Title of Invention	"MODULAR X-RAY TUBE AND METHOD OF PRODUCTION THEREOF"
Abstract	Modular X-ray tube (10) and method for the production of such an X-ray tube, in which an anode (20) and a cathode (30) are arranged in a vacuurnized inner space (40) situated opposite each other, electrons (e) being produced at the cathode (30) and X-rays (y) at the anode (20), the X-ray tube (10) comprising a multiplicity of acceleration modules (41,... ,45), complementing one another. Each of these acceleration module (41,... ,45) comprises at least one potential-carrying electrode (20/30/423/433/443), a first acceleration module (41) comprising the cathode (30) with electron extraction (e), and a second acceleration module (45) comprising the anode (20) with the X ray generation (y). The X-ray tube (10) according to the invention comprises at least one further acceleration module (42,... ,44) with a potential-carrying electrode (423/433/443), the acceleration module (42,... ,44) for acceleration of electrons (e) being repeatedly connectible in series as often as desired, and the X-ray tube (10) being of modular construction.

Title of Invention

"MODULAR X-RAY TUBE AND METHOD OF PRODUCTION THEREOF"

Abstract

Modular X-ray tube (10) and method for the production of such an X-ray tube, in which an anode (20) and a cathode (30) are arranged in a vacuurnized inner space (40) situated opposite each other, electrons (e) being produced at the cathode (30) and X-rays (y) at the anode (20), the X-ray tube (10) comprising a multiplicity of acceleration modules (41,... ,45), complementing one another. Each of these acceleration module (41,... ,45) comprises at least one potential-carrying electrode (20/30/423/433/443), a first acceleration module (41) comprising the cathode (30) with electron extraction (e), and a second acceleration module (45) comprising the anode (20) with the X ray generation (y). The X-ray tube (10) according to the invention comprises at least one further acceleration module (42,... ,44) with a potential-carrying electrode (423/433/443), the acceleration module (42,... ,44) for acceleration of electrons (e) being repeatedly connectible in series as often as desired, and the X-ray tube (10) being of modular construction.

