EP0215034B1 - X-ray tube with a cylindrical metal component enclosing the anode and cathode - Google Patents

X-ray tube with a cylindrical metal component enclosing the anode and cathode Download PDF

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Publication number
EP0215034B1
EP0215034B1 EP86901329A EP86901329A EP0215034B1 EP 0215034 B1 EP0215034 B1 EP 0215034B1 EP 86901329 A EP86901329 A EP 86901329A EP 86901329 A EP86901329 A EP 86901329A EP 0215034 B1 EP0215034 B1 EP 0215034B1
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EP
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Prior art keywords
ceramic insulator
ray tube
ceramic
cathode
anode
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EP86901329A
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German (de)
French (fr)
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EP0215034A1 (en
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Engelbert Berger
Dieter-W. Zickert
Peter Gutknecht
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GESELLSCHAFT fur ELEKTRONISCHE ROHREN COMET BERN
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GESELLSCHAFT fur ELEKTRONISCHE ROHREN COMET BERN
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Priority to AT86901329T priority Critical patent/ATE40767T1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/16—Vessels; Containers; Shields associated therewith

Definitions

  • the present invention relates to an X-ray tube with a cylindrical metal part surrounding the anode and the cathode, from which at least one of the electrodes anode and cathode is electrically insulated by means of a disk-shaped ceramic insulator which is arranged at an axial end of the metal part.
  • Such an X-ray tube is known from DE-A-2855905.
  • Known x-ray tubes of this type have shields in the interior of the cylindrical metal part, which are shaped and arranged in such a way that the electrical field resulting on the inner surfaces of the ceramic insulators points in its direction away from the insulator surface against the interior of the x-ray tube. This largely prevents the inside surfaces of the ceramic insulators from being inevitable from field emission electrons from becoming electrically charged as a result of secondary electron emission, thereby reducing the dielectric strength of the X-ray tube.
  • the object of the present invention is to provide an X-ray tube of the type mentioned in the introduction, in which the shields mentioned are dispensable and yet the electrical field on the inner surface of the or each ceramic insulator points in its direction away from the insulator surface against the interior of the tube.
  • the disk-shaped ceramic insulator has a step-like or ramp-like design in radial directions on its axial end surface facing away from the interior of the X-ray tube, in order to form an annular axial recess which is filled with an insulating material whose dielectric constant is smaller than that of the Ceramic material, and that in the case of a ceramic insulator isolating the anode from the metal part, the recess is arranged radially inside and in the case of a ceramic insulator isolating the cathode from the metal part, the recess is arranged radially outside.
  • This configuration of the X-ray tube ensures, in a surprisingly simple manner, that the direction of the electrical field on the inner insulator surface points away from the insulator surface into the interior of the tube.
  • the electrical field strength is reduced at the locations where the field emission primarily occurs, namely at the so-called trip points.
  • the tripie point is the solder connection between the ceramic insulator and the high-voltage lead in the center of the insulator.
  • the triple point lies in the soldering connection between the outer circumference of the ceramic insulator and the cylindrical metal part.
  • the insulating material filling the recess of the ceramic insulator can be a part of a rubber-elastic disc which is pressed in the axial direction onto the step-shaped or ramp-shaped end surface of the ceramic insulator.
  • the x-ray tube shown has a cylindrical metal part 11 which is provided with a window 12 inserted in a vacuum-tight manner for the exit of the x-ray radiation.
  • a window 12 inserted in a vacuum-tight manner for the exit of the x-ray radiation.
  • annular disk-shaped ceramic insulator 13 At the upper axial end of the metal part 11 in FIG. 1 there is an annular disk-shaped ceramic insulator 13, the outer periphery of which is connected to the metal part 11 in a vacuum-tight manner.
  • the axial end face 16 of the ceramic insulator 13 facing away from the interior of the metal part 11 is offset radially outwards by a step 17 running in the circumferential direction, so that an annular axial depression 18 is formed on the ceramic insulator 13 adjacent to its outer circumference.
  • This depression 18 is filled by a portion 19 of a rubber-elastic washer 20, which is pressed onto the ceramic insulator 13 by means of its connecting part 21 in a manner known per se, which is not shown.
  • the rubber-elastic washer 20 has a smaller dielectric constant than the ceramic insulator 13. Expediently, there is a layer of insulation grease (not shown in FIG. 1) in the joints between the ceramic insulator 13 and the rubber-elastic washer 20 as well as between the connecting part 21 and the rubber-elastic washer 20.
  • annular disk-shaped ceramic insulator 23 At the lower axial end of the cylindrical metal part 11 in FIG. 1 there is also an annular disk-shaped ceramic insulator 23, the outer periphery of which is connected to the metal part 11 in a vacuum-tight manner.
  • the facing away from the interior of the metal part 11 The axial end face 26 of the ceramic insulator 23 is offset radially inward by a step 27 running in the circumferential direction, so that an annular axial recess 28 is formed on the ceramic insulator 23 adjacent to its inner circumference.
  • This recess 28 is completely filled by a portion 29 of a rubber-elastic washer 30.
  • the rubber-elastic washer 30 is pressed onto the ceramic insulator 23 in a manner not known per se.
  • the rubber-elastic washer 30 has a smaller dielectric constant than the ceramic insulator 23.
  • one layer (not shown) of insulation grease In the joints between the ceramic insulator 23 and the rubber-elastic washer 30 as well as between the connecting part 31 and the rubber-elastic washer 30 there is expediently one layer (not shown) of insulation grease.
