EP1271602B1 - X-ray source having a liquid metal target - Google Patents

X-ray source having a liquid metal target Download PDF

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Publication number
EP1271602B1
EP1271602B1 EP02100714A EP02100714A EP1271602B1 EP 1271602 B1 EP1271602 B1 EP 1271602B1 EP 02100714 A EP02100714 A EP 02100714A EP 02100714 A EP02100714 A EP 02100714A EP 1271602 B1 EP1271602 B1 EP 1271602B1
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EP
European Patent Office
Prior art keywords
pressure
liquid metal
zone
arrangement
chamber
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EP02100714A
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German (de)
French (fr)
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EP1271602B8 (en
EP1271602A1 (en
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Geoffrey c/o Philips Corp Intel Prop GmbH Harding
Jens-Peter c/o Philips Cor Int Prop GmbH Schlomka
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Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
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Philips Intellectual Property and Standards GmbH
Koninklijke Philips Electronics NV
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H01J35/08—Anodes; Anti cathodes
    • H01J35/12—Cooling non-rotary anodes
    • H01J35/13—Active cooling, e.g. fluid flow, heat pipes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/08—Targets (anodes) and X-ray converters
    • H01J2235/081—Target material
    • H01J2235/082—Fluids, e.g. liquids, gases

Definitions

  • the invention relates to an arrangement for generating X-radiation upon impact of electrons with a liquid metal region, in which a liquid metal is arranged as X-ray target such that it can flow past an electron incident zone. Moreover, the invention relates to an X-ray source with an electron source for the emission of electrons and with such an arrangement for the generation of X-radiation. Finally, the invention also relates to an X-ray device with an X-ray detector and such an X-ray source.
  • Such an arrangement and such an X-ray source are known from US 6,185,277 B1.
  • the electrons emitted by an electron source enter through a thin window in the liquid metal and generate there X-radiation.
  • the liquid metal which has a high atomic number, circulates there under the action of a pump, so that the heat generated by the interaction with the electrons in the window and in the liquid metal can be dissipated.
  • the heat generated in this area is dissipated by a turbulent flow, which ensures effective cooling.
  • an X-ray source When used in a computed tomography scanner, an X-ray source is required which can deliver high pulse power of, for example, about 80 kW for only a short time of, for example, about 20 seconds.
  • high pulse power for example, about 80 kW
  • a lower power of, for example, about 30 kW is required, but must be supplied continuously, that is, for several hours.
  • the present invention is therefore based on the object to provide an arrangement for generating X-radiation with a liquid metal target, which can be used for various applications and manages with a relatively low pumping power for the liquid metal.
  • This object is achieved on the basis of the above-mentioned arrangement in that a separate from the liquid metal region pressure region is provided with a pressure medium such that by means of the pressure medium, a pressure on the liquid metal located in the liquid metal area for driving and passing the liquid metal at the Elektronenauf Economicszone is exercisable, wherein the pressure region has a rechargeable pressure accumulator for applying the pressure.
  • the liquid metal is not circulated by means of a pump as in the known X-ray source, but is only in a liquid metal region in which it can be reciprocated, but does not circulate.
  • a separate pressure area which also has a pressure accumulator in which energy can be stored, which is retrievable with the desired performance for moving the liquid metal in the liquid metal region, that is, for passing the liquid metal at the electron impact zone.
  • a recharging device for example a pump, which has a much lower power than the pump in the known X-ray source, since the energy in the pressure accumulator at any time, including in the operating pauses of the X-ray source, can be replenished, while in the known X-ray source, the pumping power must be made available in full during operation.
  • a reloading device can thus be made much more space-saving and cost-effective and allows a universal use of such an X-ray source.
  • the liquid metal region and the pressure region preferably adjoin one another at two locations, two so-called separation regions, in each of which a pressure can be exerted on the liquid metal by means of the pressure medium.
  • These separation areas can be configured, for example, as separation chambers, each with a liquid metal chamber and a pressure medium chamber, wherein the liquid metal and the pressure medium are separated by a flexible membrane, via which the pressure of the pressure medium can be transferred to the liquid metal. Depending on the set pressure ratio can thus both expand the liquid metal and the pressure medium into the respective separation chamber.
  • the separation regions could thus also be designed as cylinders, each with a movable piston, wherein the piston serves both as a release agent between the liquid metal and pressure medium and in principle can be designed drivable in any way.
  • a gas in particular air
  • the implementation of the accumulator that is, the storage of energy to exert pressure in retrievable form, can be solved in various ways.
  • using a gas as a pressure medium offers a gas pressure chamber which is closed off by controllable valves and whose pressure can be kept continuously at a certain level by means of a conventional pump.
  • control means For controlling the pressurization of the liquid metal and thus thus for determining the flow rate of the liquid metal in the electron impact zone, corresponding control means are provided, as indicated in claim 8.
  • These control means may in particular comprise the previously mentioned controllable valves, via which the pressure supply from the pressure accumulator to the liquid metal region, in particular to the separation regions, can be controlled.
  • the liquid metal region may have a constriction there.
  • This constriction can be designed asymmetrically on both sides of the electron impact zone, for example, to approximate the outer shape of a water drop, so that the flowing through the constriction liquid metal undergoes the lowest possible pressure loss.
  • the liquid metal is always in one Direction should flow through the constriction to achieve the maximum desired effect.
  • cooling means for example in the form of cooling channels running around the separation region, are arranged on at least one of the two separation regions, in which the liquid metal is preferably after an application phase.
  • the arrangement for generating X-radiation according to claim 1 is preferably part of an X-ray source having an electron source for emitting electrons, as specified in claim 12.
  • Such an X-ray source is preferably used together with an X-ray detector in an X-ray device, as specified in claim 13.
  • 1 denotes an electrically, preferably grounded, tubular envelope, which is closed off in a vacuum-tight manner through a window 5.
  • an electron source in the form of a cathode 3, which emits an electron beam 4 in the operating state, which passes through the window 5 on a liquid metal 9, which is in an inventive arrangement 2 for generating X-radiation.
  • Arrangement 2 essentially comprises a liquid metal region 7, in which a liquid metal 9 is located, onto which the electron beam 4 impinges in an electron incident zone 8.
  • a pressure region 10 Also located in the assembly 2 is a pressure region 10 through which pressure can be applied to the liquid metal 9 in the liquid metal region 7 to allow the liquid metal 9 to flow past the electron impact region 8 at a desired rate during operation.
  • FIG. 2 a shows the initial state of the arrangement 2 immediately before the start of operation
  • FIG. 2 b shows the operating state during operation
  • FIG. 2 c shows the final state after use
  • An exemplary dimensioning can provide a pressure of 200 bar in the pressure accumulator R3.
  • the pump 13 can then be configured as a gas compressor, which operates with a 50 Hz motor, a piston of 25 mm radius and a lifting height of 60 mm.
  • the pumping volume is therefore 118 cm 3 and the volume of compressed gas (at 200 bar) delivered per second is about 30 cm 3 .
  • the separation chambers R1 and R2 can be configured with a volume of 41 and can withstand a maximum pressure of 100 bar. These parameters require a radius of the separation chambers R1 and R2 of about 10 cm and a weight of about 3 kg.
  • the liquid metal used is preferably an alloy consisting of 35.6% Bi (eutectic), 22.9% Pb, 19.6% In and 21.9% Sn (in percent by weight).
  • the melting point of this alloy is then 56.5 ° C.
  • the separation chamber R1 is virtually empty and the separation chamber R2 practically full.
  • the liquid metal can then be in the Separation chamber R2 by means not shown heating elements at a temperature of about 65 ° C, ie in the liquid state, are held.
  • a first step (S1 in FIG. 3) it is ensured that the initial state shown in FIG. 2a is reached before the data acquisition begins.
  • the pressure P2 in the pressure chamber G2 of the separation chamber R2 is increased by a few bar, for example to 3 bar, so that the liquid metal completely flows out of the separation chamber R2 and collects completely in the separation chamber R1.
  • the valve V2 is slightly opened to bring a small pressure from the pressure accumulator R3 in the separation chamber R2.
  • the valve V1 is opened to the atmosphere, so that there is atmospheric pressure in the gas pressure chamber G1.
  • the valve V1 When the initial state shown in Figure 2a is reached, the valve V1 is opened to the accumulator R3 a few seconds before the start of the data acquisition, so that the pressure P1 in the gas pressure chamber G1 very quickly reaches the working pressure. Thereby, the liquid metal 9 completely located in the liquid metal chamber L1 of the separation chamber R1 is squeezed out of the separation chamber R1 by the influence of the pressure acting on the membrane M1 and flows at high speed through the restriction 8 in the electron incident region. In order to prevent possibly occurring due to the Bernoulli effect cavitations in the constriction 8, a back pressure P2 is preferably simultaneously generated in the gas pressure chamber G2 of the separation chamber R2.
  • valve V2 is also opened to the pressure accumulator R3 at the same time as the valve V1 is opened (step S2 in FIG. 3).
  • a pressure P2 in the separation chamber R2 for example, 20 bar (or less up to 1 bar) are set, so that there is a pressure difference P1-P2 of preferably 20 to 50 bar sets.
  • step S3 in FIG. 3 the X-ray emitter according to the invention is produced operated, the electron beam is thus turned on and it is generated X-rays.
  • the liquid metal 9 flows at the desired speed of, for example, 100 cm 3 / s for the duration of the data acquisition, for example 20 s at CT, from the separation chamber R1 into the separation chamber R2.
  • the valves V1 and V2 are continuously open (or fully or partially closed) to apply the required working pressure.
  • the pressure accumulator R3 must of course have sufficient capacity to maintain the high pressure P1, for example, 40 to 70 bar for a sufficient period of time, so that the liquid metal 9 sufficiently long and fast enough from the Separation chamber R1 flows into the separation chamber R2.
  • the pressure accumulator R3 has a volume of about 31 at a maximum pressure of 200 bar.
  • step S4 When the data acquisition is completed, the electron beam 4 is turned off and the valves V1 and V2 are opened to the atmosphere, so that the pressure P1 and P2 drops back to atmospheric pressure (step S4).
  • the liquid metal 9 is now largely or completely in the separation chamber R2, as shown in Figure 2c. Since the liquid metal 9 has heated due to the incident electrons 4 in the electron impact zone 8, cooling channels 14 are provided, with which the liquid metal 9 can be cooled in the separation chamber R2, preferably to a temperature of 60 to 65 ° C, so that the liquid metal 9 remains in a liquid state.
  • a final step (S5) it is also ensured by means of the pump 13 that the pressure in the pressure accumulator R3 is again “reloaded” so that sufficient pressure is again available for the next run.
  • the power of the pump 13 does not need to be turned off to the highest required power that must be provided during operation of the X-ray source, but must only be designed so that the pressure in the pressure accumulator R3 during the downtime again to a sufficiently high Pressure can be adjusted.
  • the pump must be designed with the known X-ray source for full operating performance.
  • the constriction 8 behind the window 5 is designed asymmetrically to extend to the separation chambers R 1 and R 2. This is intended to ensure that the pressure loss which the liquid metal 9 flowing from the separation chamber R1 to the separation chamber R2 undergoes the lowest possible pressure loss during operation and thus achieves the highest possible flow velocity in the electron impact zone.
  • the arrangement shown is thus only to operate so that the liquid metal 9 is always pressed during operation of the separation chamber R1 in the separation chamber R2.
  • the constriction 8 may also be designed symmetrically, and cooling channels 14 may also be provided around the separation chamber R1, so that the liquid metal 9 can be pressed in operation in both directions.

