EP0292055A2 - Radiation source for the generation of essentially monochromatic X-rays - Google Patents

Radiation source for the generation of essentially monochromatic X-rays Download PDF

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Publication number
EP0292055A2
EP0292055A2 EP88200941A EP88200941A EP0292055A2 EP 0292055 A2 EP0292055 A2 EP 0292055A2 EP 88200941 A EP88200941 A EP 88200941A EP 88200941 A EP88200941 A EP 88200941A EP 0292055 A2 EP0292055 A2 EP 0292055A2
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European Patent Office
Prior art keywords
radiation
anode
radiation source
source according
screen
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EP88200941A
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German (de)
French (fr)
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EP0292055A3 (en
EP0292055B1 (en
Inventor
Geoffrey Dr. Harding
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Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
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Philips Patentverwaltung GmbH
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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Priority to AT88200941T priority Critical patent/ATE74690T1/en
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00X-ray tubes
    • H01J35/02Details
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00X-ray tubes
    • H01J35/02Details
    • H01J35/04Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00X-ray tubes
    • H01J35/02Details
    • H01J35/04Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H01J35/06Cathodes
    • H01J35/066Details of electron optical components, e.g. cathode cups
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00X-ray tubes
    • H01J2235/16Vessels
    • H01J2235/165Shielding arrangements
    • H01J2235/168Shielding arrangements against charged particles
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00X-ray tubes
    • H01J35/02Details
    • H01J35/04Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H01J35/08Anodes; Anti cathodes
    • H01J35/112Non-rotating anodes
    • H01J35/116Transmissive anodes
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00X-ray tubes
    • H01J35/02Details
    • H01J35/16Vessels; Containers; Shields associated therewith
    • H01J35/18Windows
    • H01J35/186Windows used as targets or X-ray converters