  • the metal part 11 is connected to earth potential, while a voltage which is negative with respect to the earth potential is applied to the cathode 15 through the connection part 21 and a voltage which is positive with respect to the earth potential is applied through the connection part 31 to the anode 25.
  • potential lines are then set, such as, for. B. are indicated by the dashed lines 32 and 33 in Fig. 1.
  • the potential lines 32 in the region of the ceramic insulator 13 assume a diverging profile that deviates from the axis-parallel direction, in such a way that on the flat inner end surface 34 of the Ceramic insulator 13 which have electrical field vectors 35, which are always at right angles to the potential lines 32, away from the ceramic insulator 13 against the interior of the X-ray tube.
  • the recess 28 of the other ceramic insulator 23 which is filled with insulating material 29 with a lower dielectric constant, has the result that the potential lines 33 in the area of the ceramic insulator 23 assume a converging course and therefore the electric field vectors 36 on the flat inner end surface 37 of the ceramic insulator 23 have directions pointing away from this towards the inside of the X-ray tube.
  • the angle between the field vectors 35 and 36 on the one hand and the inner end surface 34 and 37 of the ceramic insulator 13 and 23 on the other hand is due to the difference in the dielectric constants of the ceramic material and the rubber-elastic insulating material due to the radial width and the axial depth of the recess 18 or 28 and determined by the dimensions of the ceramic insulator 13 or 23. Because both on the cathode side and on the anode side the electrical field strength points in their direction away from the inner end face of the ceramic insulator 13 and 23 into the interior of the X-ray tube, charges on the ceramic insulators 13 and 23 as well as the associated field strength increases are effectively avoided. In comparison to similar known X-ray tubes, in which the ceramic insulators each have flat outer end faces without the steps 17 and 27, the X-ray tube according to FIG. 1 has a noticeably higher joint dielectric strength.
  • the described advantages were checked and confirmed using a test X-ray tube.
  • the experimental X-ray tube with the structure shown in FIG. 1 had ceramic insulators 13 and 23 with an outside diameter of 107 mm and an inside diameter of 45 mm.
  • the axial thickness dimension of the ceramic insulators was 10 mm and was reduced to 7 mm at the location of the recess 18 or 28, so that the step 17 or 27 had a height of 3 mm.
  • the rubber-elastic washers 20 and 30 were made of silicone rubber with a dielectric constant of 3.2 and a Shore hardness of 28.
  • each rubber-elastic washer 20 and 30 were flat and parallel, and the outside diameter was 100 mm, the inside diameter 45 mm and the axial thickness 10 mm.
  • the X-ray tube could easily be operated with a voltage of up to 340 kV between the anode and cathode.
  • the ceramic insulator 113 shown in FIG. 2 for the cathode side of the X-ray tube has, on its axial end face 116 to be turned outwards, two steps 117 running in the circumferential direction, by means of which an axial recess 118 adjacent to the outer circumference of the ceramic insulator is formed.
  • the example of a ceramic insulator 213 for the cathode side of the X-ray tube shown in FIG. 3 has a ramp-shaped step 217 on its axial end face 216 to be turned outwards, by means of which an axial recess 218 adjacent to the outer circumference of the ceramic insulator is formed.
  • the ceramic insulator 123 shown in FIG. 4 for the anode side of the X-ray tube has two steps 117 running in the circumferential direction on its axial end face 126 to be turned outwards, by means of which an axial recess 128 adjacent to the inner circumference of the ceramic insulator is formed.
  • the ceramic insulator 223 for the anode side of the X-ray tube can also have a ramp-shaped step 227 on the axial end face to be turned outwards, so that an axial recess 228 adjacent to the inner circumference of the ceramic insulator is formed.
  • the depressions 118, 218, 128 and 228 of the ceramic insulators 113, 213, 123 and 223 according to FIGS. 2 to 5 are each made with rubber-elastic insulating material and its dielectric during assembly or installation of the X-ray tube constant is smaller than that of the ceramic material, completely filled.
  • X-ray tubes in which the cathode or the anode is electrically conductively connected to the cylindrical metal part.
  • the cathode or the anode is electrically conductively connected to the cylindrical metal part.
  • only the other anode or cathode is insulated from the cylindrical metal part by a ceramic insulator.
  • the invention is also applicable to such X-ray tubes in that the then only existing ceramic insulator in the manner described above is provided on its axial end surface facing away from the inside of the X-ray tube with a depression which is completely filled with an insulating material whose dielectric constant is smaller than that of the ceramic material is.

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  • X-Ray Techniques (AREA)
  • Microwave Tubes (AREA)

Abstract

In order to increase the dielectrical resistance without resorting to internal shielding, the ring plate shaped ceramic insulators (13, 23) which carry the cathode (15) and the anode (25) at the axial inside end surfaces (16, 26) of the X-ray tube are stepped down in radial directions by a step (17, 27) in order to permit the forming of an axial hollow (18, 28) running in the form of a ring. On the ceramic insulator (13) which carries the cathode (15), the hollow (18) borders on the external periphery of the ceramic insulator. Conversely, the hollow (28) on the ceramic insulator (23) carrying the anode (25) borders on the inside periphery of the ceramic insulator. Each of the hollows is entirely filled with an insulation material (19, 29), the dielectric constant of which is less than that of the ceramic material. This insulation material (19, 29) is functionally part of a rubber-elastic ring plate (20, 30) which is pressed onto the outer axial end surface of the respective ceramic insulator (13, 23).