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • X-Ray Techniques (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)

Description

Die Erfindung betrifft eine Anordnung zur Erzeugung von Röntgenstrahlung beim Auftreffen von Elektronen mit einem Flüssigmetallbereich, in dem ein flüssiges Metall als Röntgentarget derart angeordnet ist, dass es an einer Elektronenauftreffzone vorbei fließen kann. Außerdem betrifft die Erfindung einen Röntgenstrahler mit einer Elektronenquelle zur Emission von Elektronen und mit einer solchen Anordnung zur Erzeugung von Röntgenstrahlung. Schließlich betrifft die Erfindung auch eine Röntgeneinrichtung mit einem Röntgendetektor und einem solchen Röntgenstrahler.The invention relates to an arrangement for generating X-radiation upon impact of electrons with a liquid metal region, in which a liquid metal is arranged as X-ray target such that it can flow past an electron incident zone. Moreover, the invention relates to an X-ray source with an electron source for the emission of electrons and with such an arrangement for the generation of X-radiation. Finally, the invention also relates to an X-ray device with an X-ray detector and such an X-ray source.

Eine solche Anordnung und ein solcher Röntgenstrahler sind aus der US 6,185,277 B1 bekannt. Dort treten die von einer Elektronenquelle emittierten Elektronen durch ein dünnes Fenster in das flüssige Metall ein und erzeugen dort Röntgenstrahlung. Das flüssige Metall, das eine hohe Ordnungszahl aufweist, zirkuliert dort unter der Wirkung einer Pumpe, so dass die durch die Wechselwirkung mit den Elektronen im Fenster und im flüssigen Metall erzeugte Wärme abgeführt werden kann. Die in diesem Bereich erzeugte Wärme wird durch eine turbulente Strömung abgeführt, was eine effektive Kühlung gewährleistet.Such an arrangement and such an X-ray source are known from US 6,185,277 B1. There, the electrons emitted by an electron source enter through a thin window in the liquid metal and generate there X-radiation. The liquid metal, which has a high atomic number, circulates there under the action of a pump, so that the heat generated by the interaction with the electrons in the window and in the liquid metal can be dissipated. The heat generated in this area is dissipated by a turbulent flow, which ensures effective cooling.

Es sind mehrere verschiedene Anwendungen denkbar, für die eine solche Anordnung zur Erzeugung von Röntgenstrahlung eingesetzt werden kann. Bei Einsatz in einem Computertomographen wird ein Röntgenstrahler benötigt, der eine hohe impulsförmige Leistung von beispielsweise etwa 80 kW für nur kurze Zeit von beispielsweise etwa 20 s liefern kann. Für eine andere Art von Anwendung in einer Röntgenanlage zur Gepäckuntersuchung, insbesondere auf Sprengstoff oder Drogen, wird dagegen nur eine niedrigere Leistung von beispielsweise etwa 30 kW benötigt, die jedoch kontinuierlich, das heißt für mehrere Stunden, geliefert werden muss.Several different applications are conceivable for which such an arrangement can be used to generate X-radiation. When used in a computed tomography scanner, an X-ray source is required which can deliver high pulse power of, for example, about 80 kW for only a short time of, for example, about 20 seconds. For a different type of application in an X-ray system for baggage inspection, especially on explosives or drugs, however, only a lower power of, for example, about 30 kW is required, but must be supplied continuously, that is, for several hours.