Full Text	Modular X-ray Tube and Method of Production Thereof The present invention relates to an X-ray tube for high dose rates, a corresponding method for producing high dose rates with X-ray tubes as well as a method of production of corresponding X-ray devices, in which an anode and a cathode are disposed situated opposite each other in a vacuumized inner space, electrons being accelerated to the anode by means of impressible high voltage. In scientific and technical applications, the use of X-ray tubes is widespread. X-ray tubes not only find application in medicine, e.g. in diagnostic systems or with therapeutic systems for irradiation of diseased tissue, but are also employed e.g. for sterilization of substances such as blood or foodstuffs, or for sterilization (making infertile) of creatures such as insects. Other areas of application are to be further found in classical X-ray technology such as e.g. x-raying pieces of luggage and/or transport contairtefs, or nondestructive testing of wortcpieoes, e.g. concrete feiniomements, etc. Diverse metiiods and devices for X-wy tubes are described in the state of the art These range from miniaturized tubes in the form of a transistor hotising to high pen\)mianoe tubes wan an accotoraSon voltage of up to 450 tatovott. Espectafty in recent times a great deal of time, effort and expense in industry and technology has been put toward improving the capacity and/or efficiency and/or service Kfe and/or maintenance possibttties of systems of irradiation. These efforts have been triggered in particular by new demands relating to security systems, such as e.g. during irradiation of large freight containers in air traffic, etc., and similar devices. The conventional X-ray tube types used in the industrial environment consist either of glass or metal-ceramic composite materials. Figure 1 shows schematically an example of such a conventional X-ray tube made of a composite glass material. Figures 2 and 3 show conventional X-ray tubes made of a composite metal material. In the X-ray tubes, electrons in a vacuumized tube pass through an electrical field. They are thereby accelerated to their ultimate energy, and convert this on a target surface into X-radiation. This means that X-ray tubes comprise an anode and a cathode which are disposed in a vacuumized inner space situated opposite each other, and are enclosed in the metal-ceramic tubes by a cylindrical metal part (Figure 2/3) and in glass tubes by a glass cylinder (Figure 1). In glass tubes, the glass acts as insulator. In the metal-ceramic tubes, on the other hand, anode and/or cathode are usually electrically insulated by means of a ceramic insulator, the ceramic insulator or Insulators being disposed axialty with respect to the metal cylinder, behind the anode and/or cathode, and terminating the vacuum space at the respective end. The ceramic insulators are typically designed discokial (annular) or conical. In principle, any desired insulator geometry would be possible with this tube type, whereby field super-elevations are to be taken into consideration at high voltages. As a rule, the ceramic insulators have an opening at their center in which a high voltage supply to the anode, or the cathode, are inserted in a vacuum-tight way. This kind of X-ray tubes are designated in the stale of the art as two-pole or bipolar X-ray tubes (Figure 3). Distinguished therefrom are so-cafed unipolar devices (Rgure 2). in which the aoode. le. » target is set at ground potential. With the bipolar systems, the electron source (cathode) is set at a negative high voltage (HV). and the target (anode) at a positive high voltage. With al constructions of Ihe state of the art. however, the fuM acceleration voltage for acceleration of electrons (single stage) is impressed between anode and cathode. It is to be noted that solutions exist in which an aperture located at ground (intermediate aperture) is mounted between anode and cathode. This intermediate aperture can serve, on the one hand, as an electron-optical lens, but also as a mechanical shutter for electrons scattered back from the target. The problems or the drawbacks that arise from this one-stage construction are owing to the fact that the probability of interfering physical effects grows with increasing impressed voltage. These limit at the present time the X-ray tubes of the state of the art in the case of unipolar tubes to maximally about 200 to 300 kV and in the case of bipolar devices to maximally about 450 kV impressed voltage. As just mentioned, it is the further physical effects, such as e.g. field emission, secondary electron emission, and photo effect, which arise in addition to the desired generation of X rays during operation of an X ray tube, that limit the operational capability of the tubes. Not only do these effects disturb the operation of the X-ray tube, but they can lead to damage of the material and thus to a premature fatigue of the components. In particular, secondary electron emission is known to interfere with X-ray tube functioning. During secondary electron emission, with impingement of the electron beam on the anode, undesired, but unavoidable secondary electrons arise, in addition to the X rays, which secondary electrons move away in the interior of the X-ray tube on paths corresponding to the field lines. Through various scattering and impact methods, these secondary electrons can end up on the insulator surface, and reduce the HV insulation characteristics there. Secondary electrons also arise, however, in that the insulators at the anode and/or cathode are hit during operation by unavoidable filed emission electrons and trigger secondary electrons there. With switched-on high voltage at the anode and cathode, i.e. during operation of the X-ray tube, the electric field is generated in the inner space and at the surfaces turned towards the inner space. This also includes the surfaces of the insulator. The shorter the X-ray lube is and the wider the ceramic insulator is, the greater the ptobabitty that secondary otoctrons ancyor Bald emission oloclroos impinge on Ihe oetaroic part or parts. This results in toe high voltage stabWy arc) service fife of the device being reduced in an undesirable way. Wtthdfeooidal insulators, therefore, use of so-catod sttokfng electrodes is known from the state of the art, e.g. from DE2865905. The snicking oloctiodoa can be used e.g. in pairs, these being usually disposed coaxialry at a certain spacing distance in the case of a rotationaHy symmetrical design of the X-ray tube, in order to prevent in an optimal way the propagation of secondary electrons. As has been shown, however, such devices can no longer be used with very high voltage. Furthermore the material and manufacturing costs are greater with such constructions than in the case of X-ray tubes having just insulators. Another possibility from the state of the art is shown, for example, in DE6946926. In order to decrease the attack surfaces, a conical ceramic insulator is used in these solutions. The ceramic insulator has a substantially constant wall thickness, and is e.g. covered with a vulcanized rubber layer. The layer is supposed to contribute to secondary electrons arising less intensely. As mentioned, the electric field inside the vacuum space also comprises the surfaces of the insulators. In particular with conical insulators, an electron impinging on the insulators or a stray electron triggered by an impinging electron is accelerated by the field away from the surface in the direction of the anode. In principle, the insulation cones are shaped in such a way that the normal vector of the electric field accelerates the electrons away from the insulator surface. If the anode-side insulator as well as the cathode-side insulator are designed as truncated cone projecting into the inner space, then an electron impinging on the insulator (for example one released from the metal piston) will likewise be accelerated towards the anode. The anode-side cone of the insulator is shaped e.g. such mat the normal vector points away from the surface. Anode-side the electron moves along the insulator surface because no electric field pointing away from the insulator surface has an affect upon the electron. After traversing a certain distance, such an electron has sufficient energy to trigger further electrons, which, for their part, release in turn electrons, so that there arises on the insulator surface an electron avalanche toward the anode, which can cause a significant malfunction, in certain circumstances also gas eruptions or even a breakdown of the insulator. The riigf»er» voltage is, the nwro signified With very high voltages, Ms kind of insutator can ttwraforo be no longer used. Moreover it is field. Dapondhig upon onorgy and angle of emission, electrons can also run in the dtoetfon of the cathode, in particular in the case of stray or scatter electrons. Cathode-side the effect described above occurs less frequently, since electrons which end up on the insulator surface cathode-side or are released therefrom, move through the vacuum in the direction of the metal cylinder and not along the insulator surface. To get around the disadvantage, various solutions are known in the state of the art; tor example, proposed in the unexamined German publication DE2506841 is to design the insulator cathode-side such mat a conical hollow space exists between the insulator and the tube. Another solution of the state of the art is shown e.g. in the patent publication EP0215034, where the discoidal insulator is tiered in a stepped way toward the metal cylinder. It has been shown, however, that all the solutions shown in the state of the art have malfunctions at high voltages, i.e. for instance above 150 kV, which lead to a premature aging of the material, among other things, and can cause gas eruptions and/or breakdown of the insulator. Thus the X-ray tubes known in the state of the art are poorly suited, or not usable at all, for many modem applications with very high voltages (>400 kV). It is an object of this invention to propose a new X-ray tube and a corresponding method of production of such an X-ray tube not having the drawbacks described above. In particular, an X-ray device should be proposed allowing electric powers several times higher than conventional X-ray devices. The tubes should also be able to be constructed modulariy, and be produced simply and economically. Furthermore any possible defective parts of the X-ray tube should be replaceable without the whole X-ray tube having to be replaced. This object is achieved according to the present invention in particular through the elements of the independent claims. Further advantageous embodiments follow moreover from the dependent claims and from the specification. These objects are achieved in particular through the invention in that an anode and a cathode are disposed opposite each other in a vacuumized inner apace in an X-ray tube, electrons being produced at the cathode, being accelerated to the anode by means of knpressibte high voltage, and X rays being produced at the anode by means of the electrons, (he X-ray tube cnmpnaingamuttipidtycrfnKjCuaty which accokxation modules each ex>mprise at least ere pcrtential-cafiying electrode, the first acceleration module comprising the cathode with primary electron generation, and tie last acceleration module comprising the anode with the X-ray generation, and the X-ray tube comprising at least one further acceleration module with a potential-carrying electrode, which acceleration module is connectibte in series in a repeatabte way as often as desired for acceleration of electrons, and the X-ray tube being of modular construction. The anode can comprise a target for X-ray generation with an emission hole, or can be designed as a transmission anode, in the case of the transmission anode the vacuumized inner space of the X-ray tube being closed off toward the outside. At least one of the electrodes can comprise spherical or conical ends for reducing or minimizing the field peak at the respective electrode. The electrodes can be connected, for example, with a high voltage cascade, e.g. by means of voltage connections. One advantage, among others, of the invention is that very high power X-radiation can be generated, the overall geometric size of the X-ray tube being smaN, Hi particular compared with tubes of the state of the art, and at the same time the invention makes possible an X-ray tube which is able to be operated in a stable manner over a very broad electrical voltage range without performance characteristics changing. A further advantage of the invention, among others, is a by far more minimal stress on the insulator from the