Description

Die vorliegende Erfindung betrifft eine Röntgenröhre mit einem die Anode und die Kathode umgebenden zylindrischen Metallteil, von welchem zumindest eine der Elektroden Anode und Kathode mittels eines scheibenförmigen Keramikisolators elektrisch isoliert ist, der an einem achsialen Ende des Metallteils angeordnet ist.The present invention relates to an X-ray tube with a cylindrical metal part surrounding the anode and the cathode, from which at least one of the electrodes anode and cathode is electrically insulated by means of a disk-shaped ceramic insulator which is arranged at an axial end of the metal part.

Eine derartige Röntgenröhre ist aus DE-A-2855905 bekannt.Such an X-ray tube is known from DE-A-2855905.

Bekannte Röntgenröhren dieser Art weisen im Innenraum des zylindrischen Metallteils Abschirmungen auf, die derart geformt und angeordnet sind, dass das sich auf den innenliegenden Flächen der Keramikisolatoren ergebende elektrische Feld seiner Richtung nach von der Isolatorfläche weg gegen den Innenraum der Röntgenröhre weist. Hierdurch lässt sich weitgehend verhüten, dass die von unvermeidbaren Feldemissions-Elektronen getroffenen Innenflächen der Keramikisolatoren sich infolge von Sekundärelektronen-Emission elektrisch aufladen und dadurch die Spannungsfestigkeit der Röntgenröhre herabgesetzt wird.Known x-ray tubes of this type have shields in the interior of the cylindrical metal part, which are shaped and arranged in such a way that the electrical field resulting on the inner surfaces of the ceramic insulators points in its direction away from the insulator surface against the interior of the x-ray tube. This largely prevents the inside surfaces of the ceramic insulators from being inevitable from field emission electrons from becoming electrically charged as a result of secondary electron emission, thereby reducing the dielectric strength of the X-ray tube.

Aus der DE-U-6946926 ist ein konischer Keramikisolator mit einer im wesentlichen konstanten Wandstärke und mit einem aufvulkanisierten Gummiüberzug bekannt.From DE-U-6946926 a conical ceramic insulator with an essentially constant wall thickness and with a vulcanized rubber coating is known.

Aufgabe der vorliegenden Erfindung ist es, eine Röntgenröhre der eingangs genannten Art zu schaffen, bei welcher die erwähnten Abschirmungen entbehrlich sind und dennoch an der Innenfläche des oder jedes Keramikisolators das elektrische Feld seiner Richtung nach von der Isolatorfläche weg gegen das Röhreninnere weist.The object of the present invention is to provide an X-ray tube of the type mentioned in the introduction, in which the shields mentioned are dispensable and yet the electrical field on the inner surface of the or each ceramic insulator points in its direction away from the insulator surface against the interior of the tube.

Diese Aufgabe ist erfindungsgemäss dadurch gelöst, dass der scheibenförmige Keramikisolator an seiner vom Innenraum der Röntgenröhre abgewandten achsialen Endfläche in radialen Richtungen stufen- oder rampenförmig ausgebildet ist zur Bildung einer ringförmig verlaufenden achsialen Vertiefung, die mit einem Isoliermaterial ausgefüllt ist, dessen Dielektrizitätskonstante kleiner als diejenige des Keramikmaterials ist, und dass im Falle eines die Anode vom Metallteil isolierenden Keramikisolators die Vertiefung radial innen und im Falle eines die Kathode vom Metallteil isolierenden Keramikisolators die Vertiefung radial aussen angeordnet ist.According to the invention, this object is achieved in that the disk-shaped ceramic insulator has a step-like or ramp-like design in radial directions on its axial end surface facing away from the interior of the X-ray tube, in order to form an annular axial recess which is filled with an insulating material whose dielectric constant is smaller than that of the Ceramic material, and that in the case of a ceramic insulator isolating the anode from the metal part, the recess is arranged radially inside and in the case of a ceramic insulator isolating the cathode from the metal part, the recess is arranged radially outside.

Durch diese Ausbildung der Röntgenröhre wird auf überraschend einfache Weise erreicht, dass an der innenliegenden Isolatorfläche das elektrische Feld seiner Richtung nach von der Isolatorfläche weg in das Röhreninnere weist. Zusätzlich ergibt sich die vorteilhafte Wirkung, dass die elektrische Feldstärke an den Orten, an denen die Feldemission vornehmlich einsetzt, nämlich an den sogenannten TripIe-Punkten,reduziert ist. Auf der Kathodenseite befindetsichderTripie-Punktinderlöttechnischen Verbindung zwischen dem Keramikisolator und der Hochspannungszuführung im Zentrum des Isolators. Auf der Anodenseite hingegen IiegtderTriple-Punkt in der löttechnischen Verbindung zwischen dem Aussenumfang des Keramikisolators und dem zylindrischen Metallteil. Die beiden durch dieerfin- dungsgemässe Ausbitdung erzielten Effekte tragen zu einer merklichen Erhöhung der Spannungsfestigkeitder Röntgenröhre bei.This configuration of the X-ray tube ensures, in a surprisingly simple manner, that the direction of the electrical field on the inner insulator surface points away from the insulator surface into the interior of the tube. In addition, there is the advantageous effect that the electrical field strength is reduced at the locations where the field emission primarily occurs, namely at the so-called trip points. On the cathode side, the tripie point is the solder connection between the ceramic insulator and the high-voltage lead in the center of the insulator. On the anode side, however, the triple point lies in the soldering connection between the outer circumference of the ceramic insulator and the cylindrical metal part. The two effects achieved by the embossing according to the invention contribute to a noticeable increase in the dielectric strength of the X-ray tube.