Bei dem bekannten Röntgenstrahler mit einem Flüssigmetall-Target, bei dem das flüssige Metall mittels einer Pumpe zirkuliert wird, wurde bislang stets davon ausgegangen, dass mittels einer einzigen Pumpe die beschriebenen Erfordernisse erfüllt werden können. Es wurde jedoch festgestellt, dass bei der ersten Art von Anwendung, in der Computertomographie, zwar die erforderliche impulsförmige Leistung sehr hoch ist, die durchschnittliche Leistung jedoch viel niedriger liegt. Wenn davon ausgegangen wird, dass typischerweise jeder Einsatzzeit von etwa 20 s eine Verweilzeit von etwa 80 s folgt, dann liegt die durchschnittliche elektrische Leistung bei (80 kW·20 s)/(80 s+20 s)=16 kW. Demnach müsste es auch möglich sein, die Leistung der Pumpe entsprechend zu verringern, die Pumpe also nicht für die maximale impulsförmige Leistung von 80 kW, sondern nur für die durchschnittlich benötigte Leistung von etwa 16 kW auszulegen, was eine starke Platz- und Kostenersparnis zur Folge hätte.In the known X-ray source with a liquid metal target in which the liquid metal is circulated by means of a pump, it has hitherto always been assumed that the requirements described can be met by means of a single pump. It was however, it has been found that in the first type of application, computed tomography, although the required pulse power is very high, the average power is much lower. Assuming that typically every 20 s deployment time is followed by a residence time of about 80 s, the average electrical power is (80 kW * 20 s) / (80 s + 20 s) = 16 kW. Accordingly, it would also be possible to reduce the power of the pump accordingly, so the pump is not designed for the maximum pulse-shaped power of 80 kW, but only for the average required power of about 16 kW, resulting in a strong space and cost savings would have.

Der vorliegenden Erfindung liegt deshalb die Aufgabe zugrunde, eine Anordnung zur Erzeugung von Röntgenstrahlung mit einem Flüssigmetall-Target zu schaffen, die für verschiedene Anwendungen einsetzbar ist und mit einer verhältnismäßig geringen Pumpleistung für das Flüssigmetall auskommt. Diese Aufgabe wird ausgehend von der eingangs genannten Anordnung dadurch gelöst, dass ein von dem Flüssigmetallbereich getrennter Druckbereich mit einem Druckmittel vorgesehen ist derart, dass mittels des Druckmittels ein Druck auf das in dem Flüssigmetallbereich befindliche flüssige Metall zum Antreiben und Vorbeiführen des flüssigen Metalls an der Elektronenauftreffzone ausübbar ist, wobei der Druckbereich einen wiederaufladbaren Druckspeicher zum Aufbringen des Drucks aufweist.The present invention is therefore based on the object to provide an arrangement for generating X-radiation with a liquid metal target, which can be used for various applications and manages with a relatively low pumping power for the liquid metal. This object is achieved on the basis of the above-mentioned arrangement in that a separate from the liquid metal region pressure region is provided with a pressure medium such that by means of the pressure medium, a pressure on the liquid metal located in the liquid metal area for driving and passing the liquid metal at the Elektronenauftreffzone is exercisable, wherein the pressure region has a rechargeable pressure accumulator for applying the pressure.

Erfindungsgemäß wurde erkannt, dass die erforderliche Pumpleistung zum Vorbeiführen des flüssigen Metalls an der Elektronenauftreffzone nicht entsprechend der höchsten elektrischen (pulsförmigen) Leistung ausgelegt werden muss, sondern dass die erforderliche Pumpleistung auf die durchschnittliche geforderte elektrische Leistung abgestellt werden kann, wenn ergänzende Mittel zur Speicherung von Pumpleistung vorgesehen werden. Unter der Annahme, dass die Energie, die benötigt wird, um ein Flüssigkeitsvolumen V durch eine Druckdifferenz von ΔP zu bewegen, gleich V·ΔP ist, dann erfordert die Pumpe eine Leistung von 1/ε·(V·ΔP)/T. Durch ε wird dabei berücksichtigt, dass die Umwandlung von mechanischer Energie in hydrodynamische Energie einen Wirkungsgrad von weniger als 100% aufweist; T ist die Zeitdauer, über die die Energieübertragung auf das flüssige Metall verteilt werden kann. Die Pumpleistung kann also signifikant reduziert werden, indem die Energiezufuhr in Form von Pumpenergie über 100 s (im oben beschriebenen Beispiel der Computertomographie) verteilt wird, anstatt auf nur 20 s konzentriert zu werden. Erfindungsgemäß müssen also die folgenden Bedingungen erfüllt werden:

  • a) Die Energie, die das flüssige Metall antreiben wird, kann effektiv gespeichert werden, ist nachlieferbar und kann bei Bedarf in kurzer Zeit abgerufen werden;
  • b) die Art der Energiespeicherung ist kompatibel mit dem Erfordernis, dass das flüssige Metall nach Art einer Pumpe angetrieben werden muss.
According to the invention, it has been recognized that the required pumping power for passing the liquid metal at the electron impaction zone does not have to be designed according to the highest electrical (pulse) power, but that the required pumping power can be adjusted to the average required electrical power if supplementary means for the storage of Pumping power to be provided. Assuming that the energy needed to move a liquid volume V through a pressure difference of ΔP is equal to V · ΔP, then the pump requires a power of 1 / ε · (V · ΔP) / T. By ε is taken into account that the conversion of mechanical energy into hydrodynamic energy has an efficiency of less than 100%; T is the period of time over which the energy transfer can be distributed to the liquid metal. The pumping power can thus be significantly reduced by the Energy supply in the form of pump energy over 100 s (in the example of computed tomography described above) is distributed, instead of being concentrated on only 20 s. According to the invention, therefore, the following conditions must be met:
  • a) The energy that will drive the liquid metal can be stored effectively, is re-deliverable and can be retrieved as needed in a short time;
  • b) the type of energy storage is compatible with the requirement that the liquid metal must be driven in the manner of a pump.