Definitions

  • the invention relates to a radiation source for generating an essentially monochromatic X-ray radiation with a cathode for generating electrons accelerated to an anode and with a conical body enclosed by the anode, which converts X-radiation impinging on it into fluorescent radiation and which has a tapered end and converges to one Radiation leakage points.
  • Such a radiation source is known from DE-OS 22 59 382.
  • the monochromatic radiation is formed by the fluorescent radiation which emanates from the body when it is struck by primary X-ray radiation.
  • the primary X-ray radiation is suppressed by a collimator located at a suitable location.
  • the anode In the known radiation source, the anode is designed as a so-called transmission anode, ie it is struck by electrons on its outer surface and the X-ray radiation that strikes the conical body emerges from the inner surface.
  • the thickness of the anode has to be a compromise between the contradictory demands, on the one hand, to absorb as many electrons as possible and, on the other hand, to weaken the generated X-rays as little as possible. This results in relatively small thicknesses, which results in poor heat dissipation and thus a limited tube load capacity.
  • the object of the present invention is to design a radiation source of the type mentioned at the outset in such a way that there is an increased thermal load capacity.
  • This object is achieved in that the anode is hit on its inner surface facing the body by the electrons emitted from the cathode.
  • the heat can be dissipated much better from the anode, for example by liquid cooling and / or by using a relatively thick-walled anode.
  • a further development of the invention provides that the inner surface of the anode facing the body has the shape of a truncated cone jacket tapering towards the radiation exit.
  • the anode consists of a solid metal block, which is provided on its inner surface with a heavy-duty metal layer.
  • the material of the metal block of the anode can consist of a thermally highly conductive material, for example copper, while the metal on the inner surface can be selected with a view to the highest possible fluorescence radiation yield.
  • the material for the inner surface of the anode and the outer surface of the body is selected so that the characteristic X-ray radiation emitted from the anode has an energy that is slightly greater than the K-absorption edge of the body. Since X-rays, the energy of which is slightly above the absorption edge of a material, are converted into fluorescence radiation to a particularly high percentage, this results in an increased intensity of the fluorescence radiation.
  • a cylindrical metal screen which surrounds the body and which only weakens the X-ray radiation only slightly.
  • the screen absorbs the secondary electrons and prevents them from generating X-rays with an energy different from the energy of the fluorescent radiation.
  • the rotationally symmetrical radiation source has a cylindrical housing 1, to which a cathode arrangement 3 with an annular or spiral cathode 4 is attached via a ceramic insulator 2.
  • a cathode arrangement 3 with an annular or spiral cathode 4 is attached via a ceramic insulator 2.
  • an electron beam indicated by the dashed lines 4a, is emitted, which strikes the inner surface of an anode, which is shaped like the shell of a truncated cone. This results in a relatively even distribution of the electrons on the inner surface of the anode.
  • the anode consists of a metal block 5a made of thermally highly conductive material, preferably copper, which is coated on its inner surface with a heavy-duty metal layer, in which X-rays are generated by the electron bombardment.
  • the X-ray radiation strikes a target 7 through a thin cylindrical screen 6, which is conical on its side facing away from the cathode and converts the primary radiation striking it into essentially monochromatic fluorescent radiation.
  • the screen 6, which carries the target 7, has the task of keeping scattered electrons away from the target 7. These stray electrons would generate an undesirable bremsradiation spectrum when they hit the target 7.
  • the screen 6 absorbs too much primary X-ray radiation and on the other hand even emits X-radiation due to stray or secondary electrons, the screen 6 is as thin-walled as is just permitted for mechanical reasons and consists of a low-atom material, e.g. Titanium.
  • the primary X-ray radiation emanating from the anode 5a, 5b is suppressed by a collimator arrangement 8, in the center of which the screen 6 is attached in a vacuum-tight manner.
  • the collimator consists of a radiation-absorbing material or a plurality of plates of such a material which are offset with respect to one another in the direction of the axis of symmetry, the thickness of the collimator or the spacing of the outer plates of this collimator being chosen such that from the anode outgoing primary X-ray radiation must hit the collimator before it reaches the radiation exit 9.
  • the energy of the fluorescence radiation depends on the material of the target. If tantalum is chosen as the material, the energy of the fluorescent radiation is 57.5 keV (K ⁇ 1 line). If a fluorescence radiation with higher or lower energy is to be generated, the tantalum target must be replaced by a target which consists of an element or an alloy with a higher or lower atomic number.
  • the tube voltage (expressed in kV) must be about twice as high as the energy of the fluorescent radiation (expressed in keV).
  • it is expedient to release the target e.g. with a screw connection to connect to the shield.
  • the screen must be designed so that it hermetically seals the inside of the evacuated housing of the radiation source to the outside
  • the layer 5b in which the primary X-ray radiation is generated, has a high atomic number and is expediently chosen such that the energy of the characteristic radiation generated in this layer lies slightly above the K absorption edge of the target 7, because this results in a particularly good implementation in fluorescence radiation. If the target consists of tantalum (K absorption edge at 67.4 keV), this condition is met by a layer 5b of gold (K ⁇ line at 68.8 keV).
  • the layer 5b is preferably applied to a solid metal block 5a made of copper.
  • the back of this copper block is cooled by a cooling liquid which flows into a cavity 10, which is hermetically sealed from the inside of the tube, around the copper block from the outside in a manner not shown in detail.
  • a cooling liquid which flows into a cavity 10, which is hermetically sealed from the inside of the tube, around the copper block from the outside in a manner not shown in detail.
  • water is preferably used as the cooling liquid.
  • a metal block enclosed by a cavity for cooling it is also possible to use a metal block in which cooling channels, for example in the form of a spiral, have already been incorporated. With a suitable design, this allows the cooling surface and thus also the maximum electrical power that can be supplied to be increased.
  • the fluorescence radiation generated on the target 7 is not completely monochromatic. This is because other lines besides the desired K ⁇ lines are excited, e.g. the higher energy Kß line or L lines with much lower energy.
  • the Kß line can be suppressed by a radiation filter arranged in the radiation outlet, which consists of a material whose absorption edge lies between the K ⁇ and the Kß line.
  • filters made of ytterbium or thulium are suitable as radiation filters.
  • the soft lines can optionally be suppressed by the same filter or by a filter made of a material with a lower atomic number, which is dimensioned such that the desired K ⁇ line is only slightly weakened, while the L lines are largely suppressed.

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  • X-Ray Techniques (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)

Abstract

The invention relates to a fluorescence radiation source in which an anode which encloses a member is struck by electrons on its side which faces the member and in which the primary X-ray radiation generated in the anode generates fluorescence radiation in the member. The member is preferably arranged within an enclosing shield which keeps scattered electrons remote from the member.

Description

Die Erfindung betrifft eine Strahlenquelle zur Erzeugung einer im wesentlichen monochromatischen Röntgenstrahlung mit einer Kathode zur Erzeugung von auf eine Anode be­schleunigten Elektronen und mit einem von der Anode um­schlossenen kegelförmigen Körper, der auf ihn auftreffende Röntgenstrahlung in Fluoreszenzstrahlung umsetzt und der mit seinem sich verjüngenden Ende auf einen Strahlenaus­tritt weist.The invention relates to a radiation source for generating an essentially monochromatic X-ray radiation with a cathode for generating electrons accelerated to an anode and with a conical body enclosed by the anode, which converts X-radiation impinging on it into fluorescent radiation and which has a tapered end and converges to one Radiation leakage points.