E- field. This appNes in particular when compared with the conventional discoidal insulators. The X-ray tube according to tiie invention can be produced e.g. in a one-shot method, the soldering of the entire tube taking place in a one-step vacuum soldering process. This has in particular the advantage that the subsequent evacuation of the X-ray tube by means of high vacuum pump can be omitted, tt is a further advantage that the X-ray tube according to the invention, owing to its simple and modular construction, is especially well suited to the ora-«Hot method since the fields inside the tube am muoh smaller than in th«oa««of ooiw«ntona1tub««. and the tuba aoocmingtotoeinvaottonis m to be constant for at acceleration modules, the final eneigy of the accelerated electrons (el being a whole-number multiple of the energy of an acceleration module. This eiiibodtaent variant riastneadvant^ stress on the insulators is constant over the path, and no field peaks occur that could have a disadvantageous effect upon the operating abttty of the tube. In another embodiment variant at least one of the acceleration modules has a redosabte vacuum valve. The acceleration modules can thereby be provided with a a vacuum seal on one side or on both sides in order to permit an air-tight closure between the individual acceleration modules. This embodiment variant has the advantage, among others, that by means of the vacuum valve individual parts of the X-ray tube can be replaced without the entire tube having to be replaced, as in the case of conventional X-ray tubes. Since the tube is of modular construction, the tube is able to be subsequently adapted to changed operational requirements without any difficulty by further acceleration modules being inserted or existing modules removed. This is not possible in this way with any of the tubes of the state of the art. In a further embodiment variant, the acceleration modules contain a cylindrical ceramic insulator. This embodiment variant has the advantage, among others, that in the case of moderate stress from the electric field, the mechanical, design-engineering effort is minimal, extraordinarily high performance characteristics being attainable. In another embodiment variant, the ceramic insulator has a high-ohmic interior coating. This embodiment variant has the advantage, among others, that disruptive charging by scattered electrons, provoked on the one hand by field-related processes in the insulator material, on the other hand by secondary electrons scattered back from the anode target and by field emission electrons, is avoided. The service life of the X-ray tubes and/or the differences in potential between the individual acceleration electrodes can thereby be further increased. In an embodiment variant, tfie ceramic insulator 53 comprises a ridged exterior structure. Through the shape of ttie ceramic insulator 53, the insulating section on the exterior (atmospheric side) of the insulator can be lengthened. This embodknont variant has the advantage, among othocb, that it has an exterior structure suitably shaped for toe high voltage. This exterior structure enables moreover an irnpioved, mom effk^ent cooing of the X-ray tube. In an embodiment variant, the electrodes of the acceleration modules include a shield for suppression of the stray electron flow on the ceramic insulator. At least one of the shields can comprise spherically or contcaRy designed ends for reducing or minimizing the field peak at the respective shield. This embodiment variant has the advantage, among others, that the shields constitute supplementary protection for the ceramic insulator. The service life of the X-ray tubes and/or the differences in potential between the individual electrodes can thereby be further increased. In an embodiment variant, the X-ray tube according to the invention is produced in a one-shot method. This has the advantage, among others, that the subsequent evacuation of the X-ray tube 10 by means of high vacuum pump can be omitted. A further advantage of the one-shot method, i.e. the one-step manufacturing process by total soldering of the tube in the vacuum (one-shot method), is, among others, that one has a single manufacturing process, and not three, as in the conventional way: 1. soldering of components / 2. joining together of components (e.g. soldering or welding) / 3. evacuating tube by means of vacuum pump. The one-step production method is thus economically more efficient, time-saving, and cheaper. At the same time, with suitable process control, contamination of the tube can be minimized with this method. Anyhow it can be advantageous when the tube is free of impurities to a large extent that, as a rule, minimize the ceramic insulator's ability to withstand voltage. The requirements with respect to vacuum tightness for the tubes 10 are in most cases the same with one-shot methods as with multi-step manufacturing processes. It should be stated here that besides the method according to the invention, the present invention also relates to a device for carrying out this rnelrod as wei as a n>ethod of production of sudi a device. In particular it also relates to feradfaifon systems comprising at least one X-cay tube according to the invention wtth one or mom high voltage cascades for voUaqe supply of the at least one X-ray tube. Emboolment variants of the present invention wN te described in the fottowtog with reference to examples. The examples of the embodiments are illustrated by the following attached figures: Rgure 1 shows a block diagram representing schematically an X-ray tube 10 made of a glass compound of the state of the art. Electrons e" are thereby emitted from a cathode 30, and X rays y emitted from an anode 20, through a hole 201. 50 is a cylindrical glass tube, the glass serving as insulator. Figure 2 shows a block diagram representing schematically a unipolar X-ray tube 10 made of a metal-ceramic compound of the state of the art. 51 is the ceramic insulator, 52 the metal cylinder put on ground. Electrons e are thereby emitted from a cathode 30, and X rays y emitted from an anode 20, through a hole 201. Figure 3 shows a block diagram representing schematically a bipolar X-ray tube 10, likewise made of a metal-ceramic compound of the state of the art. 51 is the ceramic insulator, 52 the metallic cylinder put on ground. Electrons e* are thereby emitted from a cathode 30, and X rays y from an anode 20, through a hole 201. Figure 4 shows a block diagram, representing schematically an example of an external view of an X-ray tube 10 according to the invention. Figure 5 shows a block diagram representing schematically the architecture of an embodiment variant of an X-ray tube 10 according to the invention. Electrons e' are thereby emitted from a cathode 30, and X rays y are emitted from an anode 20. The X-ray tube 10 comprises a plurality of mutually cornpiementafy acceleration modules 41 ,...,45, and each acceleration module comprises at toast one potential-carrying electrode 20/30/423/433/443. Rgure 6 shows a block dtegram. representing schematically the architecture of a further ernbodwnent variant of an X-ray tube 10 accoidmg to the invention. AsinFioure3, theX-raylube 10oon^pnsesapkiraltyof mutuafty cornpternerttary acceleration modules 41 ,...,45 with voltage-carrying electrodes 20/30/423/433/443. The acceleration modules comprise in addition electron shields 422/432/442 for suppression of the stray electron flow on the ceramic insulator. Figure 7 likewise shows a block diagram representing schematically the architecture of another embodiment variant of an X-ray tube 10 according to the invention. As in Figure 3, the X-ray tube 10 comprises a plurality of mutually complementary acceleration modules 41 ,...,45 with voltage-carrying electrodes 20/30/423/433/443. At least one of the acceleration modules 41 45 comprises in addition a reclosable vacuum valve 531. Figure 8 shows a cross section of an X-ray tube 10 according to the invention, representing schematicaHy the architecture of an embodiment variant according to Figure 3. Figure 9 shows another cross-sectional view of an X-ray tube 10 according to the invention. The acceleration modules 41 ,...,45 comprise additionally a possible embodiment for shields 423.. .443 for suppression of the stray electron flow on the ceramic insulator. This embodiment variant has the advantage, among others, that the shields constitute supplementary protection for the ceramic insulator. The service life of the X-ray tubes and/or the difference in potential between the individual acceleration electrodes can thereby be further increased. The possible embodiment of Figure 9 shows spherically or conicalty designed ends of the electrodes 423/433/443 and/or of the shields 412,...,415 for reducing or minimizing the field peak at the respective electrode 423/433/443 and/or shield 412,...,415. The electrodes 423/433/443 are connective by voltage connections, e.g. to a high voltage cascade. Figure 10 shows the principle structure of an acceleration stage of a modular matt-ceramic tube wUh a modular hKHstep acceleration phase wittt two accotorotton modules 42/43 with ceramic insutatof 50. accokxalion electrodes 423/433 and voltage connections 421/431. Figure 11 shows schematicaiy the potential dfetrtoution in a modular X-ray tube 10 according to the invention from an embodiment example with a • SOOkVtube. Figure 12 shows schematically an irradiation system 60 with an X-ray tube 10 according to the invention. The irradiation system 60 comprises a high voltage cascade 62 for voltage supply of the X-ray tube 10, a high voltage transformer 63 as weN as an emission hole 61 for X-radiation y out of the shield housing 65. Figure 13 shows a further embodiment variant of three acceleration modules 42/43/44 with ceramic insulator 50, electron shield 422/432/442 and acceleration electrodes 423/433/443. Figure 4 to 10 Hlustrate architectures as they can be used to achieve the invention. In these embodiment examples for a modular X-ray tube 10, an anode 20 and a cathode 30 are disposed opposite each other in a vacuumized inner space 40. The electrons e* are generated at the cathode 30, the cathode 30 serving as electron emitter. The cathode 30 thus serves the purpose, on the one hand, of generation of the electric field E, but, on the other hand, also the purpose of electron generation. Thus in principle all materials which can emit the electrons e* are suitable for this application. This process can be achieved through thermal emission, but also through field emission (cold emission). Used as cold emitters can be e.g. any kind of micro-tip arrays with usually diamond-like structures or e.g. also nano tubes. Of course cold emission can also be used with this tube type by using the Penning Effect on suitably formed metals. For instance, thermal emitters can be used that are also usable with this emitter concept, such as e.g. tungsten (W). lanthanum hexaboride (LaBe), dispenser cathodes (La in W) and/or oxide cathodes (e.g. ZrO). The electrons e* are accelerated to the anode 20 by means of impressible Ngh voltage, and generate Xrays yon a taigat surface of the anode 20. The anodes 20 fuMI two functions in the X-fay tubes 10. On the one hand they serve as positive electrode 20 for generation of an electric ReM E for acceleration of the electrons e. On the other hand, the anodes 20, or respectively the target roaterid enibedded to fte anodes 20. setv^ energy is converted into X-radtetion y. This conversion is, on the one hand, dependent on the particle energy, but also on the atomic number of the target material. In a first approximation, according to the Bethe formula, the energy loss of the particles is equal to the square of the atomic number Z of the target material dW/ «Z2 With this process the anode 20 is thermally stressed. The anode or respectively the target material must therefore be able to withstand this thermal stress. It follows therefrom that the vapor pressure of the target material should be sufficiently low at operating temperature of the target in order not to influence in a negative way the vacuum necessary for operation of the X-ray tube 10. Thus target materials may preferably be used which are high-temperature-resistant or can be weN cooled. For this purpose the target material can be embedded in a good material capable of conducting heat (e.g. copper), which is abte to be wed cooled, i.e. conducts heat well. For example, materials as heavy and temperature-resistant as possible can therefore be used as anode (target) 20. In particular, suitable therefor are e.g. materials such as tungsten (W, Z=74) and/or uranium (U, 2=92) and/or rhodium (Rh, Z=45) and/or silver (Ag, 2=47) and/or molybdenum (Mo, 2=42) and/or palladium (Pd, Z=46) and/or iron (Fe, 2=26) and/or copper (Cu, 2=29). In selecting the target material, it can be particularly advantageous, e.g. for analytical applications, to take into consideration that the characteristic lines are suitable for the specific application purpose. The X-ray tube 10 further comprises a plurality of mutually complementary acceleration modules 41 ..... 