Erfindungsgemäß wird dies dadurch erreicht, dass das flüssige Metall nicht wie bei dem bekannten Röntgenstrahler mittels einer Pumpe zirkuliert wird, sondern sich nur in einem Flüssigmetallbereich befindet, in dem es hin- und herbewegt werden kann, jedoch nicht zirkuliert. Weiter ist ein davon getrennter Druckbereich vorgesehen, der auch einen Druckspeicher aufweist, in dem Energie gespeichert werden kann, die zum Bewegen des flüssigen Metalls in dem Flüssigmetallbereich, das heißt zum Vorbeiführen des flüssigen Metalls an der Elektronenauftreffzone, mit der gewünschten Leistung abrufbar ist. Um den Druckspeicher wieder aufzuladen, also wieder Energie nachzuführen, kann hier eine Nachladevorrichtung, beispielsweise eine Pumpe, vorgesehen sein, die eine wesentlich geringere Leistung aufweist, als die Pumpe bei dem bekannten Röntgenstrahler, da hier die Energie in den Druckspeicher jederzeit, also auch in den Betriebspausen des Röntgenstrahlers, nachgeliefert werden kann, während bei dem bekannten Röntgenstrahler die Pumpleistung in voller Höhe beim Betrieb zur Verfügung gestellt werden muss. Eine solche Nachladevorrichtung kann also wesentlich platzsparender und kostengünstiger ausgestaltet werden und erlaubt einen universellen Einsatz eines solchen Röntgenstrahlers.According to the invention this is achieved in that the liquid metal is not circulated by means of a pump as in the known X-ray source, but is only in a liquid metal region in which it can be reciprocated, but does not circulate. Further, there is provided a separate pressure area, which also has a pressure accumulator in which energy can be stored, which is retrievable with the desired performance for moving the liquid metal in the liquid metal region, that is, for passing the liquid metal at the electron impact zone. In order to recharge the pressure accumulator, ie to re-energize, a recharging device, for example a pump, may be provided, which has a much lower power than the pump in the known X-ray source, since the energy in the pressure accumulator at any time, including in the operating pauses of the X-ray source, can be replenished, while in the known X-ray source, the pumping power must be made available in full during operation. Such a reloading device can thus be made much more space-saving and cost-effective and allows a universal use of such an X-ray source.

Vorzugsweise grenzen der Flüssigmetallbereich und der Druckbereich an zwei Stellen, zwei sogenannten Trennbereichen, aneinander, in denen jeweils mittels des Druckmittels ein Druck auf das flüssige Metall ausgeübt werden kann. Diese Trennbereiche können beispielsweise als Trennkammern mit jeweils einer Flüssigmetallkammer und einer Druckmittelkammer ausgestaltet sein, wobei das flüssige Metall und das Druckmittel durch eine flexible Membran getrennt sind, über die der Druck von dem Druckmittel auf das flüssige Metall übertragen werden kann. Je nach eingestelltem Druckverhältnis kann sich somit sowohl das flüssige Metall als auch das Druckmittel in die jeweilige Trennkammer hinein ausdehnen.The liquid metal region and the pressure region preferably adjoin one another at two locations, two so-called separation regions, in each of which a pressure can be exerted on the liquid metal by means of the pressure medium. These separation areas can be configured, for example, as separation chambers, each with a liquid metal chamber and a pressure medium chamber, wherein the liquid metal and the pressure medium are separated by a flexible membrane, via which the pressure of the pressure medium can be transferred to the liquid metal. Depending on the set pressure ratio can thus both expand the liquid metal and the pressure medium into the respective separation chamber.

Es sind noch weitere alternative Lösungen für die Ausgestaltung des Flüssigmetallbereichs und des Druckbereichs denkbar. Diese haben jedoch alle gemeinsam, dass über das Druckmittel indirekt ein Druck auf das flüssige Metall in dem Flüssigmetallbereich ausgeübt wird, so dass das flüssige Metall also nicht direkt angetrieben wind. Die Trennbereiche könnten somit auch als Zylinder mit jeweils einem verfahrbaren Kolben ausgestaltet sein, wobei der Kolben sowohl als Trennmittel zwischen flüssigem Metall und Druckmittel dient und grundsätzlich auf beliebige Weise antreibbar ausgestaltet sein kann.There are still other alternative solutions for the design of the liquid metal region and the pressure range conceivable. However, these all have in common that pressure indirectly exerted on the liquid metal in the liquid metal region via the pressure medium, so that the liquid metal so not directly driven wind. The separation regions could thus also be designed as cylinders, each with a movable piston, wherein the piston serves both as a release agent between the liquid metal and pressure medium and in principle can be designed drivable in any way.

Verschiedene Ausgestaltungen für das Druckmittel sind in den Ansprüchen 5 bis 7 angegeben, wobei vorzugsweise als Druckmittel ein Gas, insbesondere Luft, verwendet wird. Auch die Umsetzung des Druckspeichers, das heißt die Speicherung von Energie zur Ausübung eines Drucks in abrufbarer Form, kann auf verschiedene Weise gelöst werden. Unter Verwendung eines Gases als Druckmittel bietet sich insbesondere eine Gasdruckkammer an, die durch steuerbare Ventile abgeschlossen ist und deren Druck mittels einer konventionellen Pumpe kontinuierlich auf einem bestimmten Level gehalten werden kann.Various embodiments of the pressure medium are specified in claims 5 to 7, wherein preferably as a pressure medium, a gas, in particular air, is used. The implementation of the accumulator, that is, the storage of energy to exert pressure in retrievable form, can be solved in various ways. In particular, using a gas as a pressure medium offers a gas pressure chamber which is closed off by controllable valves and whose pressure can be kept continuously at a certain level by means of a conventional pump.

Zur Steuerung der Druckbeaufschlagung des flüssigen Metalls und damit also zur Bestimmung der Fließgeschwindigkeit des flüssigen Metalls in der Elektronenauftreffzone sind entsprechende Steuermittel vorgesehen, wie sie in Anspruch 8 angegeben sind. Diese Steuermittel können insbesondere die bereits angesprochenen steuerbaren Ventile aufweisen, über die die Druckzufuhr von dem Druckspeicher zu dem Flüssigmetallbereich, insbesondere zu den Trennbereichen, gesteuert werden kann.For controlling the pressurization of the liquid metal and thus thus for determining the flow rate of the liquid metal in the electron impact zone, corresponding control means are provided, as indicated in claim 8. These control means may in particular comprise the previously mentioned controllable valves, via which the pressure supply from the pressure accumulator to the liquid metal region, in particular to the separation regions, can be controlled.

Um eine möglichst hohe Fließgeschwindigkeit in der Elektronenauftreffzone zu erreichen, kann der Flüssigmetallbereich dort eine Verengung aufweisen. Diese Verengung kann zu beiden Seiten der Elektronenauftreffzone asymmetrisch ausgestaltet sein, beispielsweise der äußeren Form eines Wassertropfens angenähert sein, damit das durch die Verengung hindurchfließende flüssige Metall einen möglichst geringen Druckverlust erfährt. Zu berücksichtigen ist dann jedoch, dass im Betrieb das flüssige Metall immer nur in einer Richtung durch die Verengung hindurchfließen sollte, um die größtmögliche gewünschte Wirkung zu erzielen.In order to achieve the highest possible flow velocity in the electron impact zone, the liquid metal region may have a constriction there. This constriction can be designed asymmetrically on both sides of the electron impact zone, for example, to approximate the outer shape of a water drop, so that the flowing through the constriction liquid metal undergoes the lowest possible pressure loss. However, it should be remembered that in operation, the liquid metal is always in one Direction should flow through the constriction to achieve the maximum desired effect.

Im Betrieb wird das flüssige Metall um bis zu einige 100 °C erhitzt. Zur Kühlung des aufgeheizten flüssigen Metalls sind deshalb an mindestens einem der beiden Trennbereiche, in dem sich bevorzugt nach einer Einsatzphase das flüssige Metall befindet, Kühlmittel, beispielsweise in Form von um den Trennbereich herumlaufenden Kühlkanälen, angeordnet.In operation, the liquid metal is heated up to several 100 ° C. For cooling the heated liquid metal, therefore, cooling means, for example in the form of cooling channels running around the separation region, are arranged on at least one of the two separation regions, in which the liquid metal is preferably after an application phase.