Eine solche Strahlenquelle ist aus der DE-OS 22 59 382 bekannt. Die monochromatische Strahlung wird bei dieser Strahlenquelle durch die Fluoreszenzstrahlung gebildet, die von dem Körper ausgeht, wenn er durch primäre Röntgen­strahlung getroffen wird. Die primäre Röntgenstrahlung wird durch einen an geeigneter Stelle befindlichen Kollimator unterdrückt.Such a radiation source is known from DE-OS 22 59 382. In this radiation source, the monochromatic radiation is formed by the fluorescent radiation which emanates from the body when it is struck by primary X-ray radiation. The primary X-ray radiation is suppressed by a collimator located at a suitable location.

Bei der bekannten Strahlenquelle ist die Anode als soge­nannte Transmissionsanode ausgebildet, d.h. sie wird auf ihrer Außenfläche von Elektronen getroffen und die Röntgenstrahlung, die auf den kegelförmigen Körper auf­trifft, tritt aus der Innenfläche aus. Die Dicke der Anode muß ein Kompromiß sein zwischen den gegensätzlichen Forde­rungen, einerseits möglichst alle Elektronen zu absor­bieren und andererseits die erzeugte Röntgenstrahlung möglichst wenig zu schwächen. Dabei ergeben sich relativ geringe Dicken, woraus eine schlechte Wärmeabfuhr und damit eine begrenzte Röhrenbelastbarkeit resultieren.In the known radiation source, the anode is designed as a so-called transmission anode, ie it is struck by electrons on its outer surface and the X-ray radiation that strikes the conical body emerges from the inner surface. The thickness of the anode has to be a compromise between the contradictory demands, on the one hand, to absorb as many electrons as possible and, on the other hand, to weaken the generated X-rays as little as possible. This results in relatively small thicknesses, which results in poor heat dissipation and thus a limited tube load capacity.

Aufgabe der vorliegenden Erfindung ist es, eine Strahlen­quelle der eingangs genannten Art so auszugestalten, daß sich eine erhöhte thermische Belastbarkeit ergibt.The object of the present invention is to design a radiation source of the type mentioned at the outset in such a way that there is an increased thermal load capacity.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß die Anode auf ihrer dem Körper zugewandten Innenfläche von den aus der Kathode emittierten Elektronen getroffen wird.This object is achieved in that the anode is hit on its inner surface facing the body by the electrons emitted from the cathode.

Da bei dieser Bauform der Anode nur deren Innenfläche dem Elektronenbeschuß ausgesetzt und Ausgangspunkt der Röntgenstrahlung ist, kann die Wärme wesentlich besser aus der Anode abgeführt werden, beispielsweise durch eine Flüssigkeitskühlung und/oder dadurch, daß eine relativ dickwandige Anode verwendet wird.Since in this design the anode only its inner surface is exposed to the electron bombardment and the starting point of the X-rays, the heat can be dissipated much better from the anode, for example by liquid cooling and / or by using a relatively thick-walled anode.

Eine Weiterbildung der Erfindung sieht vor, daß die dem Körper zugewandte Innenfläche der Anode die Form eines sich zum Strahlenaustritt hin verjüngenden Kegelstumpf­mantels aufweist. Bei dieser Ausgestaltung, bei der das sich verjüngende Ende der Anode dem Strahlenaustritt und das sich erweiternde Ende der Kathode zugewandt ist, ergibt sich eine relativ gleichmäßige Verteilung der Elektronen über die Anodenfläche, so daß auch die ther­mische Belastbarkeit vergleichmäßigt wird.A further development of the invention provides that the inner surface of the anode facing the body has the shape of a truncated cone jacket tapering towards the radiation exit. With this configuration, in which the tapered end of the anode faces the radiation exit and the widening end of the cathode, the electrons are distributed relatively evenly over the anode surface, so that the thermal load capacity is also made more uniform.

Eine andere Weiterbildung sieht vor, daß die Anode aus einem massiven Metallblock besteht, der auf seiner Innen­fläche mit einer schweratomigen Metallschicht versehen ist. Das Material des Metallblocks der Anode kann dabei aus einem thermisch gut leitenden Werkstoff bestehen, beispielsweise Kupfer, während das Metall auf der Innen­fläche im Hinblick auf eine möglichst hohe Fluoreszenz­strahlungsausbeute gewählt werden kann.Another development provides that the anode consists of a solid metal block, which is provided on its inner surface with a heavy-duty metal layer. The material of the metal block of the anode can consist of a thermally highly conductive material, for example copper, while the metal on the inner surface can be selected with a view to the highest possible fluorescence radiation yield.