In zweckmässiger Ausgestaltung der erfindungsgemässen Röntgenröhre kann das die Vertiefung des Keramikisolators ausfüllende Isoliermaterial eine Partie einer gummielastischen Scheibe sein, die in achsialer Richtung an die stufen- oder rampenförmig ausgebildete Endfläche des Keramikisolators angepresst ist.In an expedient embodiment of the X-ray tube according to the invention, the insulating material filling the recess of the ceramic insulator can be a part of a rubber-elastic disc which is pressed in the axial direction onto the step-shaped or ramp-shaped end surface of the ceramic insulator.

Weitere Einzelheiten und Vorteile ergeben sich aus der nun folgenden Beschreibung von Ausführungsbeispielen der Röntgenröhre gemäss der Erfindung sowie aus der zugehörigen Zeichnung, anhand welcher die Erfindung rein beispielsweise erläutert wird.

  • Fig. 1 zeigt einen achsialen Längsschnitt durch eine nach der Erfindung ausgebildete Röntgenröhre mit zugehörigen Anschlussteilen;
  • Fig. 2 und 3 zeigen je einen achsialen Schnitt durch zwei andere Ausführungsbeispiele des kathodenseitigen Keramikisolators;
  • Fig. 4 und 5 sind analoge Schnittdarstellungen von zwei weiteren Ausführungsbeispielen des anodenseitigen Keramikisolators.
Further details and advantages emerge from the following description of exemplary embodiments of the X-ray tube according to the invention and from the associated drawing, on the basis of which the invention is explained purely by way of example.
  • Fig. 1 shows an axial longitudinal section through an X-ray tube designed according to the invention with associated connecting parts;
  • 2 and 3 each show an axial section through two other exemplary embodiments of the cathode-side ceramic insulator;
  • 4 and 5 are analog sectional views of two further exemplary embodiments of the anode-side ceramic insulator.

Gemäss Fig. 1 weist die dargestellte Röntgenröhre einen zylindrischen Metallteil 11 auf, der mit einem vakuumdicht eingesetzten Fenster 12 für den Austritt der Röntgenstrahlung versehen ist. An dem in Fig. 1 oberen achsialen Ende des Metallteils 11 befindet sich ein ringscheibenförmiger Keramikisolator 13, dessen äusserer Umfang mit dem Metallteil 11 vakuumdicht verbunden ist. In der zentralen Durchbrechung des Keramikisolators 13 sitzt ebenfalls vakuumdicht eine Hochspannungsdurchführung 14, welche die Kathode 15 der Röntgenröhre trägt. Die vom Innenraum des Metallteils 11 abgewandte achsiale Endfläche 16 des Keramikisolators 13 ist durch eine in Umfangsrichtung verlaufende Stufe 17 radial auswärts abgesetzt, so dass am Keramikisolator 13 angrenzend an seinen äusseren Umfang eine ringförmige achsiale Vertiefung 18 gebildet ist. Diese Vertiefung 18 ist durch eine Partie 19 einer gummielastischen Ringscheibe 20 ausgefüllt, die mit- telseinesAnschlussteiles21 aufnichtdargestellte, an sich bekannte Weise an den Keramikisolator 13 angepresst ist. Die gummielastische Ringscheibe 20 weist eine kleinere Dielektrizitätskonstante als der Keramikisolator 13 auf. Zweckmässig befinden sich in den Fugen zwischen dem Keramikisolator 13 und der gummielastischen Ringscheibe 20 wie auch zwischen dem Anschlussteil 21 und der gummielastischen Ringscheibe 20 je eine (in Fig. 1 nicht dargestellte) Schicht Isolationsfett.1, the x-ray tube shown has a cylindrical metal part 11 which is provided with a window 12 inserted in a vacuum-tight manner for the exit of the x-ray radiation. At the upper axial end of the metal part 11 in FIG. 1 there is an annular disk-shaped ceramic insulator 13, the outer periphery of which is connected to the metal part 11 in a vacuum-tight manner. A high-voltage bushing 14, which carries the cathode 15 of the X-ray tube, also sits in a vacuum-tight manner in the central opening of the ceramic insulator 13. The axial end face 16 of the ceramic insulator 13 facing away from the interior of the metal part 11 is offset radially outwards by a step 17 running in the circumferential direction, so that an annular axial depression 18 is formed on the ceramic insulator 13 adjacent to its outer circumference. This depression 18 is filled by a portion 19 of a rubber-elastic washer 20, which is pressed onto the ceramic insulator 13 by means of its connecting part 21 in a manner known per se, which is not shown. The rubber-elastic washer 20 has a smaller dielectric constant than the ceramic insulator 13. Expediently, there is a layer of insulation grease (not shown in FIG. 1) in the joints between the ceramic insulator 13 and the rubber-elastic washer 20 as well as between the connecting part 21 and the rubber-elastic washer 20.

