surface or top edge 0210 of the element intended to receiving the electrons. 0220 indicates the two faces of the antenna element, denotes the inclination angle or anode angle, t denotes the thickness of the blade, and L denotes the length of the top surface. The maximum length of the top surface is 10 mm, and can vary from 10 mm down to nanometers. The anode angle can vary between a few degrees, e.g. 5 degrees to 45 degrees. The dimension of the cross section and the inclination angle of the blade define the dimension of focal spot of the X-ray beam such that the width of the blade limits the width of the focal spot, and the length of the focal spot is limited by I=L sin . The holes 0230 are for positioning and fixing the element with respect to the antenna base. The L and t of the antenna element can be made in various sizes to meet the need for the size of the X-ray focal spot. A preferred range is from (L=10, t=0.1) mm down to a disc of radius of 10 nm. In high power applications, however, the focal spot area can be as big as 88 mm.sup.2.

(24) FIG. 3A is a schematic of an electron antenna according to one example embodiment described herein, 0300 is the blade shaped antenna element sandwiched between two half cylindrical blocks 0310 forming the antenna base 0320 with the two faces 0220 of the antenna element 0300 in contact with the antenna base 0320. In one example embodiment two half cylindrical Cu blocks 0310 act as the antenna base 0320. The upper part of the blade is configured to protrude out of and in parallel to an inclined front surface of the cylinder 0330. The height of the protrusion h is in a range of 0.001-5 mm and is determined in proportion to the focal spot size. The aspect ratio, defined as the division of the height to the width, h/t, is in the range of 10-100.

(25) FIG. 3B shows a schematic side view of an assembly of a hot filament cathode and the electron antenna, and illustrates the guiding and focusing principle of the antenna. The assembly comprises a cathode cup 0305, a hot filament 0315, the electron beam 0325, the electron antenna element 0335, and the antenna base 0345. As can be seen, the entire electron beam is focused on the antenna element 0335.

(26) The antenna element can be made of various metals, including but not limited to W, Rh, Mo, Cu, Co, Fe, Cr and Sc etc.; or alloys, including but not limited to WRe, WMo, MoFe, CrCo, FeAg and CoCuFe etc. to meet the requirements for specific applications.

(27) FIG. 4 is an illustration of different shapes an electron antenna element may have, according to some of the example embodiments described herein. The top surface of the antenna element can be made in various shapes to meet the need for the shape of the X-ray focal spot, including but not limited to cross 0410, circular disc 0420, elliptical disc 0430, square 0440, rectangle 0450 and several kinds of linear segments 0460-80. 0490 is the top view of 0480, and so can the entire antenna element be. The edges of the top surfaces can be smoothed to satisfy certain need for specific distribution of local electric field. It is noted that the shape of the top surface reflects directly or indirectly the shape of the cross section of the antenna element.

(28) The diameter of the circular disc, the semi-major axis of elliptical disc, the side of square, and the long side of the rectangle may be between 10 nm-10 mm.

(29) Antenna Base:

(30) The antenna base is made of various metals, alloys, compounds or composites preferably possessing high electrical conductivity, high thermal conductivity, high melting temperature and machinability or formability. In preferred embodiment, the materials include but not limited to Cu, Mo, BN, and Al2O3.

(31) FIG. 5 is an illustration of an electrically conductive antenna base e.g. Cu for single antenna element in one example embodiment, 0510 is the side view of the antenna base, and 0520 is the top view of the antenna base. A beneficial feature of an electrically conductive base is that it can be used as the electrical feed through.

(32) FIG. 6 is a schematic of an antenna base made of an electrical insulating material, e.g. BN or Al2O3, according to some of the example embodiments described herein; 0610 is the side view of an antenna element, and 0620 is one of the multiple antenna elements sandwiched in parallel between BN or Al2O3 blocks acting as insulating antenna base 0630. In this case, multiple antenna elements can be assembled to constitute a multiple focal spots tube. It ought to be noted that these antenna elements 0620 can be made of not necessarily the same material.