45. Each acceleration module 41 ..... 45 comprises at least one potential-carrying electrode 20/30/423/433/443 with the corresponolng voltage connections 421/431/441 . A first acceleration module 41 comprises the cathode 30 with the electron generation e. i.e. with the etectoon emitter . A second •ccotoratton modute 45 comprises the anode 20 with toe X-radtaticNiY The Xay tube comprises at toast one further accotoratton module 42,...,44 with a poterrtial-cariving electrode 423/433/443. aaiurnizedinriersp8»40(^ means of ceramic insulator 51. For the emissim concept accotcRng to Ihe invention, insulation materials can be used, for example, which satisfy the electric requirements of the X-ray tube 10 (field strength). For corresponding embodiment examples, the insulation materials should also be suitable for producing a metal-ceramic compound. In addition, the ceramic should be usable for high vacuum applications. Thus suitable materials are, for example, pure oxide ceramics, such as aluminum oxide, magnesium oxide, beryllium oxide and zirconium oxide. Also monocrystalline AfeOa (sapphire) is in principle suitable. Furthermore so-called glass ceramics, such as e.g. Macor®, or similar materials are conceivable. In particular, composite ceramics are of course also suitable (e.g. doped AfeOa), if they have the respective characteristics. The insulation ceramics 51 can be designed e.g. outwardly ridged, or in a similar way, in order to lengthen the insulation section of the insulation jacket 51 that is not vacuum-side, i.e. is situated in insulating oil. In the same way, however, any other design of the ceramic insulator 51, e.g. a pure cylindrical form, is conceivable, without affecting the core of the invention. The ceramic insulator 51 can have in addition e.g. a high-ohmic interior coating in order to divert possible charges which can be caused by various electronic processes, it being ensured at the same time that the acceleration voltage is able to be impressed. Figure 8 shows the principle structure of a modular metal-ceramic tube of two such further acceleration modules 42/43 with ceramic insulator 51, acceleration electrodes 423/433 and potential connections 421/431. The principle described here for construction of X-ray tubes 10, being composed e.g. of a metal-ceramic compound, can be series-connected according to the invention as often as desired, and can thus be used for acceleration of electrons e~ (multiphase acceleration). The last potential-carrying electrode of the acceleration structure is the anode 20, necessary for generation. On the other hand, the cathode 30, necessary for electron generation, represents the first electrode of the acceleration structure. This is shown in the embodiment examples of Figures 4 to 9. With suitable configuration and selection of the etectrodes, X-ray tubes 10 with a total energy c up to 800 Wove* or ITIO^ RgureS). In contrast, conventional X-ray lubes untf now have been abte to be pio Electrons e* are thereby emitted from an electron emitter, i.e. a cathode 20, as a rule a hot tungsten coH, are accelerated toward a target through an impressed high voltage, X rays Y being radiated from the target, i.e. the anode 30, through a hole 301. Triple points (field peaks which lead to field emission of electrons e*) occur thereby both cathode-side as well as anode-side. The difference in potential between each two potential-carrying electrodes 20/30/423/433/443 of adjacent acceleration modules 41 ,...,45 can be selected to be constant e.g. also for all acceleration modules 41,...,45, the final energy of the accelerated electrons e' being a whole number multiple of the energy of an acceleration module 41 45. At least one of the acceleration rrK>dules 41.....45 can furtfier apprise a re It is important to point out that with the X-ray tubes 10 according to the invention a modularity in principle exists, i.e. the increase in the radiance energy of an X-ray tube 10 can be achieved by adding one or more acceleration segments 41 45 or acceleration modules 41 ,...,45. At least one of the acceleration modules 41 ,...,45 can thereby be constructed such that it bears a rectosabte vacuum valve. The acceleration modules 41 ,...,45 can further comprise vacuum seals on one side or on both sides. This has the advantage that individual defective acceleration modules 41 ,...,45 can be simply replaced and/or recycled by a defective tube 10 being devacuumized using the rectosable vacuum valve 531, the defective acceleration module 41 ,...,45 being replaced by a new and/or functioning one, and the tube 10 being vacuumized again using a corresponding vacuum pump via the reclosable vacuum valve 531. It is also important to point out that the electrodes 20/30/423/433/443 of the acceleration modules 41,...,45 can comprise a shielding 412,. .,415 for suppression of the stray electron flow on the ceramic insulator 51 (Figure 6/13). This has the advantage that the shields constitute supplementary protection for the ceramic insulators 51. The service life of the X-ray tubes and/or the difference in potential between the individual acceleration electrodes 20/30/423/433/443 can thereby be further increased. The simple and modular construction of the X-ray tube 10 according to the invention is especially well suited to a manufacturing process with a one-shot method, or respectively this design makes possible in principle the one-shot method in an efficient way. The soldering of the entire tube 10 takes place thereby in a one-step vacuum soldering process. This has the advantage, among others, that the subsequent evacuation of the X-ray tube 10 by means of high vacuum pump can be omitted. A further advantage of the one-shot method, i.e. of the one-step manufacturing process by means of the overall soldering of the tube in the vacuum (one-shot method), is. among others, that one has a single production process, and not three, as in the conventional way: 1. soldering off components / 2. joining of components (e.g. soldering or weldtog) / 3. evacuation of the tube by nteans of vacuum pump. The one-step manufacturing method is therefore eoo«iofnic^ more eMk^ent time-saving and cheaper. At the same time, with suitable process controi coritanfMnatkxi of the lubes can be minimized with this method. Anyhow it can be advantageous when toe tube is free of impurities to a targe extent which, as a nJe, minimize the ceramic insulator's ability to withstand voltage. Trie requirements with respect to vacuum tightness for the tubes 10 are in most cases the same with one-shot methods as with multi-step manufacturing processes. Since the fields inside the tube 10 are much smaller than in the case of conventional tubes, the tube 10 according to the invention is moreover less vulnerable to impurities and/or leaks. This makes the X-ray tube 10 according to the invention further suitable for the one-shot method. The X-ray tube 10 according to the invention can be excellently used for manufacture of an entire irradiation system and/or for individual irradiation devices 60 (see Figure 12). In such an irradiation device 60, the tube 10 can be stored in a housing 65, e.g. in insulating oil. The shield housing 65 can include an emission hole 61 for X-radiation Y- The irradiation device 60 comprises for the tube 10 a corresponding high voltage cascade 62, e.g. with an assigned high voltage transformer 63 and voltage connections 64 to the outside. Such irradiation devices 60 or monobtocks 60 can then be used e.g. for manufacture of larger Nraolation systems. Of course it is dear to one skilled in the art in the field that the tube 10 according to the invention, without target or transmission anode, is also excellently suited as electron emitter and/or electron cannon with the corresponding industrial areas of application owing to its simple, modular construction and its high performance. For the implementation according to the invention, it can be expedient for the shields 422/432/442 to be shaped such that the electron beam does not "see" any insulator surface 51 (Figure 13). Charging effects of the ceramic insulators 51 can result through impression of the acceleration voltage, which effects do not necessarily have to be caused by stray and secondary electron emission. By means of a geometry shown in Figure 13, or a simitar geometry, such charging effects can be prevented or diminished. A coating of the ceramic insulator can also be used in particular for feed of the potential, if e.g. a suitable conductive coaling is added outside on the insulatofs, so thoft the coaling ads as voltage UMcJoi. A suitable coaling against toe vacuumized inner space could also replace feemetaffc electrodes 423/433/443. TW8 would have ttte consequence, however, that one no longer rtasanyshtekftngasinFtgure 13. As an ernbocirnent example it would be possible e.g. to put a heical layer on the inner side (vacuum) of toe ceramic insulator 51 acting as voltage divider, and thus replacing the series of metallic electrodes 423/433/443. WE CLAIM 1. An X-ray lube (10) in which an anode (20) and a eathode (30) are disposed opposite each other in a vacuumizcd inner space (40), electrons (e) being able to be produced at the cathode (30), being able to be accelerated to the anode (20) by means of impressible high voltage, and X rays (y) being able to be produced at the anode (20) by means of the electrons (c"), the X-ray tube (10) comprising a multiplicity of mutually complementary acceleration modules (41,...,45), each acceleration module (41,...,45) comprising at least one potential-carrying electrode (20/30/423/433/443), a first acceleration module (41) comprising the cathode (30) with electron extraction (e), and a second acceleration module (45) comprising the anode (20) with the X ray generation (y), wherein the X-ray tube (10) comprises at least one further acceleration module (42,...,44) with a potential-carrying electrode (423/433/443), the acceleration module (42,.. .,44) for acceleration of electrons (e) being repeatedly connectible in series as often as desired, and the X-ray tube (10) being of modular construction. 2. 'fhe X-ray tube (10) as claimed in claim 1, wherein the difference in potential between each two potential-carrying electrodes (20/30/423/433/443) of adjacent acceleration modules (41,...,45) is constant for all acceleration modules (41,...,45), the final energy of the accelerated electrons (e") being a whole-number multiple of the energy of an acceleration module (41,...,45). 3. The X-ray tube (10) as claimed in claims 1 or 2, wherein at least one of the acceleration modules (41,...,45) has a reclosable vacuum valve (531) and/or vacuum seals on one side or on two sides. 4. The X-ray tube (10) as claimed in claims 1 to 3, wherein the acceleration modules (41,...,45) include a cylindrical ceramic insulator (53). 5. The X-ray tube (10) as claimed in claim 4, wherein the insulating ceramic (53) has a high-ohmic interior coating. 6. The X-ray tube (10) as claimed in claims 4 or 5, wherein the ceramic insulator (53) comprises a ridged exterior structure. 7. The X-ray tube (10) as claimed in claims 1 to 6, wherein the anode (20) comprises a target for X-ray generation as well as an emission hole (201) for X-radiation. 8. The X-ray tube (10) as claimed in claims 1 to 6, wherein the anode (20) includes a transmission anode, the transmission anode closing off the vacuumizcd inner space (40) toward the outside. 9. The X-ray tube (10) as claimed in claims 1 to 7, wherein the electrodes (20/30/423/433/443) of the acceleration modules (41,...,45) include a shield (412,...,415) for suppression of the stray electron flow on the ceramic insulator (51). 10. The X-ray tube (10) as claimed in claim 9, wherein at least one of the electrodes (423/433/443) and/or shields (412,...,415) comprises spherically or conically designed ends for reducing or minimizing the field peak at the respective electrode (423/433/443) and/or shield (412,...,415). 11. An irradiation system (60), wherein the irradiation system (60) comprises at least one X-ray tube (10) according to one of the claims 1 to 10 with a high voltage cascade (62) for voltage supply of the X-ray tube (10). 12. A method of production of an X-ray tube (10) according to one of the claims 1 to 10, wherein the X-ray tube (10) is produced in a one-step vacuum soldering process.