Die Anordnung zur Erzeugung von Röntgenstrahlung gemäß Anspruch 1 ist bevorzugt Teil eines Röntgenstrahlers mit einer Elektronenquelle zur Emission von Elektronen, wie in Anspruch 12 angegeben ist. Ein solcher Röntgenstrahler wird bevorzugt zusammen mit einem Röntgendetektor in einer Röntgeneinrichtung eingesetzt, wie sie in Anspruch 13 angegeben ist.The arrangement for generating X-radiation according to claim 1 is preferably part of an X-ray source having an electron source for emitting electrons, as specified in claim 12. Such an X-ray source is preferably used together with an X-ray detector in an X-ray device, as specified in claim 13.

Die Erfindung wird nachfolgend anhand der Zeichnungen näher erläutert. Es zeigen:

Figur 1
eine schematische Darstellung eines erfindungsgemäßen Röntgenstrahlers,
Figur 2a bis 2c
schematische Darstellungen einer erfindungsgemäßen Anordnung zur Erzeugung von Röntgenstrahlung in verschiedenen Betriebszuständen und
Figur 3
ein Ablaufdiagramm zur Erläuterung der verschiedenen Betriebszustände einer erfindungsgemäßen Anordnung zur Erzeugung von Röntgenstrahlung.
The invention will be explained in more detail with reference to the drawings. Show it:
FIG. 1
a schematic representation of an X-ray source according to the invention,
FIGS. 2a to 2c
schematic representations of an inventive arrangement for generating X-radiation in different operating conditions and
FIG. 3
a flowchart for explaining the various operating states of an inventive arrangement for generating X-radiation.

Bei dem in Figur 1 schematisch gezeigten erfindungsgemäßen Röntgenstrahler bezeichnet 1 einen elektrisch, vorzugsweise geerdeten, Röhrenkolben, der durch ein Fenster 5 vakuumdicht abgeschlossen ist. In dem Vakuumraum des Röhrenkolbens befindet sich eine Elektronenquelle in Form einer Kathode 3, die im Betriebszustand einen Elektronenstrahl 4 emittiert, der durch das Fenster 5 hindurch auf ein flüssiges Metall 9 trifft, das sich in einer erfindungsgemäßen Anordnung 2 zur Erzeugung von Röntgenstrahlung befindet. Diese Anordnung 2 umfasst im Wesentlichen einen Flüssigmetallbereich 7, in dem sich ein flüssiges Metall 9 befindet, auf das in eine Elektronenauftreffzone 8 der Elektronenstrahl 4 auftrifft. Weiter befindet sich in der Anordnung 2 ein Druckbereich 10, über den ein Druck auf das flüssige Metall 9 in dem Flüssigmetallbereich 7 ausgeübt werden kann, damit das flüssige Metall 9 an der Elektronenauftreffzone 8 während des Betriebes mit einer gewünschten Geschwindigkeit vorbeiströmt.In the X-ray emitter according to the invention shown schematically in Figure 1, 1 denotes an electrically, preferably grounded, tubular envelope, which is closed off in a vacuum-tight manner through a window 5. In the vacuum space of the tube piston is an electron source in the form of a cathode 3, which emits an electron beam 4 in the operating state, which passes through the window 5 on a liquid metal 9, which is in an inventive arrangement 2 for generating X-radiation. These Arrangement 2 essentially comprises a liquid metal region 7, in which a liquid metal 9 is located, onto which the electron beam 4 impinges in an electron incident zone 8. Also located in the assembly 2 is a pressure region 10 through which pressure can be applied to the liquid metal 9 in the liquid metal region 7 to allow the liquid metal 9 to flow past the electron impact region 8 at a desired rate during operation.

Durch die Wechselwirkung der durch das Fenster 5 hindurchtretenden Elektronen 4 mit dem flüssigen Metall 9 entsteht Röntgenstrahlung, die durch das Fenster 5 und ein Röntgenstrahlen-Austrittsfenster 6 im Röhrenkolben 1 hindurch austritt. Das flüssige Metall 9 dient somit als Röntgentarget. Hinsichtlich der weiteren Ausgestaltung des gezeigten Röntgenstrahlers, insbesondere des Elektronenstrahls 4, des Fensters 5 und des flüssigen Metalls 9, sei auf die bereits genannte Druckschrift US 6,185,277 B1 verwiesen, deren diesbezügliche Ausrührungen für den vorliegenden Röntgenstrahler gleichermaßen Gültigkeit haben und hiermit als in die vorliegende Anmeldung mit aufgenommen gelten.As a result of the interaction of the electrons 4 passing through the window 5 with the liquid metal 9, X-ray radiation emerges, which exits through the window 5 and an X-ray exit window 6 in the tube piston 1. The liquid metal 9 thus serves as an X-ray target. With regard to the further embodiment of the X-ray source shown, in particular the electron beam 4, the window 5 and the liquid metal 9, reference is made to the already mentioned document US 6,185,277 B1, their respective Ausrührungen for the present X-ray source are equally valid and hereby as in the present application apply with recorded.

In den Figuren 2a bis 2c ist die Anordnung 2 schematisch und in verschiedenen Betriebszuständen näher dargestellt. Figur 2a zeigt zunächst den Ausgangszustand der Anordnung 2 unmittelbar vor Betriebsbeginn, Figur 2b zeigt den Betriebszustand während des Betriebes und Figur 2c zeigt den Endzustand nach einem EinsatzIn the figures 2a to 2c, the arrangement 2 is shown schematically and in various operating states closer. FIG. 2 a shows the initial state of the arrangement 2 immediately before the start of operation, FIG. 2 b shows the operating state during operation, and FIG. 2 c shows the final state after use

Wie aus den Figuren zu erkennen ist, ist der Flüssigmetallbereich 7, in dem sich das flüssige Metall 9 befindet, als längliche Röhre ausgsstaltet. Diese Röhre weist in der Elektronenauftreffzone 8, also in dem Bereich hinter dem Fenster 5, eine Verengung auf. Außerdem weiten sich die beiden Enden des röhrenförmigen Flüssigmetallbereichs 7 zu Trennkammern R1 und R2 auf. Diese Trennkammern beinhalten jeweils eine flexible Membran M1, M2, die die Trennkammern R1, R2 in jeweils eine Flüssigmetallkammer L1, L2 und eine Druckkammer G1, G2 (siehe Figur 2b) unterteilen. Die Druckkammern G1, G2 sind dabei bereits Teil des Druckbereichs 10, in dem sich ein Druckmittel 11 befindet, bei der vorliegenden Ausgestaltung beispielsweise ein Gas wie insbesondere Luft. Dieser Druckbereich 10 ist ebenfalls im Wesentlichen röhrenförmig ausgebildet, wobei sich die beiden Enden zu den genannten Druckkammern G1, G2 aufweiten. Zusätzlich ist innerhalb des röhrenförmigen Druckbereichs 10 ein Druckspeicher R3, vorliegend in Form einer Druckkammer, vorgesehen, in dem ein hoher Druck vorrätig gehalten werden kann. Dazu wird mittels einer Pumpe 13 ein Gas 12, beispielsweise Luft, in die Druckkammer R3 gepumpt, bis dort ein gewünschter hoher Druck vorhanden ist.
Zwischen der Druckkammer R3 und den beiden Trennkammern R1 und R2 ist weiter jeweils ein von einer Steuereinrichtung 15 gesteuertes Ventil V1, V2 angeordnet, über die zu gewünschten Zeitpunkten ein Druck gewünschter Höhe auf die Membranen M1 und M2 ausgeübt werden kann. Insbesondere können die Ventile V1 und V2 als computergesteuerte Ventile ausgestaltet sein, die im Wesentlichen drei verschiedene Funktionen bzw. Stellungen aufweisen müssen:

  • a) sie sind geschlossen, um einen Gasfluss zu verhindern;
  • b) sie sind geöffnet, um einen Gasfluss zu ermöglichen;
  • c) sie müssen einen Gasfluss in verschiedenen Richtungen ermöglichen, insbesondere von dem Druckspeicher R3 zu den Trennkammern R1 und R2 (mit gewünschter Druckhöhe) und von den Trennkammern R1 und R2 in die Umgebung, um den Druck in den Trennkammern R1 und R2 zu erniedrigen.
As can be seen from the figures, the liquid metal region 7, in which the liquid metal 9 is located, is configured as an elongate tube. This tube has a constriction in the electron impact zone 8, ie in the area behind the window 5. In addition, the two ends of the tubular liquid metal portion 7 expand to separation chambers R1 and R2. These separation chambers each contain a flexible membrane M1, M2, which divide the separation chambers R1, R2 into a respective liquid metal chamber L1, L2 and a pressure chamber G1, G2 (see FIG. 2b). The pressure chambers G1, G2 are already part of the pressure range 10, in which a pressure medium 11 is located, in the present embodiment, for example, a gas such as air in particular. This pressure region 10 is also substantially tubular, with the two ends to expand said pressure chambers G1, G2. In addition, within the tubular pressure region 10, a pressure accumulator R3, in the present case in the form of a pressure chamber, is provided, in which a high pressure can be kept in stock. For this purpose, by means of a pump 13, a gas 12, for example air, is pumped into the pressure chamber R3 until a desired high pressure is present there.
Between the pressure chamber R3 and the two separation chambers R1 and R2, a valve V1, V2 controlled by a control device 15 is further arranged, via which a pressure of desired height can be exerted on the membranes M1 and M2 at desired times. In particular, the valves V1 and V2 can be designed as computer-controlled valves which essentially have to have three different functions or positions:
  • a) they are closed to prevent gas flow;
  • b) they are open to allow gas flow;
  • c) they must allow a gas flow in different directions, in particular from the pressure accumulator R3 to the separation chambers R1 and R2 (with desired pressure level) and from the separation chambers R1 and R2 in the environment to lower the pressure in the separation chambers R1 and R2.

Eine beispielhafte Dimensionierung kann einen Druck in Höhe von 200 bar in dem Druckspeicher R3 vorsehen. Die Pumpe 13 kann dann als Gaskompressor ausgestaltet sein, der mit einem 50 Hz-Motor arbeitet, einen Kolben von 25 mm Radius und eine Hubhöhe von 60 mm aufweist. Das Pumpvolumen ist demnach 118 cm3 und das Volumen an komprimiertem Gas (bei 200 bar), das pro Sekunde geliefert wird, ist etwa 30 cm3. Die Trennkammern R1 und R2 können mit einem Volumen von jeweils 41 ausgestaltet sein und einen Druck von maximal 100 bar aushalten. Diese Parameter erfordern einen Radius der Trennkammern R1 und R2 von etwa 10 cm und ein Gewicht von etwa 3 kg.An exemplary dimensioning can provide a pressure of 200 bar in the pressure accumulator R3. The pump 13 can then be configured as a gas compressor, which operates with a 50 Hz motor, a piston of 25 mm radius and a lifting height of 60 mm. The pumping volume is therefore 118 cm 3 and the volume of compressed gas (at 200 bar) delivered per second is about 30 cm 3 . The separation chambers R1 and R2 can be configured with a volume of 41 and can withstand a maximum pressure of 100 bar. These parameters require a radius of the separation chambers R1 and R2 of about 10 cm and a weight of about 3 kg.

Als flüssiges Metall wird vorzugsweise eine Legierung bestehend aus 35,6% Bi (eutektisch), 22,9% Pb, 19,6% In und 21,9% Sn verwendet (Angaben in Gewichtsprozent). Der Schmelzpunkt dieser Legierung liegt dann bei 56,5 °C. Bei dem in Figur 2a gezeigten Ausgangszustand, wenn der Röntgenstrahler also inaktiv ist, ist die Trennkammer R1 praktisch leer und die Trennkammer R2 praktisch voll. Das flüssige Metall kann dann in der Trennkammer R2 mittels nicht gezeigter Heizelemente auf einer Temperatur von etwa 65 °C, also in flüssigem Zustand, gehalten werden.The liquid metal used is preferably an alloy consisting of 35.6% Bi (eutectic), 22.9% Pb, 19.6% In and 21.9% Sn (in percent by weight). The melting point of this alloy is then 56.5 ° C. In the initial state shown in Figure 2a, when the X-ray source is therefore inactive, the separation chamber R1 is virtually empty and the separation chamber R2 practically full. The liquid metal can then be in the Separation chamber R2 by means not shown heating elements at a temperature of about 65 ° C, ie in the liquid state, are held.

Nachfolgend sollen nun die verschiedenen Betriebszustände, wie sie in den Figuren 2a bis 2c gezeigt sind und wie sie auch in dem Ablaufdiagramm in Figur 3 aufgeführt sind, näher erläutert werden, wobei angenommen wird, dass der erfindungsgemäße Röntgenstrahler in einem Computertomographen zur Datenerfassung eingesetzt wird. Zunächst wird in einem ersten Schritt (S1 in Figur 3) sichergestellt, dass der in Figur 2a gezeigte Ausgangszustand erreicht wird, bevor die Datenerfassung beginnt. Dazu wird der Druck P2 in der Druckkammer G2 der Trennkammer R2 um einige bar, beispielsweise auf 3 bar, erhöht, so dass das flüssige Metall aus der Trennkammer R2 vollständig herausfließt und sich in der Trennkammer R1 vollständig sammelt. Dazu wird das Ventil V2 leicht geöffnet, um einen geringen Druck aus dem Druckspeicher R3 in die Trennkammer R2 einzubringen. Das Ventil V1 wird dagegen zur Umgebung geöffnet, so dass in der Gasdruckkammer G1 Atmosphärendruck herrscht.Below, the various operating states, as shown in FIGS. 2a to 2c and as they are also listed in the flowchart in FIG. 3, will now be explained in more detail, it being assumed that the X-ray emitter according to the invention is used in a computer tomograph for data acquisition. First, in a first step (S1 in FIG. 3) it is ensured that the initial state shown in FIG. 2a is reached before the data acquisition begins. For this purpose, the pressure P2 in the pressure chamber G2 of the separation chamber R2 is increased by a few bar, for example to 3 bar, so that the liquid metal completely flows out of the separation chamber R2 and collects completely in the separation chamber R1. For this purpose, the valve V2 is slightly opened to bring a small pressure from the pressure accumulator R3 in the separation chamber R2. On the other hand, the valve V1 is opened to the atmosphere, so that there is atmospheric pressure in the gas pressure chamber G1.