Eine andere Weiterbildung sieht vor, daß das Material für die Innenfläche der Anode und die Außenfläche des Körpers so gewählt ist, daß die aus der Anode emittierte charakte­ristische Röntgenstrahlung eine Energie besitzt, die geringfügig größer ist als die K-Absorptionskante des Körpers. Da Röntgenstrahlung, deren Energie geringfügig oberhalb der Absorptionskante eines Materials liegt, in diesem zu einem besonders hohen Prozentsatz in Fluores­zenzstrahlung umgesetzt wird, ergibt sich dadurch eine vergrößerte Intensität der Fluoreszenzstrahlung.Another development provides that the material for the inner surface of the anode and the outer surface of the body is selected so that the characteristic X-ray radiation emitted from the anode has an energy that is slightly greater than the K-absorption edge of the body. Since X-rays, the energy of which is slightly above the absorption edge of a material, are converted into fluorescence radiation to a particularly high percentage, this results in an increased intensity of the fluorescence radiation.

Nach einer anderen Weiterbildung ist vorgesehen, daß sich zwischen der Anode und dem Körper ein den Körper um­schließender zylinderförmiger Metallschirm befindet, der die Röntgenstrahlung nur geringfügig schwächt. Der Schirm absorbiert die Sekundärelektronen und verhindert, daß dadurch in dem Körper Röntgenstrahlung mit einer von der Energie der Fluoreszenzstrahlung abweichenden Energie erzeugt wird.According to another development, it is provided that between the anode and the body there is a cylindrical metal screen which surrounds the body and which only weakens the X-ray radiation only slightly. The screen absorbs the secondary electrons and prevents them from generating X-rays with an energy different from the energy of the fluorescent radiation.

Die Erfindung wird nachstehend anhand der Zeichnung näher erläutert, die einen Querschnitt durch einen Teil einer erfindungsgemäßen Strahlenquelle zeigt.The invention is explained in more detail below with reference to the drawing, which shows a cross section through part of a radiation source according to the invention.

Die rotationssymmetrisch ausgebildete Strahlenquelle besitzt ein zylinderförmiges Gehäuse 1, an dem über einen Keramikisolator 2 eine Kathodenanordnung 3 mit einer ring- oder spiralförmigen Kathode 4 befestigt ist. Im Betriebs­zustand wird aus der Kathode ein durch die gestrichelten Linien 4a angedeutetes Elektronenbündel emittiert, das auf die Innenfläche einer Anode trifft, die wie der Mantel eines Kegelstumpfes geformt ist. Dadurch ergibt sich eine relativ gleichmäßige Verteilung der Elektronen auf der Anodeninnenfläche.The rotationally symmetrical radiation source has a cylindrical housing 1, to which a cathode arrangement 3 with an annular or spiral cathode 4 is attached via a ceramic insulator 2. In the operating state, an electron beam, indicated by the dashed lines 4a, is emitted, which strikes the inner surface of an anode, which is shaped like the shell of a truncated cone. This results in a relatively even distribution of the electrons on the inner surface of the anode.

Die Anode besteht aus einem Metallblock 5a aus thermisch gut leitenden Material, vorzugsweise Kupfer, das auf seiner Innenfläche mit einer schweratomigen Metallschicht beschichtet ist, in der durch den Elektronenbeschuß Röntgenstrahlung entsteht.The anode consists of a metal block 5a made of thermally highly conductive material, preferably copper, which is coated on its inner surface with a heavy-duty metal layer, in which X-rays are generated by the electron bombardment.

Die Röntgenstrahlung trifft durch einen dünnen zylin­drischen Schirm 6 hindurch auf ein Target 7, das auf seiner von der Kathode abgewandten Seite kegelförmig gestaltet ist und die auf ihn auftreffende Primärstrahlung in im wesentlichen monochromatische Fluoreszenzstrahlung umsetzt.The X-ray radiation strikes a target 7 through a thin cylindrical screen 6, which is conical on its side facing away from the cathode and converts the primary radiation striking it into essentially monochromatic fluorescent radiation.