Full Text

Modular X-ray Tube and Method of Production Thereof
The present invention relates to an X-ray tube for high dose rates, a corresponding method for producing high dose rates with X-ray tubes as well as a method of production of corresponding X-ray devices, in which an anode and a cathode are disposed situated opposite each other in a vacuumized inner space, electrons being accelerated to the anode by means of impressible high voltage.
In scientific and technical applications, the use of X-ray tubes is widespread. X-ray tubes not only find application in medicine, e.g. in diagnostic systems or with therapeutic systems for irradiation of diseased tissue, but are also employed e.g. for sterilization of substances such as blood or foodstuffs, or for sterilization (making infertile) of creatures such as insects. Other areas of application are to be further found in classical X-ray technology such as e.g. x-raying pieces of luggage and/or transport contairtefs, or nondestructive testing of wortcpieoes, e.g. concrete feiniomements, etc. Diverse metiiods and devices for X-wy tubes are described in the state of the art These range from miniaturized tubes in the form of a transistor hotising to high pen\)mianoe tubes wan an accotoraSon voltage of up to 450 tatovott. Espectafty in recent times a great deal of time, effort and expense in industry and technology has been put toward improving the capacity and/or efficiency and/or service Kfe and/or maintenance possibttties of systems of irradiation. These efforts have been triggered in particular by new demands relating to security systems, such as e.g. during irradiation of large freight containers in air traffic, etc., and similar devices.
The conventional X-ray tube types used in the industrial environment consist either of glass or metal-ceramic composite materials. Figure 1 shows schematically an example of such a conventional X-ray tube made of a composite glass material. Figures 2 and 3 show conventional X-ray tubes made of a composite metal material. In the X-ray tubes, electrons in a vacuumized tube pass through an electrical field. They are thereby accelerated to their ultimate energy, and convert this on a target surface into X-radiation. This means that X-ray tubes comprise an anode and a cathode which are
disposed in a vacuumized inner space situated opposite each other, and are enclosed in the metal-ceramic tubes by a cylindrical metal part (Figure 2/3) and in glass tubes by a glass cylinder (Figure 1). In glass tubes, the glass acts as insulator. In the metal-ceramic tubes, on the other hand, anode and/or cathode are usually electrically insulated by means of a ceramic insulator, the ceramic insulator or Insulators being disposed axialty with respect to the metal cylinder, behind the anode and/or cathode, and terminating the vacuum space at the respective end. The ceramic insulators are typically designed discokial (annular) or conical. In principle, any desired insulator geometry would be possible with this tube type, whereby field super-elevations are to be taken into consideration at high voltages. As a rule, the ceramic insulators have an opening at their center in which a high voltage supply to the anode, or the cathode, are inserted in a vacuum-tight way. This kind of X-ray tubes are designated in the stale of the art as two-pole or bipolar X-ray tubes (Figure 3). Distinguished therefrom are so-cafed unipolar devices (Rgure 2). in which the aoode. le. *» target is set at ground potential. With the bipolar systems, the electron source (cathode) is set at a negative high voltage (HV). and the target (anode) at a positive high voltage. With al constructions of Ihe state of the art. however, the fuM acceleration voltage for acceleration of electrons (single stage) is impressed between anode and cathode. It is to be noted that solutions exist in which an aperture located at ground (intermediate aperture) is mounted between anode and cathode. This intermediate aperture can serve, on the one hand, as an electron-optical lens, but also as a mechanical shutter for electrons scattered back from the target.
The problems or the drawbacks that arise from this one-stage construction are owing to the fact that the probability of interfering physical effects grows with increasing impressed voltage. These limit at the present time the X-ray tubes of the state of the art in the case of unipolar tubes to maximally about 200 to 300 kV and in the case of bipolar devices to maximally about 450 kV impressed voltage. As just mentioned, it is the further physical effects, such as e.g. field emission, secondary electron emission, and photo effect, which arise in addition to the desired generation of X rays during operation of an X ray tube, that limit the operational capability of the tubes. Not only do these effects disturb the operation of the X-ray tube, but they can lead
to damage of the material and thus to a premature fatigue of the components. In particular, secondary electron emission is known to interfere with X-ray tube functioning. During secondary electron emission, with impingement of the electron beam on the anode, undesired, but unavoidable secondary electrons arise, in addition to the X rays, which secondary electrons move away in the interior of the X-ray tube on paths corresponding to the field lines. Through various scattering and impact methods, these secondary electrons can end up on the insulator surface, and reduce the HV insulation characteristics there. Secondary electrons also arise, however, in that the insulators at the anode and/or cathode are hit during operation by unavoidable filed emission electrons and trigger secondary electrons there. With switched-on high voltage at the anode and cathode, i.e. during operation of the X-ray tube, the electric field is generated in the inner space and at the surfaces turned towards the inner space. This also includes the surfaces of the insulator. The shorter the X-ray lube is and the wider the ceramic insulator is, the greater the ptobabitty that secondary otoctrons ancyor Bald emission oloclroos impinge on Ihe oetaroic part or parts. This results in toe high voltage stabWy arc) service fife of the device being reduced in an undesirable way. Wtthdfeooidal insulators, therefore, use of so-catod sttokfng electrodes is known from the state of the art, e.g. from DE2865905. The snicking oloctiodoa can be used e.g. in pairs, these being usually disposed coaxialry at a certain spacing distance in the case of a rotationaHy symmetrical design of the X-ray tube, in order to prevent in an optimal way the propagation of secondary electrons. As has been shown, however, such devices can no longer be used with very high voltage. Furthermore the material and manufacturing costs are greater with such constructions than in the case of X-ray tubes having just insulators. Another possibility from the state of the art is shown, for example, in DE6946926. In order to decrease the attack surfaces, a conical ceramic insulator is used in these solutions. The ceramic insulator has a substantially constant wall thickness, and is e.g. covered with a vulcanized rubber layer. The layer is supposed to contribute to secondary electrons arising less intensely. As mentioned, the electric field inside the vacuum space also comprises the surfaces of the insulators. In particular with conical insulators, an electron impinging on the insulators or a stray electron triggered by an impinging electron is accelerated by the field away from the surface in the direction of the
anode. In principle, the insulation cones are shaped in such a way that the
normal vector of the electric field accelerates the electrons away from the
insulator surface. If the anode-side insulator as well as the cathode-side
insulator are designed as truncated cone projecting into the inner space, then
an electron impinging on the insulator (for example one released from the metal
piston) will likewise be accelerated towards the anode. The anode-side cone of
the insulator is shaped e.g. such mat the normal vector points away from the
surface. Anode-side the electron moves along the insulator surface because
no electric field pointing away from the insulator surface has an affect upon the
electron. After traversing a certain distance, such an electron has sufficient
energy to trigger further electrons, which, for their part, release in turn
electrons, so that there arises on the insulator surface an electron avalanche
toward the anode, which can cause a significant malfunction, in certain
circumstances also gas eruptions or even a breakdown of the insulator. The
riigf»er*» voltage is, the nwro signified With very high
voltages, Ms kind of insutator can ttwraforo be no longer used. Moreover it is
field. Dapondhig upon onorgy and angle of emission, electrons can also run in the dtoetfon of the cathode, in particular in the case of stray or scatter electrons. Cathode-side the effect described above occurs less frequently, since electrons which end up on the insulator surface cathode-side or are released therefrom, move through the vacuum in the direction of the metal cylinder and not along the insulator surface. To get around the disadvantage, various solutions are known in the state of the art; tor example, proposed in the unexamined German publication DE2506841 is to design the insulator cathode-side such mat a conical hollow space exists between the insulator and the tube. Another solution of the state of the art is shown e.g. in the patent publication EP0215034, where the discoidal insulator is tiered in a stepped way toward the metal cylinder. It has been shown, however, that all the solutions shown in the state of the art have malfunctions at high voltages, i.e. for instance above 150 kV, which lead to a premature aging of the material, among other things, and can cause gas eruptions and/or breakdown of the insulator. Thus the X-ray tubes known in the state of the art are poorly suited, or not usable at all, for many modem applications with very high voltages (>400 kV).
It is an object of this invention to propose a new X-ray tube and a corresponding method of production of such an X-ray tube not having the drawbacks described above. In particular, an X-ray device should be proposed allowing electric powers several times higher than conventional X-ray devices. The tubes should also be able to be constructed modulariy, and be produced simply and economically. Furthermore any possible defective parts of the X-ray tube should be replaceable without the whole X-ray tube having to be replaced.
This object is achieved according to the present invention in particular through the elements of the independent claims. Further advantageous embodiments follow moreover from the dependent claims and from the specification.
These objects are achieved in particular through the invention in that an anode and a cathode are disposed opposite each other in a vacuumized inner apace in an X-ray tube, electrons being produced at the cathode, being accelerated to the anode by means of knpressibte high voltage, and X rays being produced at the anode by means of the electrons, (he X-ray tube cnmpnaingamuttipidtycrfnKjCuaty
which accokxation modules each ex>mprise at least ere pcrtential-cafiying electrode, the first acceleration module comprising the cathode with primary electron generation, and tie last acceleration module comprising the anode with the X-ray generation, and the X-ray tube comprising at least one further acceleration module with a potential-carrying electrode, which acceleration module is connectibte in series in a repeatabte way as often as desired for acceleration of electrons, and the X-ray tube being of modular construction. The anode can comprise a target for X-ray generation with an emission hole, or can be designed as a transmission anode, in the case of the transmission anode the vacuumized inner space of the X-ray tube being closed off toward the outside. At least one of the electrodes can comprise spherical or conical ends for reducing or minimizing the field peak at the respective electrode. The electrodes can be connected, for example, with a high voltage cascade, e.g. by