(33) Fusion of Antenna Element and Antenna Base:

(34) The surfaces of the antenna element that are in contact with the base can be coated with a thin layer of the same material as the base or a material intermediate between the base and the antenna element to enhance the thermal and/or electrical affinity between the antenna element and the base. The layer may have a thickness of between 10 m and 50 nm.

(35) The fusion or joining of the antenna element and the antenna base can be made by mechanical pressure supplied from screws and/or pivots or by vacuum casting.

(36) Configuration in X-ray Tube:

(37) The antenna is configured in the same spatial relation to the cathode cup as in a normal stationary anode X-ray tube or rotating anode X-ray tube.

(38) X-ray Devices:

(39) The example embodiments presented herein are directed towards an X-ray device comprising the said electron antenna. The features of the X-ray device in later figures that are unaltered with respect to those of earlier figures have the same numbering. An X-ray device comprising the said electron antenna can be configured to a single hot cathode micro- or nano-focus tube, when combined with one hot filament cathode.

(40) FIG. 7 is a schematic of such an X-ray tube comprising a single hot cathode 0110 and an electron antenna; where 0720 and 0730 denote the antenna element and the antenna base, respectively.

(41) An X-ray device comprising the said electron antenna can be configured to a single field emission cathode micro- or nano-focus tube, when combined with one field emission cathode.

(42) FIG. 8 is a schematic of such an X-ray tube comprising one field emission cathode 0810 and electron antenna comprising one antenna element 0720 and antenna base 0730.

(43) An X-ray device comprising the said electron antenna can also be configured to a dual cathode micro- or nano-focus tube, when combined with a cathode cup holding one field emission cathode and one hot filament cathode.

(44) FIG. 9 is a schematic of such an X-ray tube comprising dual cathode, i.e. one field emission cathode and one hot filament cathode; and an electron antenna comprising an antenna element 0720 and an antenna base 0730; where 0910 denotes a cathode cup holding the dual cathode, and 0140 denotes the power unit for the hot filament cathode.

(45) An X-ray device comprising the said electron antenna can as well be configured to a micro- or nan-focus tube with multiple excitation sources comprising multiple (thermionic or field emission) cathodes and electron antenna elements, when an insulating antenna base is used; see FIG. 6 for a schematic of such a multiple elements antenna, 0620 and 0630 for the antenna elements and the antenna base, respectively.

(46) An X-ray device comprising the said electron antenna can further be configured to a triode field emission micro- or nano-focus tube, when combined with a field electron emitter comprising a gate electrode.

(47) FIG. 10 is a schematic of such an X-ray tube comprising a field emission cathode 0810 and its power unit 0820, a gate electrode 1010, and one electron antenna comprising an antenna element 0720 and antenna base 0730.

(48) The field emission cathode can be further configured to allow for thermally assisted emission, such as Schottky emission.

(49) An X-ray device comprising the said electron antenna can be configured to one type of rotating anode micro- or nano-focus tube, when single or multiple antenna elements are circularly sandwiched in the rotating disc.

(50) FIG. 11A illustrates this type of rotating anode solution, according to some of the example embodiments described herein; where 1110 denotes the rotating disc acting as the antenna base, 1120 and 1130 are two circular antenna elements sandwiched in the antenna base. The antenna base 1110 is seen from the above. There can be more than two antenna filaments in other embodiments. And the material of the antenna elements can be made different.

(51) An X-ray device comprising the said electron antenna can be configured to another type of rotating anode micro- or nano-focus tube, when multiple antenna elements are radially sandwiched in the rotating disc with equal angular-space.

(52) FIG. 11B illustrates this type of rotating anode solution, according to some of the example embodiments described herein; where 1105 denotes one of the antenna elements, 1115 denotes the rotating disc acting as the antenna base, and 1125 indicates the angular space between the antenna elements with denoting its value. The number of antenna elements is determined by the pulse frequency of the electron emission and the speed of rotation. The antenna base 1115 is seen from above.