Der Schirm 6, der das Target 7 trägt, hat die Aufgabe, Streuelektronen vom Target 7 fernzuhalten. Diese Streu­elektronen würden beim Auftreffen auf das Target 7 ein unerwünschtes Bremsstrahlungsspektrum erzeugen. Um zu vermeiden, daß einerseits der Schirm 6 zuviel primäre Röntgenstrahlung absorbiert und andererseits durch auf­treffende Streu- oder Sekundärelektronen selbst Röntgen­strahlung emittiert, ist der Schirm 6 so dünnwandig wie aus mechanischen Gründen gerade noch zulässig und besteht aus einem niederatomigen Material, z.B. Titan.The screen 6, which carries the target 7, has the task of keeping scattered electrons away from the target 7. These stray electrons would generate an undesirable bremsradiation spectrum when they hit the target 7. In order to avoid that on the one hand the screen 6 absorbs too much primary X-ray radiation and on the other hand even emits X-radiation due to stray or secondary electrons, the screen 6 is as thin-walled as is just permitted for mechanical reasons and consists of a low-atom material, e.g. Titanium.

Das offene Ende des Schirms, dem die Spitze des kegel­förmigen Targets 7 zugewandt ist, bildet den Strahlenaus­tritt 9 für die erzeugte Fluoreszenzstrahlung. Die von der Anode 5a, 5b ausgehende primäre Röntgenstrahlung wird von einer Kollimatoranordnung 8 unterdrückt, in deren Zentrum der Schirm 6 vakuumdicht angebracht ist. Der Kollimator besteht aus einem strahlenabsorbierenden Material oder mehreren in Richtung der Symmetrieachse gegeneinander ver­setzten Platten aus einem solchen Material, wobei die Dicke des Kollimators bzw. der Abstand der äußeren Platten dieses Kollimators so gewählt sind, daß von der Anode aus­ gehende primäre Röntgenstrahlung auf den Kollimator treffen muß, bevor sie den Strahlenaustritt 9 erreicht.The open end of the screen, which the tip of the conical target 7 faces, forms the beam exit 9 for the generated fluorescent radiation. The primary X-ray radiation emanating from the anode 5a, 5b is suppressed by a collimator arrangement 8, in the center of which the screen 6 is attached in a vacuum-tight manner. The collimator consists of a radiation-absorbing material or a plurality of plates of such a material which are offset with respect to one another in the direction of the axis of symmetry, the thickness of the collimator or the spacing of the outer plates of this collimator being chosen such that from the anode outgoing primary X-ray radiation must hit the collimator before it reaches the radiation exit 9.

Die Energie der Fluoreszenzstrahlung hängt von dem Material des Targets ab. Wenn Tantal als Material gewählt wird, ergibt sich eine Energie der Fluoreszenzstrahlung von 57,5 keV (Kα₁-Linie). Wenn eine Fluoreszenzstrahlung mit höherer oder niedrigerer Energie erzeugt werden soll, muß das Tantaltarget durch eine Target ersetzt werden, das aus einem Element oder einer Legierung mit höherer bzw. niedrigerer Ordnungszahl besteht. Die Röhrenspannung (ausgedrückt in kV) muß dabei jeweils etwa doppelt so groß sein wie die Energie der Fluoreszenzstrahlung (ausgedrückt in keV). Um zwecks Erzeugung von monochromatischer Strahlung mit unterschiedlicher Wellenlänge aus unter­schiedlichem Material bestehende Targets verwenden zu können, ist es zweckmäßig, das Target lösbar, z.B. durch eine Schraubverbindung, mitdem Schirm zu verbinden. Der Schirm muß dabei so gestaltet sein, daß er das Innere des evakuierten Gehäuses der Strahlenquelle hermetisch nach außen hin abschließtThe energy of the fluorescence radiation depends on the material of the target. If tantalum is chosen as the material, the energy of the fluorescent radiation is 57.5 keV (Kα₁ line). If a fluorescence radiation with higher or lower energy is to be generated, the tantalum target must be replaced by a target which consists of an element or an alloy with a higher or lower atomic number. The tube voltage (expressed in kV) must be about twice as high as the energy of the fluorescent radiation (expressed in keV). In order to be able to use targets consisting of different materials for the purpose of generating monochromatic radiation with different wavelengths, it is expedient to release the target, e.g. with a screw connection to connect to the shield. The screen must be designed so that it hermetically seals the inside of the evacuated housing of the radiation source to the outside

Die Schicht 5b, in der die primäre Röntgenstrahlung erzeugt wird, hat eine hohe Ordnungszahl und ist zweck­mäßigerweise so gewählt, daß die Energie der in dieser Schicht erzeugten charakteristischen Strahlung geringfügig oberhalb der K-Absorptionskante des Targets 7 liegt, weil sich dabei eine besonders gute Umsetzung in Fluoreszenz­strahlung ergibt. Wenn das Target aus Tantal besteht (K-Absorptionskante bei 67,4 keV), wird diese Bedingung durch eine Schicht 5b aus Gold (Kα-Linie bei 68,8 keV) erfüllt.The layer 5b, in which the primary X-ray radiation is generated, has a high atomic number and is expediently chosen such that the energy of the characteristic radiation generated in this layer lies slightly above the K absorption edge of the target 7, because this results in a particularly good implementation in fluorescence radiation. If the target consists of tantalum (K absorption edge at 67.4 keV), this condition is met by a layer 5b of gold (Kα line at 68.8 keV).