An dem in Fig. 1 unteren achsialen Ende des zylindrischen Metallteils 11 befindetsich ebenfalls ein ringscheibenförmiger Keramikisolator 23, dessen äusserer Umfang mit dem Metallteil 11 vakuumdicht verbunden ist. In der zentralen Durchbrechung des Keramikisolators 23 sitzt ebenfalls vakuumdicht eine Hochspannungsdurchführung 24, welche die Anode 25 der Röntgenröhre trägt. Die vom Innenraum des Metallteils 11 abgewandte achsiale Endfläche 26 des Keramikisolators 23 ist durch eine in Umfangsrichtung verlaufende Stufe 27 radial einwärts abgesetzt, so dass am Keramikisolator 23 angrenzend an seinen inneren Umfang eine ringförmige achsiale Vertiefung 28 gebildet ist. Diese Vertiefung 28 ist durch eine Partie 29 einer gummielastischen Ringscheibe 30 vollständig ausgefüllt. Mittels eines Anschlussteiles 31 ist die gummielastische Ringscheibe 30 auf nicht dargestellte, an sich bekannte Weise an den Keramikisolator 23 angepresst. Die gummielastische Ringscheibe 30 weist eine kleinere Dielektrizitätskonstante als der Keramikisolator 23 auf. In den Fugen zwischen dem Keramikisolator 23 und der gummielastischen Ringscheibe 30 wie auch zwischen dem Anschlussteil 31 und der gummielastischen Ringscheibe 30 befindet sich zweckmässig je eine (nicht dargestellte) Schicht Isolationsfett.At the lower axial end of the cylindrical metal part 11 in FIG. 1 there is also an annular disk-shaped ceramic insulator 23, the outer periphery of which is connected to the metal part 11 in a vacuum-tight manner. A high-voltage bushing 24, which carries the anode 25 of the X-ray tube, also sits in a vacuum-tight manner in the central opening of the ceramic insulator 23. The facing away from the interior of the metal part 11 The axial end face 26 of the ceramic insulator 23 is offset radially inward by a step 27 running in the circumferential direction, so that an annular axial recess 28 is formed on the ceramic insulator 23 adjacent to its inner circumference. This recess 28 is completely filled by a portion 29 of a rubber-elastic washer 30. By means of a connecting part 31, the rubber-elastic washer 30 is pressed onto the ceramic insulator 23 in a manner not known per se. The rubber-elastic washer 30 has a smaller dielectric constant than the ceramic insulator 23. In the joints between the ceramic insulator 23 and the rubber-elastic washer 30 as well as between the connecting part 31 and the rubber-elastic washer 30 there is expediently one layer (not shown) of insulation grease.