means of voltage connections. One advantage, among others, of the invention is that very high power X-radiation can be generated, the overall geometric size of the X-ray tube being smaN, Hi particular compared with tubes of the state of the art, and at the same time the invention makes possible an X-ray tube which is able to be operated in a stable manner over a very broad electrical voltage range without performance characteristics changing. A further advantage of the invention, among others, is a by far more minimal stress on the insulator from the E- field. This appNes in particular when compared with the conventional discoidal insulators. The X-ray tube according to tiie invention can be produced e.g. in a one-shot method, the soldering of the entire tube taking place in a one-step vacuum soldering process. This has in particular the advantage that the subsequent evacuation of the X-ray tube by means of high vacuum pump can be omitted, tt is a further advantage that the X-ray tube according to the invention, owing to its simple and modular construction, is especially well suited to the ora-«Hot method since the fields inside the tube am muoh smaller than in th«oa««of ooiw«ntona1tub««. and the tuba aoocmingtotoeinvaottonis
m
to be constant for at acceleration modules, the final eneigy of the accelerated electrons (el being a whole-number multiple of the energy of an acceleration module. This eiiibodtaent variant riastneadvant^ stress on the insulators is constant over the path, and no field peaks occur that could have a disadvantageous effect upon the operating abttty of the tube.
In another embodiment variant at least one of the acceleration modules has a redosabte vacuum valve. The acceleration modules can thereby be provided with a a vacuum seal on one side or on both sides in order to permit an air-tight closure between the individual acceleration modules. This embodiment variant has the advantage, among others, that by means of
the vacuum valve individual parts of the X-ray tube can be replaced without the entire tube having to be replaced, as in the case of conventional X-ray tubes. Since the tube is of modular construction, the tube is able to be subsequently adapted to changed operational requirements without any difficulty by further acceleration modules being inserted or existing modules removed. This is not possible in this way with any of the tubes of the state of the art.
In a further embodiment variant, the acceleration modules contain a cylindrical ceramic insulator. This embodiment variant has the advantage,
among others, that in the case of moderate stress from the electric field, the mechanical, design-engineering effort is minimal, extraordinarily high performance characteristics being attainable.
In another embodiment variant, the ceramic insulator has a high-ohmic interior coating. This embodiment variant has the advantage, among others, that disruptive charging by scattered electrons, provoked on the one hand by field-related processes in the insulator material, on the other hand by secondary electrons scattered back from the anode target and by field emission electrons, is avoided. The service life of the X-ray tubes and/or the differences in potential between the individual acceleration electrodes can thereby be further increased.
In an embodiment variant, tfie ceramic insulator 53 comprises a ridged exterior structure. Through the shape of ttie ceramic insulator 53, the insulating section on the exterior (atmospheric side) of the insulator can be lengthened. This embodknont variant has the advantage, among othocb, that it has an exterior structure suitably shaped for toe high voltage. This exterior structure enables moreover an irnpioved, mom effk^ent cooing of the X-ray tube.
In an embodiment variant, the electrodes of the acceleration modules include a shield for suppression of the stray electron flow on the ceramic insulator. At least one of the shields can comprise spherically or contcaRy designed ends for reducing or minimizing the field peak at the respective shield. This embodiment variant has the advantage, among others, that the shields constitute supplementary protection for the ceramic insulator. The service life of the X-ray tubes and/or the differences in potential between the individual electrodes can thereby be further increased.
In an embodiment variant, the X-ray tube according to the invention is produced in a one-shot method. This has the advantage, among others, that the subsequent evacuation of the X-ray tube 10 by means of high vacuum pump can be omitted. A further advantage of the one-shot method, i.e. the one-step manufacturing process by total soldering of the tube in the vacuum
(one-shot method), is, among others, that one has a single manufacturing process, and not three, as in the conventional way: 1. soldering of components / 2. joining together of components (e.g. soldering or welding) / 3. evacuating tube by means of vacuum pump. The one-step production method is thus economically more efficient, time-saving, and cheaper. At the same time, with suitable process control, contamination of the tube can be minimized with this method. Anyhow it can be advantageous when the tube is free of impurities to a large extent that, as a rule, minimize the ceramic insulator's ability to withstand voltage. The requirements with respect to vacuum tightness for the tubes 10 are in most cases the same with one-shot methods as with multi-step manufacturing processes.
It should be stated here that besides the method according to the invention, the present invention also relates to a device for carrying out this rnelr*od as wei as a n>ethod of production of sudi a device. In particular it also relates to feradfaifon systems comprising at least one X-cay tube according to the invention wtth one or mom high voltage cascades for voUaqe supply of the at least one X-ray tube.
Emboolment variants of the present invention wN te described in the fottowtog with reference to examples. The examples of the embodiments are illustrated by the following attached figures:
Rgure 1 shows a block diagram representing schematically an X-ray tube 10 made of a glass compound of the state of the art. Electrons e" are thereby emitted from a cathode 30, and X rays y emitted from an anode 20, through a hole 201. 50 is a cylindrical glass tube, the glass serving as insulator.
Figure 2 shows a block diagram representing schematically a unipolar X-ray tube 10 made of a metal-ceramic compound of the state of the art. 51 is the ceramic insulator, 52 the metal cylinder put on ground. Electrons e* are thereby emitted from a cathode 30, and X rays y emitted from an anode 20, through a hole 201.
Figure 3 shows a block diagram representing schematically a bipolar X-ray tube 10, likewise made of a metal-ceramic compound of the state of the art. 51 is the ceramic insulator, 52 the metallic cylinder put on ground. Electrons e* are thereby emitted from a cathode 30, and X rays y from an anode 20, through a hole 201.
Figure 4 shows a block diagram, representing schematically an example of an external view of an X-ray tube 10 according to the invention.
Figure 5 shows a block diagram representing schematically the architecture of an embodiment variant of an X-ray tube 10 according to the invention. Electrons e' are thereby emitted from a cathode 30, and X rays y are emitted from an anode 20. The X-ray tube 10 comprises a plurality of mutually cornpiementafy acceleration modules 41 ,...,45, and each acceleration module comprises at toast one potential-carrying electrode 20/30/423/433/443.
Rgure 6 shows a block dtegram. representing schematically the architecture of a further ernbodwnent variant of an X-ray tube 10 accoidmg to the invention. AsinFioure3, theX-raylube 10oon^pnsesapkiraltyof mutuafty cornpternerttary acceleration modules 41 ,...,45 with voltage-carrying electrodes 20/30/423/433/443. The acceleration modules comprise in addition electron shields 422/432/442 for suppression of the stray electron flow on the ceramic insulator.
Figure 7 likewise shows a block diagram representing schematically
the architecture of another embodiment variant of an X-ray tube 10 according to
the invention. As in Figure 3, the X-ray tube 10 comprises a plurality of
mutually complementary acceleration modules 41 ,...,45 with voltage-carrying
electrodes 20/30/423/433/443. At least one of the acceleration modules
41 45 comprises in addition a reclosable vacuum valve 531.
Figure 8 shows a cross section of an X-ray tube 10 according to the invention, representing schematicaHy the architecture of an embodiment variant according to Figure 3.
Figure 9 shows another cross-sectional view of an X-ray tube 10 according to the invention. The acceleration modules 41 ,...,45 comprise additionally a possible embodiment for shields 423.. .443 for suppression of the stray electron flow on the ceramic insulator. This embodiment variant has the advantage, among others, that the shields constitute supplementary protection for the ceramic insulator. The service life of the X-ray tubes and/or the difference in potential between the individual acceleration electrodes can thereby be further increased. The possible embodiment of Figure 9 shows spherically or conicalty designed ends of the electrodes 423/433/443 and/or of the shields 412,...,415 for reducing or minimizing the field peak at the respective electrode 423/433/443 and/or shield 412,...,415. The electrodes 423/433/443 are connective by voltage connections, e.g. to a high voltage cascade.
Figure 10 shows the principle structure of an acceleration stage of a modular matt-ceramic tube wUh a modular hKHstep acceleration phase wittt two accotorotton modules 42/43 with ceramic insutatof 50. accokxalion electrodes 423/433 and voltage connections 421/431.
Figure 11 shows schematicaiy the potential dfetrtoution in a modular X-ray tube 10 according to the invention from an embodiment example with a • SOOkVtube.
Figure 12 shows schematically an irradiation system 60 with an X-ray tube 10 according to the invention. The irradiation system 60 comprises a high voltage cascade 62 for voltage supply of the X-ray tube 10, a high voltage transformer 63 as weN as an emission hole 61 for X-radiation y out of the shield housing 65.
Figure 13 shows a further embodiment variant of three acceleration modules 42/43/44 with ceramic insulator 50, electron shield 422/432/442 and acceleration electrodes 423/433/443.
Figure 4 to 10 Hlustrate architectures as they can be used to achieve the invention. In these embodiment examples for a modular X-ray tube 10, an
anode 20 and a cathode 30 are disposed opposite each other in a vacuumized inner space 40. The electrons e* are generated at the cathode 30, the cathode 30 serving as electron emitter. The cathode 30 thus serves the purpose, on the one hand, of generation of the electric field E, but, on the other hand, also the purpose of electron generation. Thus in principle all materials which can emit the electrons e* are suitable for this application. This process can be achieved through thermal emission, but also through field emission (cold emission). Used as cold emitters can be e.g. any kind of micro-tip arrays with usually diamond-like structures or e.g. also nano tubes. Of course cold emission can also be used with this tube type by using the Penning Effect on suitably formed metals. For instance, thermal emitters can be used that are also usable with this emitter concept, such as e.g. tungsten (W). lanthanum hexaboride (LaBe), dispenser cathodes (La in W) and/or oxide cathodes (e.g. ZrO). The electrons e* are accelerated to the anode 20 by means of impressible Ngh voltage, and generate Xrays yon a taigat surface of the anode 20. The anodes 20 fuMI two functions in the X-fay tubes 10. On the one hand they serve as positive electrode 20 for generation of an electric ReM E for acceleration of the electrons e. On the other hand, the anodes 20, or respectively the target roaterid enibedded to fte anodes 20. setv^
energy is converted into X-radtetion y. This conversion is, on the one hand, dependent on the particle energy, but also on the atomic number of the target material. In a first approximation, according to the Bethe formula, the energy loss of the particles is equal to the square of the atomic number Z of the target material
dW/ «Z2
With this process the anode 20 is thermally stressed. The anode or respectively the target material must therefore be able to withstand this thermal stress. It follows therefrom that the vapor pressure of the target material should be sufficiently low at operating temperature of the target in order not to influence in a negative way the vacuum necessary for operation of the X-ray tube 10. Thus target materials may preferably be used which are high-temperature-resistant or can be weN cooled. For this purpose the target material can be embedded in a good material capable of conducting heat (e.g.