Wie bereits erwähnt, ist die Schicht 5b auf einen massiven Metallblock 5a vorzugsweise aus Kupfer aufgebracht. Die Rückseite dieses Kupferblocks wird von einer Kühlflüssig­keit gekühlt, die in einen zum Röhreninnern hin hermetisch abgedichteten Hohlraum 10 um den Kupferblock herum in nicht näher dargestellter Weise von außen einströmt. Da die Anode 5a, 5b ebenso wie das Gehäuse 1 und der Kolli­mator 8 Massepotential führen, wird als Kühlflüssigkeit vorzugsweise Wasser eingesetzt. Anstelle eines von einem Hohlraum für die Kühlung umschlossenen Metallblocks kann auch ein Metallblock eingesetzt werden, in den bereits Kühlkanäle, beispielsweise in Spiralform, eingearbeitet sind. Dadurch läßt sich bei geeigneter Auslegung die Kühlfläche und damit auch die maximal zuführbare elek­trische Leistung vergrößern.As already mentioned, the layer 5b is preferably applied to a solid metal block 5a made of copper. The The back of this copper block is cooled by a cooling liquid which flows into a cavity 10, which is hermetically sealed from the inside of the tube, around the copper block from the outside in a manner not shown in detail. Since the anode 5a, 5b, like the housing 1 and the collimator 8, have ground potential, water is preferably used as the cooling liquid. Instead of a metal block enclosed by a cavity for cooling, it is also possible to use a metal block in which cooling channels, for example in the form of a spiral, have already been incorporated. With a suitable design, this allows the cooling surface and thus also the maximum electrical power that can be supplied to be increased.

Die auf dem Target 7 erzeugte Fluoreszenzstrahlung ist nicht völlig monochromatisch. Dies liegt daran, daß außer der erwünschten Kα-Linien auch andere Linien angeregt werden, z.B. die höherenergetische Kß-Linie oder L-Linien mit wesentlich niedrigerer Energie. Die Kß-Linie kann durch ein im Strahlenaustritt angeordnetes Strahlenfilter unterdrückt werden, das aus einem Material besteht, dessen Absorptionskante zwischen der Kα- und der Kß-Linie liegt. Bei einem Tantaltarget eignen sich als Strahlen­filter Filter aus Ytterbium oder Thulium. Die weichen Linien können gegebenenfalls durch das gleiche Filter oder durch ein Filter aus einem Material mit einer niedrigeren Ordnungszahl unterdrückt werden, das so bemessen ist, daß die erwünschte Kα-Linie nur unwesentlich geschwächt wird, während die L-Linien weitgehend unterdrückt sind.The fluorescence radiation generated on the target 7 is not completely monochromatic. This is because other lines besides the desired Kα lines are excited, e.g. the higher energy Kß line or L lines with much lower energy. The Kß line can be suppressed by a radiation filter arranged in the radiation outlet, which consists of a material whose absorption edge lies between the Kα and the Kß line. In the case of a tantalum target, filters made of ytterbium or thulium are suitable as radiation filters. The soft lines can optionally be suppressed by the same filter or by a filter made of a material with a lower atomic number, which is dimensioned such that the desired Kα line is only slightly weakened, while the L lines are largely suppressed.

Claims (12)