Zum Betrieb der beschriebenen Röntgenröhre wird der Metallteil 11 auf Erdpotential gelegt, während an die Kathode 15 eine gegenüber dem Erdpotential negative Spannung durch den Anschlussteil 21 hindurch und an die Anode 25 eine gegenüber dem Erdpotential positive Spannung durch den Anschlussteil 31 hindurch angelegt wird. Im Innenraum der Röhre stellen sich dann Potentiallinien ein, wie sie z. B. durch die gestrichelten Linien 32 und 33 in Fig. 1 angedeutet sind. Infolge der Vertiefung 18 des Keramikisolators 13, welche mit Isoliermaterial 19 mit niedrigerer Dielektrizitätskonstante ausgefüllt ist, nehmen die Potentiallinien 32 im Bereich des Keramikisolators 13 einen von der achsparallelen Richtung abweichenden, divergierenden Verlauf an, und zwar derart, dass an der ebenen inneren Endfläche 34 des Keramikisolators 13 die zu den Potentiallinien 32 stets rechtwinklig stehenden elektrischen Feldvektoren 35 vom Keramikisolator 13 weg gegen den Innenraum der Röntgenröhre weisende Richtungen haben. Ähnlich hat die Vertiefung 28 des andern Keramikisolators 23, welche mit Isoliermaterial 29 mit niedrigerer Dielektrizitätskonstante ausgefüllt ist, zur Folge, dass die Potentiallinien 33 im Bereich des Keramikisolators 23 einen konvergierenden Verlauf annehmen und deshalb die elektrischen Feldvektoren 36 an der ebenen inneren Endfläche 37 des Keramikisolators 23 von diesem weg gegen das Innere der Röntgenröhre weisende Richtungen haben. Der Winkel zwischen den Feldvektoren 35 bzw. 36 einerseits und der inneren Endfläche 34 bzw. 37 des Keramikisolators 13 bzw. 23 anderseits ist durch den Unterschied der Dielektrizitätskonstanten des Keramikmaterials und des gummielastischen Isoliermaterials durch die radiale Breite und die achsiale Tiefe der Vertiefung 18 bzw. 28 und durch die Abmessungen des Keramikisolators 13 bzw. 23 bestimmt. Weil sowohl auf der Kathodenseite als auch der Anodenseite die elektrische Feldstärke ihrer Richtung nach von der dortigen inneren Endfläche des Keramikisolators 13 bzw. 23 weg ins Innere der Röntgenröhre weist, sind Aufladungen an den Keramikisolatoren 13 und 23 wie auch damit verbundene Feldstärkenüberhöhungen wirksam vermieden. Im Vergleich zu ähnlichen bekannten Röntgenröhren, bei denen die Keramikisolatoren jeweils ebene äussere Endflächen ohne die Stufen 17 und 27 aufweisen, hat die Röntgenröhre gemäss Fig. 1 eine merklich höhere Fugen-Spannungsfestigkeit.To operate the described X-ray tube, the metal part 11 is connected to earth potential, while a voltage which is negative with respect to the earth potential is applied to the cathode 15 through the connection part 21 and a voltage which is positive with respect to the earth potential is applied through the connection part 31 to the anode 25. In the interior of the tube, potential lines are then set, such as, for. B. are indicated by the dashed lines 32 and 33 in Fig. 1. As a result of the depression 18 of the ceramic insulator 13, which is filled with insulating material 19 with a lower dielectric constant, the potential lines 32 in the region of the ceramic insulator 13 assume a diverging profile that deviates from the axis-parallel direction, in such a way that on the flat inner end surface 34 of the Ceramic insulator 13 which have electrical field vectors 35, which are always at right angles to the potential lines 32, away from the ceramic insulator 13 against the interior of the X-ray tube. Similarly, the recess 28 of the other ceramic insulator 23, which is filled with insulating material 29 with a lower dielectric constant, has the result that the potential lines 33 in the area of the ceramic insulator 23 assume a converging course and therefore the electric field vectors 36 on the flat inner end surface 37 of the ceramic insulator 23 have directions pointing away from this towards the inside of the X-ray tube. The angle between the field vectors 35 and 36 on the one hand and the inner end surface 34 and 37 of the ceramic insulator 13 and 23 on the other hand is due to the difference in the dielectric constants of the ceramic material and the rubber-elastic insulating material due to the radial width and the axial depth of the recess 18 or 28 and determined by the dimensions of the ceramic insulator 13 or 23. Because both on the cathode side and on the anode side the electrical field strength points in their direction away from the inner end face of the ceramic insulator 13 and 23 into the interior of the X-ray tube, charges on the ceramic insulators 13 and 23 as well as the associated field strength increases are effectively avoided. In comparison to similar known X-ray tubes, in which the ceramic insulators each have flat outer end faces without the steps 17 and 27, the X-ray tube according to FIG. 1 has a noticeably higher joint dielectric strength.

Die geschilderten Vorteile wurden anhand einer Versuchs-Röntgenröhre überprüft und bestätigt gefunden. Die Versuchs- Röntgenröhre mit dem in Fig. 1 gezeigten Aufbau wies Keramikisolatoren 13 und 23 mit einem Aussendurchmesser von 107 mm, einem Innendurchmesser von 45 mm auf. Die achsiale Dickenabmessung der Keramikisolatoren betrug 10 mm und war an der Stelle der Vertiefung 18 bzw. 28 auf 7 mm reduziert, so dass die Stufe 17 bzw. 27 eine Höhe von 3 mm hatte. Die gummielastischen Ringscheiben 20 und 30 bestanden aus Silikonkautschuk mit einer Dielektrizitätskonstante von 3,2 und einer Shorehärte von 28. In unbelastetem Zustand waren die beiden achsialen Endflächen jeder gummielastischen Ringscheibe 20 bzw. 30 eben und parallel, und der Aussendurchmesser betrug 100 mm, der Innendurchmesser 45 mm und die achsiale Dicke 10 mm. Die Röntgenröhre liess sich problemlos mit einer Spannung bis zu 340 kV zwischen Anode und Kathode betreiben.The described advantages were checked and confirmed using a test X-ray tube. The experimental X-ray tube with the structure shown in FIG. 1 had ceramic insulators 13 and 23 with an outside diameter of 107 mm and an inside diameter of 45 mm. The axial thickness dimension of the ceramic insulators was 10 mm and was reduced to 7 mm at the location of the recess 18 or 28, so that the step 17 or 27 had a height of 3 mm. The rubber-elastic washers 20 and 30 were made of silicone rubber with a dielectric constant of 3.2 and a Shore hardness of 28. In the unloaded state, the two axial end faces of each rubber-elastic washer 20 and 30 were flat and parallel, and the outside diameter was 100 mm, the inside diameter 45 mm and the axial thickness 10 mm. The X-ray tube could easily be operated with a voltage of up to 340 kV between the anode and cathode.

Praktisch gleich gute Ergebnisse lassen sich erzielen, wenn die Keramikisolatoren etwa gemäss den in den Fig. 2 bis 5 gezeigten Ausführungsbeispielen geformt sind.Practically equally good results can be achieved if the ceramic insulators are shaped approximately according to the exemplary embodiments shown in FIGS. 2 to 5.