(53) Example Advantages of Embodiments:

(54) The concept of electron antenna and its use in X-ray tube redesign allow for a simpler and more economic approach to more compact micro or nano focus X-ray tubes than the liquid jet anode approach and the conventional approach of using electromagnetic lenses between the cathode and the anode. In the latter, even though the focal spot size can be focused to nanometre range, the drift of the focal spot can be significant, which is caused by among other factors the instability of the voltages applied to the lenses and the cathode and anode (Newsletter 01/2015, X-RAY WorX GmbH). The use of the said electron antenna is able to provide a drift-free focal spot whose size is in a range of millimetre down to nanometre scale. The drift-free focal spot is guaranteed by facts that the focal spot size is determined by the electron antenna element that is fixed mechanically to the solid antenna base and thus free from any motion. In addition, the shape of the antenna element and its large contact area to the antenna base provide a superior heat management solution. The use of the said electron antenna also allows the resulting micro focus tubes to be used in applications where macro focus tubes dominated prior.

(55) Applications:

(56) It should be appreciated that the X-ray device described herein may be used in a number of fields. For example, the X-ray device may be used in a security scanning apparatus, as one would find in an airport security check and post terminal.

(57) A further example use of the X-ray device discussed herein is in medical scanning devices such as a computed tomography (CT) scanning apparatus or a C-arm type scanning apparatus, which may include a mini C-arm apparatus. A few example application of the X-ray device may be mammography, veterinary imaging and dental imaging.

(58) A further example use of the X-ray device described herein is in a geological surveying apparatus, X-ray diffraction apparatus and X-ray fluorescence spectrometry, etc.

(59) It should be appreciated that the X-ray device described herein may be used in any non-destructive testing apparatus.

(60) It should be appreciated that the X-ray device described herein may be used in phase contrast imaging and colour CT scanner.

(61) As previously mentioned the electron antenna works also for production of radiation with wavelengths other than X-rays. By replacing the metallic electron antenna element in the above description for production of an X-ray beam with an antenna element comprising UV light emitting material, such as quantum wells or quantum dots, production of UV light is possible. An improved focus of a UV light beam has similar advantages as for an X-ray beam. The drift-free focal spot is guaranteed by facts that the focal spot size is determined by the electron antenna element that is fixed mechanically to the solid antenna base and thus free from any motion. In addition, the shape of the antenna element and its large contact area to the antenna base provide a superior heat management solution. The use of the said electron antenna also allows the resulting micro focus tubes to be used in applications where macro focus tubes dominated prior.

(62) Similarly, by replacing the metallic electron antenna element in the above description for production of an X-ray beam with an antenna element comprising visible light emitting material, such as a phosphorescent or fluorescent material, production of visible light is possible. An improved focus of a visible light beam has similar advantages as for an X-ray beam. The drift-free focal spot is guaranteed by facts that the focal spot size is determined by the electron antenna element that is fixed mechanically to the solid antenna base and thus free from any motion. In addition, the shape of the antenna element and its large contact area to the antenna base provide a superior heat management solution. The use of the said electron antenna also allows the resulting micro focus tubes to be used in applications where macro focus tubes dominated prior.

(63) The description of the example embodiments provided herein have been presented for purposes of illustration. The description is not intended to be exhaustive or to limit example embodiments to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of various alternatives to the provided embodiments. The examples discussed herein were chosen and described in order to explain the principles and the nature of various example embodiments and its practical application to enable one skilled in the art to utilize the example embodiments in various manners and with various modifications as are suited to the particular use contemplated. The features of the embodiments described herein may be combined in all possible combinations of methods, apparatus, modules, systems, and computer program products. It should be appreciated that the example embodiments presented herein may be practiced in any combination with each other.

(64) It should be noted that the word comprising does not necessarily exclude the presence of other elements or steps than those listed and the words a or an preceding an element do not exclude the presence of a plurality of such elements. It should further be noted that any reference signs do not limit the scope of the claims, that the example embodiments may be implemented at least in part by means of both hardware and software, and that several means, units or devices may be represented by the same item of hardware.

(65) In the drawings and specification, there have been disclosed exemplary embodiments. However, many variations and modifications can be made to these embodiments. Accordingly, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the embodiments being defined by the following claims.