1. Strahlenquelle zur Erzeugung einer im wesentlichen monochromatischen Röntgenstrahlung mit einer Kathode (3, 4) zur Erzeugung von auf eine Anode (5a, 5b) beschleunigten Elektronen und mit einem von der Anode umschlossenen kegelförmigen Körper (7), der auf ihn auftreffende Röntgenstrahlung in Fluoreszenzstrahlung umsetzt und der mit seinem sich verjüngenden Ende auf einen Strahlenaustritt weist,
dadurch gekennzeichnet, daß die Anode auf ihrer dem Körper (7) zugewandten Innenfläche (5b) von den aus der Kathode (4) emittierten Elektronen getroffen wird.
1. Radiation source for generating an essentially monochromatic X-ray radiation with a cathode (3, 4) for generating electrons accelerated to an anode (5a, 5b) and with a conical body (7) enclosed by the anode, the X-radiation impinging on it in Converts fluorescence radiation and which points with its tapered end to a radiation exit,
characterized in that the anode on its inner surface (5b) facing the body (7) is struck by the electrons emitted from the cathode (4).
2. Strahlenquelle nach Anspruch 1,
dadurch gekennzeichnet, daß die Kathode (4) auf der vom Strahlenaustritt abgewandten Seite angeordnet ist und Ring- oder Spiralform aufweist.
2. radiation source according to claim 1,
characterized in that the cathode (4) is arranged on the side facing away from the radiation exit and has a ring or spiral shape.
3. Strahlenquelle nach einem der vorhergehenden Ansprüche,
dadurch gekennzeichnet, daß die dem Körper zugewandte Innenfläche (5b) der Anode die Form eines sich zum Strahlenaustritt hin verjüngenden Kegelstumpfmantels aufweist.
3. radiation source according to one of the preceding claims,
characterized in that the inner surface (5b) of the anode facing the body has the shape of a truncated cone tapering towards the radiation exit.
4. Strahlenquelle nach einem der Ansprüche 1 bis 3,
dadurch gekennzeichnet, daß die Anode auf ihrer Außen­fläche mit einer Kühlflüssigkeit kühlbar ist.
4. radiation source according to one of claims 1 to 3,
characterized in that the anode is coolable on its outer surface with a cooling liquid.
5. Strahlenquelle nach einem der vorhergehenden Ansprüche,
dadurch gekennzeichnet, daß die Kathode an negatives Hochspannungspotential und die Anode an Erdpotential angeschlossen sind und daß als Kühlmittel Wasser dient.
5. Radiation source according to one of the preceding claims,
characterized in that the cathode is connected to negative high voltage potential and the anode is connected to earth potential and that water is used as the coolant.
6. Strahlenquelle nach einem der vorhergehenden Ansprüche,
dadurch gekennzeichnet, daß die Anode aus einem massiven Metallblock (5a) besteht, der auf seiner Innenfläche mit einer schweratomigen Metallschicht (5b) versehen ist.
6. radiation source according to one of the preceding claims,
characterized in that the anode consists of a solid metal block (5a) which is provided on its inner surface with a heavy-atom metal layer (5b).
7. Strahlenquelle nach einem der vorhergehenden Ansprüche,
dadurch gekennzeichnet, daß das Material für die Innen­fläche der Anode und die Außenfläche des Körpers so gewählt ist, daß die aus der Anode emittierte charakte­ristische Röntgenstrahlung eine Energie besitzt, die geringfügig größer ist als die K-Absorptionskante der Außenfläche des Körpers.
7. Radiation source according to one of the preceding claims,
characterized in that the material for the inner surface of the anode and the outer surface of the body is selected so that the characteristic X-ray radiation emitted from the anode has an energy which is slightly greater than the K absorption edge of the outer surface of the body.
8. Strahlenquelle nach Anspruch 7,
dadurch gekennzeichnet, daß die Anode zumindest im Bereich der Innenfläche aus Gold besteht und daß der Körper aus Tantal besteht.
8. radiation source according to claim 7,
characterized in that the anode is made of gold at least in the area of the inner surface and that the body is made of tantalum.
9. Strahlenquelle nach einem der Ansprüch 1 bis 8,
dadurch gekennzeichnet, daß sich zwischen der Anode und dem Körper ein den Körper umschließender zylinderförmiger Metallschirm (6) befindet, der die Röntgenstrahlung nur geringfügig schwächt.
9. radiation source according to one of claims 1 to 8,
characterized in that between the anode and the body there is a cylindrical metal screen (6) which encloses the body and which weakens the X-ray radiation only slightly.
10. Strahlenquelle nach Anspruch 9,
dadurch gekennzeichnet, daß der Schirm (6) den Körper (7) trägt und das Gehäuse der Strahlenquelle vakuumdicht abschließt.
10. radiation source according to claim 9,
characterized in that the screen (6) supports the body (7) and seals the housing of the radiation source in a vacuum-tight manner.
11. Strahlenquelle nach Anspruch 9,
dadurch gekennzeichnet, daß der Schirm (6) nach außen offen ist und daß der Körper (7) lösbar mit dem Schirm verbunden ist.
11. Radiation source according to claim 9,
characterized in that the screen (6) is open to the outside and that the body (7) is detachably connected to the screen.
12. Strahlenquelle nach einem der vorhergehenden Ansprüche,
dadurch gekennzeichnet, daß im Strahlenaustritt ein Filter (9) aus einem Material angeordnet ist, dessen Absorptionskante zwischen der Kα- und der Kß-Linie des Körpers liegt.
12. Radiation source according to one of the preceding claims,
characterized in that a filter (9) made of a material is arranged in the radiation outlet, the absorption edge of which lies between the Kα and Kß lines of the body.
EP88200941A 1987-05-18 1988-05-11 Radiation source for the generation of essentially monochromatic x-rays Expired - Lifetime EP0292055B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT88200941T ATE74690T1 (en) 1987-05-18 1988-05-11 RADIATION SOURCE FOR PRODUCING SUBSTANTIALLY MONOCHROMATIC X-RAY RADIATION.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19873716618 DE3716618A1 (en) 1987-05-18 1987-05-18 RADIATION SOURCE FOR GENERATING AN ESSENTIAL MONOCHROMATIC X-RAY RADIATION
DE3716618 1987-05-18