Der in Fig. 2 dargestellte Keramikisolator 113 für die Kathodenseite der Röntgenröhre weist an seiner nach aussen zu wendenden achsialen Endfläche 116 zwei in Umfangsrichtung verlaufende Stufen 117 auf, durch welche eine an den Aussenumfang des Keramikisolators angrenzende achsiale Vertiefung 118 gebildet ist.The ceramic insulator 113 shown in FIG. 2 for the cathode side of the X-ray tube has, on its axial end face 116 to be turned outwards, two steps 117 running in the circumferential direction, by means of which an axial recess 118 adjacent to the outer circumference of the ceramic insulator is formed.

Das in Fig. 3 gezeigte Beispiel eines Keramikisolators 213 für die Kathodenseite der Röntgenröhre weist an seiner nach aussen zu wendenden achsialen Endfläche 216 eine rampenförmige Abstufung 217 auf, durch die eine an den Aussenumfang des Keramikisolators angrenzende achsiale Vertiefung 218 gebildet ist.The example of a ceramic insulator 213 for the cathode side of the X-ray tube shown in FIG. 3 has a ramp-shaped step 217 on its axial end face 216 to be turned outwards, by means of which an axial recess 218 adjacent to the outer circumference of the ceramic insulator is formed.

Der in Fig. 4 gezeigte Keramikisolator 123 für die Anodenseite der Röntgenröhre weist an seiner nach aussen zu wendenden achsialen Endfläche 126 zwei in Umfangsrichtung verlaufende Stufen 117 auf, durch die eine an den Innenumfang des Keramikisolators angrenzende achsiale Vertiefung 128 gebildet ist.The ceramic insulator 123 shown in FIG. 4 for the anode side of the X-ray tube has two steps 117 running in the circumferential direction on its axial end face 126 to be turned outwards, by means of which an axial recess 128 adjacent to the inner circumference of the ceramic insulator is formed.

Gemäss Fig. 5 kann der Keramikisolator 223 für die Anodenseite der Röntgenröhre aber auch eine rampenförmige Abstufung 227 an der nach aussen zu wendenden achsialen Endfläche aufweisen, so dass eine an den inneren Umfang des Keramikisolators angrenzende achsiale Vertiefung 228 gebildet ist.5, the ceramic insulator 223 for the anode side of the X-ray tube can also have a ramp-shaped step 227 on the axial end face to be turned outwards, so that an axial recess 228 adjacent to the inner circumference of the ceramic insulator is formed.

Die Vertiefungen 118,218,128 und 228 der Keramikisolatoren 113, 213, 123 und 223 gemäss den Fig. 2 bis 5 werden beim Zusammenbau oder Einbau der Röntgenröhre jeweils mit gummielastischem Isoliermaterial, dessen Dielektrizitätskonstante kleiner als diejenige des Keramikmaterials ist, vollständig ausgefüllt.The depressions 118, 218, 128 and 228 of the ceramic insulators 113, 213, 123 and 223 according to FIGS. 2 to 5 are each made with rubber-elastic insulating material and its dielectric during assembly or installation of the X-ray tube constant is smaller than that of the ceramic material, completely filled.

Bekanntlich gibt es Röntgenröhren, bei denen die Kathode oder die Anode mit dem zylindrischen Metallteil elektrisch leitend verbunden ist. In einem solchen Fall ist jeweils nur die andere Elektrode Anode oder Kathode durch einen Keramikisolator von dem zylindrischen Metallteil isoliert. Die Erfindung ist auch bei solchen Röntgenröhren anwendbar, indem der dann einzige vorhandene Keramikisolator in der vorstehend beschriebenen Weise an seiner vom Innern der Röntgenröhre abgewandten achsialen Endfläche mit einer Vertiefung versehen ist, die vollständig ausgefüllt ist mit einem Isoliermaterial, dessen Dielektrizitätskonstante kleiner als diejenige des Keramikmaterials ist.As is known, there are X-ray tubes in which the cathode or the anode is electrically conductively connected to the cylindrical metal part. In such a case, only the other anode or cathode is insulated from the cylindrical metal part by a ceramic insulator. The invention is also applicable to such X-ray tubes in that the then only existing ceramic insulator in the manner described above is provided on its axial end surface facing away from the inside of the X-ray tube with a depression which is completely filled with an insulating material whose dielectric constant is smaller than that of the ceramic material is.

Claims (5)