Wenn der in Figur 2a gezeigte Ausgangszustand erreicht ist, wird wenigs Sekunden vor Beginn der Datenerfassung das Ventil V1 zum Druckspeicher R3 hin geöffnet, so dass der Druck P1 in der Gasdruckkammer G1 sehr schnell den Arbeitsdruck erreicht. Dadurch wird das flüssige Metall 9, das sich vollständig in der Flüssigmetallkammer L1 der Trennkammer R1 befindet, durch den Einfluss des Druckes, der auf die Membran M1 einwirkt, aus der Trennkammer R1 herausgepresst und fließt mit hoher Geschwindigkeit durch die Verengung 8 in der Elektronenauftreffzone. Um dabei möglicherweise aufgrund des Bernoulli-Effekts auftretende Kavitationen in der Verengung 8 zu verhindern, wird bevorzugt gleichzeitig ein Gegendruck P2 in der Gasdruckkammer G2 der Trennkammer R2 erzeugt. Dazu wird gleichzeitig mit Öffnen des Ventils V1 auch das Ventil V2 zum Druckspeicher R3 hin geöffnet (Schritt S2 in Figur 3). Somit kann beispielsweise für den Druck P1 in der Trennkammer R1 von 40 bis 70 bar, vorzugsweise 50 bar, und ein Druck P2 in der Trennkammer R2 von beispielsweise 20 bar (oder auch geringer bis zu 1 bar) eingestellt werden, so dass sich eine Druckdifferenz P1-P2 von vorzugsweise 20 bis 50 bar einstellt.When the initial state shown in Figure 2a is reached, the valve V1 is opened to the accumulator R3 a few seconds before the start of the data acquisition, so that the pressure P1 in the gas pressure chamber G1 very quickly reaches the working pressure. Thereby, the liquid metal 9 completely located in the liquid metal chamber L1 of the separation chamber R1 is squeezed out of the separation chamber R1 by the influence of the pressure acting on the membrane M1 and flows at high speed through the restriction 8 in the electron incident region. In order to prevent possibly occurring due to the Bernoulli effect cavitations in the constriction 8, a back pressure P2 is preferably simultaneously generated in the gas pressure chamber G2 of the separation chamber R2. For this purpose, the valve V2 is also opened to the pressure accumulator R3 at the same time as the valve V1 is opened (step S2 in FIG. 3). Thus, for example, for the pressure P1 in the separation chamber R1 of 40 to 70 bar, preferably 50 bar, and a pressure P2 in the separation chamber R2, for example, 20 bar (or less up to 1 bar) are set, so that there is a pressure difference P1-P2 of preferably 20 to 50 bar sets.

In diesem Betriebszustand (Schritt S3 in Figur 3) wird der erfindungsgemäße Röntgenstrahler betrieben, der Elektronenstrahl ist somit eingeschaltet und es wird Röntgenstrahlung erzeugt. Das flüssige Metall 9 fließt dabei mit der gewünschten Geschwindigkeit von beispielsweise 100 cm3/s für die Dauer der Datenerfassung, beispielsweise 20 s bei CT, von der Trennkammer R1 in die Trennkammer R2. Die Ventile V1 und V2 sind dabei kontinuierlich geöffnet (oder voll oder teilweise geschlossen) um den erforderlichen Arbeitsdruck aufzubringen. Der Druckspeicher R3 muss dabei natürlich ausreichend Kapazität aufweisen, um den hohen Druck P1 von beispielsweise 40 bis 70 bar für einen ausreichenden Zeitraum aufrechterhalten zu können, damit das flüssige Metall 9 ausreichend lange und ausreichend schnell aus der
Trennkammer R1 in die Trennkammer R2 fließt. In einer Ausgestaltung kann beispielsweise vorgesehen sein, dass der Druckspeicher R3 ein Volumen von etwa 31 bei einem maximalen Druck von 200 bar aufweist.In this operating state (step S3 in FIG. 3), the X-ray emitter according to the invention is produced operated, the electron beam is thus turned on and it is generated X-rays. The liquid metal 9 flows at the desired speed of, for example, 100 cm 3 / s for the duration of the data acquisition, for example 20 s at CT, from the separation chamber R1 into the separation chamber R2. The valves V1 and V2 are continuously open (or fully or partially closed) to apply the required working pressure. The pressure accumulator R3 must of course have sufficient capacity to maintain the high pressure P1, for example, 40 to 70 bar for a sufficient period of time, so that the liquid metal 9 sufficiently long and fast enough from the
Separation chamber R1 flows into the separation chamber R2. In one embodiment, for example, be provided that the pressure accumulator R3 has a volume of about 31 at a maximum pressure of 200 bar.

Wenn die Datenerfassung beendet ist, wird der Elektronenstrahl 4 abgeschaltet und die Ventile V1 und V2 werden gegenüber der Atmosphäre geöffnet, so dass der Druck P1 und P2 wieder auf Atmosphärendruck abfällt (Schritt S4). Das flüssige Metall 9 befindet sich nun größtenteils oder vollständig in der Trennkammer R2, wie in Figur 2c gezeigt ist. Da sich das flüssige Metall 9 aufgrund der auftreffenden Elektronen 4 in der Elektronenauftreffzone 8 erhitzt hat, sind Kühlkanäle 14 vorgesehen, mit denen das flüssige Metall 9 in der Trennkammer R2 gekühlt werden kann, vorzugsweise auf eine Temperatur von 60 bis 65 °C, so dass das flüssige Metall 9 in flüssigem Zustand bleibt.When the data acquisition is completed, the electron beam 4 is turned off and the valves V1 and V2 are opened to the atmosphere, so that the pressure P1 and P2 drops back to atmospheric pressure (step S4). The liquid metal 9 is now largely or completely in the separation chamber R2, as shown in Figure 2c. Since the liquid metal 9 has heated due to the incident electrons 4 in the electron impact zone 8, cooling channels 14 are provided, with which the liquid metal 9 can be cooled in the separation chamber R2, preferably to a temperature of 60 to 65 ° C, so that the liquid metal 9 remains in a liquid state.

In einem letzten Schritt (S5) wird schließlich auch mittels der Pumpe 13 dafür gesorgt, dass der Druck in dem Druckspeicher R3 wieder "nachgeladen" wird, so dass wieder ausreichend Druck für den nächsten Durchlauf zur Verfügung steht. Die Leistung der Pumpe 13 braucht also nicht auf die höchste erforderliche Leistung, die beim Betrieb des Röntgenstrahlers zur Verfügung gestellt werden muss, abgestellt werden, sondern muss nur so ausgelegt werden, dass der Druck in dem Druckspeicher R3 während der Betriebspause wieder auf einen ausreichend hohen Druck eingestellt werden kann. Im Gegensatz dazu muss die Pumpe bei dem bekannten Röntgenstrahler für die volle Betriebsleistung ausgelegt sein.Finally, in a final step (S5), it is also ensured by means of the pump 13 that the pressure in the pressure accumulator R3 is again "reloaded" so that sufficient pressure is again available for the next run. The power of the pump 13 does not need to be turned off to the highest required power that must be provided during operation of the X-ray source, but must only be designed so that the pressure in the pressure accumulator R3 during the downtime again to a sufficiently high Pressure can be adjusted. In contrast, the pump must be designed with the known X-ray source for full operating performance.