Publications (3)

Publication Number Publication Date
EP0292055A2 true EP0292055A2 (en) 1988-11-23
EP0292055A3 EP0292055A3 (en) 1989-04-19
EP0292055B1 EP0292055B1 (en) 1992-04-08

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US (1) US4903287A (en)
EP (1) EP0292055B1 (en)
JP (1) JP2747295B2 (en)
AT (1) ATE74690T1 (en)
DE (2) DE3716618A1 (en)

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EP0432568A2 (en) * 1989-12-11 1991-06-19 General Electric Company X ray tube anode and tube having same
EP0459567A2 (en) * 1990-05-26 1991-12-04 Philips Patentverwaltung GmbH Source for quasi-monochromatic X-ray beam
EP0777255A1 (en) * 1995-11-28 1997-06-04 Philips Patentverwaltung GmbH X-ray tube, in particular microfocus X-ray tube
EP1418610A1 (en) * 2002-11-06 2004-05-12 feinfocus Röntgen-Systeme GmbH Microfocus X-ray tube
EP1988564A1 (en) * 2006-02-01 2008-11-05 Toshiba Electron Tubes & Devices Co., Ltd. X-ray source, and fluorescent x-ray analyzing device

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DE4215343A1 (en) * 1992-05-09 1993-11-11 Philips Patentverwaltung Filter method for an X-ray system and arrangement for carrying out such a filter method
US5433771A (en) * 1994-04-25 1995-07-18 Westinghouse Electric Corporation Hot gas filtration system fail-safe and thermal regeneration device
DE19509006C2 (en) * 1995-03-13 1998-11-05 Siemens Ag X-ray tube
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JP2007207539A (en) * 2006-02-01 2007-08-16 Toshiba Corp X-ray source and fluorescent x-ray analysis system
US8331534B2 (en) 2009-04-16 2012-12-11 Silver Eric H Monochromatic X-ray methods and apparatus
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US9368316B2 (en) * 2013-09-03 2016-06-14 Electronics And Telecommunications Research Institute X-ray tube having anode electrode
US10532223B2 (en) 2017-05-19 2020-01-14 Imagine Scientific, Inc. Monochromatic X-ray imaging systems and methods
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Cited By (9)

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EP0432568A2 (en) * 1989-12-11 1991-06-19 General Electric Company X ray tube anode and tube having same
EP0432568A3 (en) * 1989-12-11 1991-08-28 General Electric Company X ray tube anode and tube having same
EP0459567A2 (en) * 1990-05-26 1991-12-04 Philips Patentverwaltung GmbH Source for quasi-monochromatic X-ray beam
EP0459567A3 (en) * 1990-05-26 1992-01-02 Philips Patentverwaltung Gmbh Source for quasi-monochromatic x-ray beam
EP0777255A1 (en) * 1995-11-28 1997-06-04 Philips Patentverwaltung GmbH X-ray tube, in particular microfocus X-ray tube
EP1418610A1 (en) * 2002-11-06 2004-05-12 feinfocus Röntgen-Systeme GmbH Microfocus X-ray tube
US7050543B2 (en) 2002-11-06 2006-05-23 Feinfocus Röntgen-Systeme GmbH Microfocus X-ray tube
EP1988564A1 (en) * 2006-02-01 2008-11-05 Toshiba Electron Tubes & Devices Co., Ltd. X-ray source, and fluorescent x-ray analyzing device
EP1988564A4 (en) * 2006-02-01 2011-04-20 Toshiba Electron Tubes & Devic X-ray source, and fluorescent x-ray analyzing device

Also Published As

Publication number Publication date
JPS63304557A (en) 1988-12-12
JP2747295B2 (en) 1998-05-06
DE3869829D1 (en) 1992-05-14
DE3716618A1 (en) 1988-12-08
EP0292055A3 (en) 1989-04-19
ATE74690T1 (en) 1992-04-15
EP0292055B1 (en) 1992-04-08
US4903287A (en) 1990-02-20

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