1. X-ray tube with a cylindrical metal part surrounding the anode and the cathode, wherein at least one of the electrodes anode and cathode is electrically insulated from said metal part by a disk-shaped ceramic insulator which is located at an axial end of the metal part, characterized in thatthe disk-shaped ceramic insulator (13; 23; 113; 123; 213; 223) at its axial end (16; 26; 116; 216; 226) facing away from the interior of the X-ray tube is formed to be step-shaped or ramp-shaped in radial directions to create an annular axial depression (18; 28; 118; 128; 218; 228) which is filled with an insulating material (19; 29) having a dielectric constant lower than that of the ceramic material, and in that, in case of a ceramic insulator (13; 113; 213) which insulates the anode (25) from the metal part (11), the depression is located at a radially inner portion, while in case of a ceramic insulator (23; 123; 223) which insulates the cathode (15) from the metal part (11), the depression is located at a radially outer portion, so that in operation of the X-ray tube the electric field (35; 36) is deviated away from the inner end face (34; 37) of the ceramic insulator (13; 23; 113; 123; 213; 223) toward the interior of the X-ray tube and consequently a charge accumulation on the ceramic insulator surface is prevented.
2. X-ray tube according to claim 1, characterized in that the insulation material which fills the depression (18; 28; 118; 128; 218; 228) of the ceramic insulator (13; 23; 113; 123; 213; 223) is a portion (19; 29) of an elastic rubber disk (20; 30) which is pressed in axial direction against the step-shaped or ramp-shaped end face (16; 26; 116; 126; 216; 226) of the ceramic insulator.
3. X-ray tube according to claim 2, characterized in that the elastic rubber disk (20; 30) in relaxed condition has step-free axial end faces having about the same size as those of the ceramic insulator (13; 23; 113; 123; 213; 223).
4. X-ray tube according to any one of claims 1 to 3, characterized in that the insulation material (19; 29) which fills the depression (18; 28; 118; 128; 218; 228) is a silicone rubber having a dielectric constant of about 3.2.
5. X-ray tube according to any one of claims 1 to 4, wherein the anode and the cathode are each electrically insulated from the cylindrical metal part by a disk-shaped ceramic insulator, characterized in that each of the ceramic insulators (13; 23; 113; 123; 213; 223) at its axial end face (16; 26; 116; 126; 216; 226) which faces away from the interior of the X-ray tube is formed to be step-shaped or ramp-shaped in radial directions to create an annular axial depression (18; 28; 118; 128; 218; 228) which is filled with an insulation material (19; 29) having a dielectric constant lower than that of the ceramic material, and in that the depression (28; 128; 228) of the ceramic insulator (23; 123; 223) supporting the anode (25) is located at a radially inner portion, while the depression (18; 118; 218) of the ceramic insulator (13; 113; 213) supporting the cathode (15) is located at a radially outer portion.
EP86901329A 1985-03-28 1986-03-13 X-ray tube with a cylindrical metal component enclosing the anode and cathode Expired EP0215034B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT86901329T ATE40767T1 (en) 1985-03-28 1986-03-13 X-RAY TUBE WITH A CYLINDRICAL METAL PART SURROUNDING THE ANODE AND THE CATHODE.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH1363/85A CH665920A5 (en) 1985-03-28 1985-03-28 X-ray tube WITH THE ANODE AND CATHODE SURROUNDING CYLINDRICAL METAL PART.
CH1363/85 1985-03-28

Publications (2)

Publication Number Publication Date
EP0215034A1 EP0215034A1 (en) 1987-03-25
EP0215034B1 true EP0215034B1 (en) 1989-02-08

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ID=4208683

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Application Number Title Priority Date Filing Date
EP86901329A Expired EP0215034B1 (en) 1985-03-28 1986-03-13 X-ray tube with a cylindrical metal component enclosing the anode and cathode

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EP (1) EP0215034B1 (en)
JP (1) JPS62502796A (en)
AT (1) ATE40767T1 (en)
CH (1) CH665920A5 (en)
DE (1) DE3662079D1 (en)
WO (1) WO1986005921A1 (en)

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Publication number Priority date Publication date Assignee Title
DE19842467A1 (en) * 1998-09-16 2000-03-23 Siemens Ag Miniature X-ray tube for insertion into narrow objects, especially vessel systems in living tissue

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Publication number Priority date Publication date Assignee Title
DE4137804A1 (en) * 1991-11-16 1993-05-19 Licentia Gmbh High voltage X=ray tube - has annular grove in insulating annular disc, whose vacuum-side annular strip has annular gap
US7218707B2 (en) 2002-09-09 2007-05-15 Comet Holding Ag High-voltage vacuum tube
US7424095B2 (en) 2003-12-02 2008-09-09 Comet Holding Ag Modular X-ray tube and method of production thereof

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Publication number Priority date Publication date Assignee Title
DE6946926U (en) * 1969-12-03 1971-07-22 C H P Mueller Gmbh ROENTGE PIPE WITH METAL PISTON.
GB1458027A (en) * 1973-01-08 1976-12-08 Philips Electronic Associated Electric discharge vacuum tube
DE2506841C2 (en) * 1975-02-18 1986-07-03 Philips Patentverwaltung Gmbh, 2000 Hamburg High voltage vacuum tube
DE2747486A1 (en) * 1977-10-22 1979-04-26 Licentia Gmbh Small X=ray tube avoiding insulator charging - has vacuum vessel formed from metal part surrounding cathode and insulating cylinder around anode
DE2855905A1 (en) * 1978-12-23 1980-06-26 Licentia Gmbh DEVICE WITH A X-RAY TUBE
DE3116169A1 (en) * 1981-04-23 1982-11-11 Philips Patentverwaltung Gmbh, 2000 Hamburg HIGH VOLTAGE VACUUM TUBES, ESPECIALLY X-RAY TUBES

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19842467A1 (en) * 1998-09-16 2000-03-23 Siemens Ag Miniature X-ray tube for insertion into narrow objects, especially vessel systems in living tissue

Also Published As

Publication number Publication date
JPH0570897B2 (en) 1993-10-06
CH665920A5 (en) 1988-06-15
WO1986005921A1 (en) 1986-10-09
EP0215034A1 (en) 1987-03-25
DE3662079D1 (en) 1989-03-16
JPS62502796A (en) 1987-11-12
ATE40767T1 (en) 1989-02-15

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