Wie in den Figuren 2a bis 2c leicht zu erkennen ist, ist die Verengung 8 hinter dem Fenster 5 zu den Trennkammern R1 und R2 hin verlaufend asymmetrisch ausgestaltet. Dadurch soll erreicht werden, dass der Druckverlust, den das von der Trennkammer R1 zur Trennkammer R2 fließende flüssige Metall 9 im Betrieb einen möglichst geringen Druckverlust erfährt und somit eine möglichst hohe Flussgeschwindigkeit in der Elektronenauftreffzone erreicht. Die gezeigte Anordnung ist somit nur so zu betreiben, dass das flüssige Metall 9 im Betrieb immer von der Trennkammer R1 in die Trennkammer R2 gepresst wird. Alternativ kann die Verengung 8 jedoch auch symmetrisch ausgelegt sein, und es können auch Kühlkanäle 14 um die Trennkammer R1 vorgesehen werden, so dass das flüssige Metall 9 in beide Richtungen im Betrieb gepresst werden kann.
Alternativ zu der gezeigten Ausgestaltung sind auch weitere Möglichkeiten zur Ausübung des Drucks auf das flüssige Metall denkbar. So ist es beispielsweise möglich, anstatt des Gases 11 eine Flüssigkeit zu verwenden, die einen sehr niedrigen Siedepunkt aufweist und die mit einer Heizeinrichtung zum Sieden gebracht wird (also verdampft wird) um einen hohen Druck zu erzielen. Die verdampfte Flüssigkeit kann dann in einem Dampfspeicher vorgehalten werden, um im Betrieb dann den geforderten Druck auf das flüssige Metall ausüben zu können. Bei dieser Ausgestaltung würde eine Pumpe völlig überflüssig. Stattdessen wären nur Heizeinrichtungen erforderlich. Eine mechanische Bewegung, wie sie beispielsweise in einer Pumpe erfolgt, könnte somit vollständig entfallen, was insbesondere bei Einsatz eines solchen Röntgenstrahlers in einer CT-Gantry vorteilhaft ist.As can easily be seen in FIGS. 2 a to 2 c, the constriction 8 behind the window 5 is designed asymmetrically to extend to the separation chambers R 1 and R 2. This is intended to ensure that the pressure loss which the liquid metal 9 flowing from the separation chamber R1 to the separation chamber R2 undergoes the lowest possible pressure loss during operation and thus achieves the highest possible flow velocity in the electron impact zone. The arrangement shown is thus only to operate so that the liquid metal 9 is always pressed during operation of the separation chamber R1 in the separation chamber R2. Alternatively, however, the constriction 8 may also be designed symmetrically, and cooling channels 14 may also be provided around the separation chamber R1, so that the liquid metal 9 can be pressed in operation in both directions.
As an alternative to the embodiment shown, other possibilities for exerting the pressure on the liquid metal are also conceivable. Thus, for example, it is possible to use, instead of the gas 11, a liquid which has a very low boiling point and which is boiled (ie, evaporated) with a heating device to achieve a high pressure. The vaporized liquid can then be kept in a steam reservoir in order to then be able to exert the required pressure on the liquid metal during operation. In this embodiment, a pump would be completely unnecessary. Instead, only heaters would be required. A mechanical movement, as is done for example in a pump, could thus be completely eliminated, which is particularly advantageous when using such an X-ray source in a CT gantry.

Claims (13)

  1. An arrangement for generating X-rays upon incidence of electrons (4), which arrangement includes a liquid metal zone (7) in which a liquid metal (9) is provided as an X-ray target in such a manner that it can flow past a zone of electron incidence (8), characterized in that a pressure zone (10) which is separate from the liquid metal zone (7) is provided with a pressure medium (11) in such a manner that the pressure medium (11) can exert a pressure on the liquid metal (9) present in the liquid metal zone (7) in order to force the liquid metal (9) past the zone of electron incidence (8), the pressure zone (10) being provided with a pressure accumulator (R3) which can be replenished in order to apply the pressure.
  2. An arrangement as claimed in claim 1, characterized in that the liquid metal zone (7) and the pressure zone (10) are separated from one another, by way of respective separating means (M1, M2), so as to adjoin one another in two separating zones (R1, R2), the separating means (M1, M2) being constructed so as to be movable in such a manner that pressure can be exerted on the liquid metal (9), via the separating means (M1, M2), in both separating zones (R1, R2).
  3. An arrangement as claimed in claim 2, characterized in that the separating zones are provided as two-piece separating chambers (R1, R2) with a respective liquid metal chamber (L1, L2) and a pressure medium chamber (G1, G2) which are separated from one another by a flexible diaphragm (M 1, M2).
  4. An arrangement as claimed in claim 2, characterized in that the separating zones (R1, R2) are constructed as cylinders with a displaceable piston.
  5. An arrangement as claimed in claim 1, characterized in that a gas, notably air, is used as the pressure medium (11), and that a gas pressure chamber is provided as the pressure accumulator (R3), a pump (13) being provided so as to replenish the pressure accumulator (R3).
  6. An arrangement as claimed in claim 1, characterized in that the pressure medium (11) used is a hydraulic liquid, notably a hydraulic oil, and that a hydraulic pressure chamber is provided as the pressure accumulator (R3).
  7. An arrangement as claimed in claim 1, characterized in that a liquid, notably water, is used as the pressure medium (11), and that a vapor chamber is provided as the pressure accumulator (R3), the liquid in the pressure accumulator being evaporated in order to replenish the pressure accumulator.
  8. An arrangement as claimed in claim 1, characterized in that there are provided control means (15; V1, V2) for controlling the application of a desired pressure to the liquid metal (9) in such a manner that the liquid metal (9) flows past the zone of electron incidence (8) at a desired flow speed.
  9. An arrangement as claimed in claim 8, characterized in that the control means include controllable valves (V1, V2) in the pressure zone (10) in order to control the pressure from the pressure accumulator (R3) which is exerted on the liquid metal (9) in the liquid metal zone (7).
  10. An arrangement as claimed in claim 1, characterized in that the liquid metal zone (7) is provided with a constriction (8) in the zone of electron incidence and that the constriction (8) is conceived so as to be asymmetrical at the two sides of the zone of electron incidence.
  11. An arrangement as claimed in claim 2, characterized in that at least one of the two separating zones (R1, R2) is provided with cooling means (14) for cooling the liquid metal (9) heated during operation.
  12. An X-ray source which includes an electron source (3) for the emission of electrons and an arrangement (2) for generating X-rays as claimed in claim 1.
  13. An X-ray device which includes an X-ray detector and an X-ray source as claimed in claim 12.
EP02100714A 2001-06-19 2002-06-17 X-ray source having a liquid metal target Expired - Lifetime EP1271602B8 (en)

Applications Claiming Priority (2)

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DE10129463 2001-06-19
DE10129463A DE10129463A1 (en) 2001-06-19 2001-06-19 X-ray tube with a liquid metal target

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US20030016789A1 (en) 2003-01-23
EP1271602B8 (en) 2007-05-30
JP2003066200A (en) 2003-03-05
US6647094B2 (en) 2003-11-11
EP1271602A1 (en) 2003-01-02
DE10129463A1 (en) 2003-01-02
JP4338943B2 (en) 2009-10-07
DE50208680D1 (en) 2006-12-28

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