copper), which is abte to be wed cooled, i.e. conducts heat well. For example, materials as heavy and temperature-resistant as possible can therefore be used as anode (target) 20. In particular, suitable therefor are e.g. materials such as tungsten (W, Z=74) and/or uranium (U, 2=92) and/or rhodium (Rh, Z=45) and/or silver (Ag, 2=47) and/or molybdenum (Mo, 2=42) and/or palladium (Pd, Z=46) and/or iron (Fe, 2=26) and/or copper (Cu, 2=29). In selecting the target material, it can be particularly advantageous, e.g. for analytical applications, to take into consideration that the characteristic lines are suitable for the specific application purpose.
The X-ray tube 10 further comprises a plurality of mutually complementary acceleration modules 41 ..... 45. Each acceleration module 41 ..... 45 comprises at least one potential-carrying electrode 20/30/423/433/443 with the corresponolng voltage connections 421/431/441 . A first acceleration module 41 comprises the cathode 30 with the electron generation e. i.e. with the etectoon emitter . A second •ccotoratton modute 45 comprises the anode 20 with toe X-radtaticNiY The X*ay tube comprises at toast one further accotoratton module 42,...,44 with a poterrtial-cariving electrode 423/433/443. aaiurnizedinriersp8»40(^
means of ceramic insulator 51. For the emissim concept accotcRng to Ihe invention, insulation materials can be used, for example, which satisfy the electric requirements of the X-ray tube 10 (field strength). For corresponding embodiment examples, the insulation materials should also be suitable for producing a metal-ceramic compound. In addition, the ceramic should be usable for high vacuum applications. Thus suitable materials are, for example, pure oxide ceramics, such as aluminum oxide, magnesium oxide, beryllium oxide and zirconium oxide. Also monocrystalline AfeOa (sapphire) is in principle suitable. Furthermore so-called glass ceramics, such as e.g. Macor®, or similar materials are conceivable. In particular, composite ceramics are of course also suitable (e.g. doped AfeOa), if they have the respective characteristics. The insulation ceramics 51 can be designed e.g. outwardly ridged, or in a similar way, in order to lengthen the insulation section of the insulation jacket 51 that is not vacuum-side, i.e. is situated in insulating oil. In the same way, however, any other design of the ceramic insulator 51, e.g. a pure cylindrical form, is conceivable, without affecting the core of the invention. The ceramic insulator
51 can have in addition e.g. a high-ohmic interior coating in order to divert possible charges which can be caused by various electronic processes, it being ensured at the same time that the acceleration voltage is able to be impressed. Figure 8 shows the principle structure of a modular metal-ceramic tube of two such further acceleration modules 42/43 with ceramic insulator 51, acceleration electrodes 423/433 and potential connections 421/431. The principle described here for construction of X-ray tubes 10, being composed e.g. of a metal-ceramic compound, can be series-connected according to the invention as often as desired, and can thus be used for acceleration of electrons e~ (multiphase acceleration). The last potential-carrying electrode of the acceleration structure is the anode 20, necessary for generation. On the other hand, the cathode 30, necessary for electron generation, represents the first electrode of the acceleration structure. This is shown in the embodiment examples of Figures 4 to 9. With suitable configuration and selection of the etectrodes, X-ray tubes 10 with a total energy c* up to 800 Wove* or ITIO^ RgureS). In contrast, conventional X-ray lubes untf now have been abte to be pio Electrons e* are thereby emitted from an electron emitter, i.e. a cathode 20, as a rule a hot tungsten coH, are accelerated toward a target through an impressed high voltage, X rays Y being radiated from the target, i.e. the anode 30, through a hole 301. Triple points (field peaks which lead to field emission of electrons e*) occur thereby both cathode-side as well as anode-side.
The difference in potential between each two potential-carrying electrodes 20/30/423/433/443 of adjacent acceleration modules 41 ,...,45 can be selected to be constant e.g. also for all acceleration modules 41,...,45, the final energy of the accelerated electrons e' being a whole number multiple of
the energy of an acceleration module 41 45. At least one of the acceleration
rrK>dules 41.....45 can furtfier apprise a re It is important to point out that with the X-ray tubes 10 according to the invention a modularity in principle exists, i.e. the increase in the radiance energy of an X-ray tube 10 can be achieved by adding one or more
acceleration segments 41 45 or acceleration modules 41 ,...,45. At least one
of the acceleration modules 41 ,...,45 can thereby be constructed such that it bears a rectosabte vacuum valve. The acceleration modules 41 ,...,45 can further comprise vacuum seals on one side or on both sides. This has the advantage that individual defective acceleration modules 41 ,...,45 can be simply replaced and/or recycled by a defective tube 10 being devacuumized using the rectosable vacuum valve 531, the defective acceleration module 41 ,...,45 being replaced by a new and/or functioning one, and the tube 10 being vacuumized again using a corresponding vacuum pump via the reclosable vacuum valve 531. It is also important to point out that the electrodes 20/30/423/433/443 of the acceleration modules 41,...,45 can comprise a shielding 412,. .,415 for suppression of the stray electron flow on the ceramic
insulator 51 (Figure 6/13). This has the advantage that the shields constitute supplementary protection for the ceramic insulators 51. The service life of the X-ray tubes and/or the difference in potential between the individual acceleration electrodes 20/30/423/433/443 can thereby be further increased. The simple and modular construction of the X-ray tube 10 according to the invention is especially well suited to a manufacturing process with a one-shot method, or respectively this design makes possible in principle the one-shot method in an efficient way. The soldering of the entire tube 10 takes place thereby in a one-step vacuum soldering process. This has the advantage, among others, that the subsequent evacuation of the X-ray tube 10 by means of high vacuum pump can be omitted. A further advantage of the one-shot method, i.e. of the one-step manufacturing process by means of the overall soldering of the tube in the vacuum (one-shot method), is. among others, that one has a single production process, and not three, as in the conventional way: 1. soldering off components / 2. joining of components (e.g. soldering or weldtog) / 3. evacuation of the tube by nteans of vacuum pump. The one-step manufacturing method is therefore eoo«iofnic^ more eMk^ent time-saving and cheaper. At the same time, with suitable process controi coritanfMnatkxi of the lubes can be minimized with this method. Anyhow it can be advantageous when toe tube is free of impurities to a targe extent which, as a nJe, minimize the ceramic insulator's ability to withstand voltage. Trie requirements with respect to vacuum tightness for the tubes 10 are in most cases the same with one-shot methods as with multi-step manufacturing processes. Since the fields inside the tube 10 are much smaller than in the case of conventional tubes, the tube 10 according to the invention is moreover less vulnerable to impurities and/or leaks. This makes the X-ray tube 10 according to the invention further suitable for the one-shot method. The X-ray tube 10 according to the invention can be excellently used for manufacture of an entire irradiation system and/or for individual irradiation devices 60 (see Figure 12). In such an irradiation device 60, the tube 10 can be stored in a housing 65, e.g. in insulating oil. The shield housing 65 can include an emission hole 61 for X-radiation Y- The irradiation device 60 comprises for the tube 10 a corresponding high voltage cascade 62, e.g. with an assigned high voltage transformer 63 and voltage connections 64 to the outside. Such irradiation devices 60 or monobtocks 60 can then be used e.g. for manufacture of larger Nraolation systems. Of course
it is dear to one skilled in the art in the field that the tube 10 according to the invention, without target or transmission anode, is also excellently suited as electron emitter and/or electron cannon with the corresponding industrial areas of application owing to its simple, modular construction and its high performance.
For the implementation according to the invention, it can be expedient for the shields 422/432/442 to be shaped such that the electron beam does not "see" any insulator surface 51 (Figure 13). Charging effects of the ceramic insulators 51 can result through impression of the acceleration voltage, which effects do not necessarily have to be caused by stray and secondary electron emission. By means of a geometry shown in Figure 13, or a simitar geometry, such charging effects can be prevented or diminished. A coating of the ceramic insulator can also be used in particular for feed of the potential, if e.g. a suitable conductive coaling is added outside on the insulatofs, so thoft the coaling ads as voltage UMcJoi. A suitable coaling against toe vacuumized inner space could also replace feemetaffc electrodes 423/433/443. TW8 would have ttte consequence, however, that one no longer rtasanyshtekftngasinFtgure 13. As an ernbocirnent example it would be possible e.g. to put a heical layer on the inner side (vacuum) of toe ceramic insulator 51 acting as voltage divider, and thus replacing the series of metallic electrodes 423/433/443.

WE CLAIM
1. An X-ray lube (10) in which an anode (20) and a eathode (30) are disposed opposite
each other in a vacuumizcd inner space (40), electrons (e) being able to be produced
at the cathode (30), being able to be accelerated to the anode (20) by means of
impressible high voltage, and X rays (y) being able to be produced at the anode (20)
by means of the electrons (c"), the X-ray tube (10) comprising a multiplicity of
mutually complementary acceleration modules (41,...,45), each acceleration module
(41,...,45) comprising at least one potential-carrying electrode (20/30/423/433/443),
a first acceleration module (41) comprising the cathode (30) with electron extraction
(e), and a second acceleration module (45) comprising the anode (20) with the X ray
generation (y), wherein
the X-ray tube (10) comprises at least one further acceleration module (42,...,44)
with a potential-carrying electrode (423/433/443), the acceleration module (42,.. .,44)
for acceleration of electrons (e) being repeatedly connectible in series as often as
desired, and the X-ray tube (10) being of modular construction.
2. 'fhe X-ray tube (10) as claimed in claim 1, wherein the difference in potential between each two potential-carrying electrodes (20/30/423/433/443) of adjacent acceleration modules (41,...,45) is constant for all acceleration modules (41,...,45), the final energy of the accelerated electrons (e") being a whole-number multiple of the energy of an acceleration module (41,...,45).
3. The X-ray tube (10) as claimed in claims 1 or 2, wherein at least one of the acceleration modules (41,...,45) has a reclosable vacuum valve (531) and/or vacuum seals on one side or on two sides.
4. The X-ray tube (10) as claimed in claims 1 to 3, wherein the acceleration modules (41,...,45) include a cylindrical ceramic insulator (53).

5. The X-ray tube (10) as claimed in claim 4, wherein the insulating ceramic (53) has a high-ohmic interior coating.
6. The X-ray tube (10) as claimed in claims 4 or 5, wherein the ceramic insulator (53) comprises a ridged exterior structure.
7. The X-ray tube (10) as claimed in claims 1 to 6, wherein the anode (20) comprises a target for X-ray generation as well as an emission hole (201) for X-radiation.
8. The X-ray tube (10) as claimed in claims 1 to 6, wherein the anode (20) includes a transmission anode, the transmission anode closing off the vacuumizcd inner space (40) toward the outside.
9. The X-ray tube (10) as claimed in claims 1 to 7, wherein the electrodes (20/30/423/433/443) of the acceleration modules (41,...,45) include a shield (412,...,415) for suppression of the stray electron flow on the ceramic insulator (51).
10. The X-ray tube (10) as claimed in claim 9, wherein at least one of the electrodes (423/433/443) and/or shields (412,...,415) comprises spherically or conically designed ends for reducing or minimizing the field peak at the respective electrode (423/433/443) and/or shield (412,...,415).
11. An irradiation system (60), wherein the irradiation system (60) comprises at least one X-ray tube (10) according to one of the claims 1 to 10 with a high voltage cascade (62) for voltage supply of the X-ray tube (10).
12. A method of production of an X-ray tube (10) according to one of the claims 1 to 10, wherein the X-ray tube (10) is produced in a one-step vacuum soldering process.

Documents:

2461-DELNP-2006-Correspondence Others-(02-09-2011).pdf

2961-delnp-2006-abstract.pdf

2961-delnp-2006-claims-(05-11-2012).pdf

2961-delnp-2006-Claims-(06-06-2011).pdf

2961-delnp-2006-Claims-(18-11-2010).pdf

2961-delnp-2006-claims.pdf

2961-DELNP-2006-Correspodence Others-(08-07-2011).pdf

2961-delnp-2006-Correspondence Others-(06-06-2011).pdf

2961-delnp-2006-Correspondence-IPO-(05-11-2012).pdf

2961-DELNP-2006-Correspondence-Others-(06-08-2010).pdf

2961-DELNP-2006-Correspondence-Others-(09-08-2010).pdf

2961-delnp-2006-Correspondence-Others-(18-11-2010).pdf

2961-DELNP-2006-Correspondence-Others-(27-10-2010).pdf

2961-delnp-2006-description (complete).pdf

2961-delnp-2006-Drawings-(18-11-2010).pdf

2961-delnp-2006-drawings.pdf

2961-delnp-2006-Form 3-(05-11-2012).pdf

2961-DELNP-2006-Form-1-(09-08-2010).pdf

2961-delnp-2006-form-1.pdf

2961-delnp-2006-form-2.pdf

2961-delnp-2006-Form-3-(06-06-2011).pdf

2961-delnp-2006-Form-3-(18-11-2010).pdf

2961-DELNP-2006-Form-3-(27-10-2010).pdf

2961-delnp-2006-form-3.pdf

2961-delnp-2006-form-5.pdf

2961-delnp-2006-GPA-(06-06-2011).pdf

2961-DELNP-2006-GPA-(09-08-2010).pdf

2961-delnp-2006-GPA-(18-11-2010).pdf

2961-delnp-2006-PA-(05-11-2012).pdf

2961-delnp-2006-pct-306.pdf

2961-delnp-2006-pct-search report.pdf

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Patent Number

261151

Indian Patent Application Number

2961/DELNP/2006

PG Journal Number

24/2014

Publication Date

13-Jun-2014

Grant Date

06-Jun-2014

Date of Filing

23-May-2006

Name of Patentee

COMET HOLDING AG

Applicant Address

HERRENGASSE 10,3175 FLAMATT SWITZERLAND

Inventors:

#	Inventor's Name	Inventor's Address
1	MILDNER MARK	ALTE MURTENSTRASSE 52A 3206 RIZENBACH SWITZERLAND
2	HOLM KURT	MARTINSBERGSTRASSE 49,5400 BADEN SWITZERLAND

PCT International Classification Number

A61L

PCT International Application Number

PCT/CH2003/000796

PCT International Filing date

2003-12-02

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	PCT/CH2003/000796	2003-12-02	Switzerland