EP0235619B1 - Cathode à incandescence pour tube à rayons X - Google Patents

Cathode à incandescence pour tube à rayons X Download PDF

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Publication number
EP0235619B1
EP0235619B1 EP87101758A EP87101758A EP0235619B1 EP 0235619 B1 EP0235619 B1 EP 0235619B1 EP 87101758 A EP87101758 A EP 87101758A EP 87101758 A EP87101758 A EP 87101758A EP 0235619 B1 EP0235619 B1 EP 0235619B1
Authority
EP
European Patent Office
Prior art keywords
ray tube
tungsten
layers
glow cathode
band emitter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP87101758A
Other languages
German (de)
English (en)
Other versions
EP0235619A1 (fr
Inventor
Hannjörg Dipl.-Phys. Bittorf
Willibald Dipl.-Phys. Knott
Herbert Dipl.-Phys. Schnitger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP0235619A1 publication Critical patent/EP0235619A1/fr
Application granted granted Critical
Publication of EP0235619B1 publication Critical patent/EP0235619B1/fr
Expired legal-status Critical Current

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Classifications

    • 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
    • H01J35/06—Cathodes
    • H01J35/064—Details of the emitter, e.g. material or structure

Definitions

  • the invention relates to an X-ray tube hot cathode with an electrically heated band emitter provided with at least one slot, which consists of electron-emissive, difficult to melt material.
  • DE-OS 27 27 907 such a band emitter is described, which is heated by direct electrical current passage. This is made of sheet metal and has incisions in the emission area from opposite sides. This allows any shape of the emitter surface to be achieved in a simple manner and also certain desirable temperature distributions in the surface.
  • band emitters show susceptibility to breakage at the grain boundaries, which run transverse to the slot direction of the band emitter. Because of the small thickness of the band material, the grain boundaries extend over the entire material thickness after recrystallization of, for example, tungsten, so that band emitters of this type are very sensitive and have a short service life. When using tantalum, the susceptibility to breakage decreases significantly; but the mechanical stability is reduced. This means that the emitters can warp.
  • the invention is based on the object of creating an X-ray tube hot cathode of the type mentioned at the outset, which has increased mechanical stability and an improved service life.
  • the band emitter is constructed from at least two layers. It is thereby achieved that the grain boundaries do not continue at the border crossing between the two layers, so that the risk of breakage for the band emitter along such grain boundaries, which are expressed over the entire material thickness, is considerably reduced.
  • one layer consists of tungsten and at least one further layer consists of tantalum.
  • the favorable elastic properties of tantalum further reduce the risk of breakage, while the mechanical stability of tungsten ensures that the shape remains true.
  • the band emitter has three layers, the middle layer consisting of tungsten and the two outer layers consisting of tantalum.
  • the layers of the band emitter consist of different structures of the same material. This ensures that the grain boundaries at the boundary layer of different structures of the same material do not continue.
  • one layer consists of normally structured tungsten and at least one further layer consists of polycrystalline tungsten.
  • a particularly stable structure is achieved if the band emitter has three layers, the middle layer consisting of normally structured tungsten and the outer layers consisting of polycrystalline tungsten. The stability of the carrier layer is increased if the middle layer has a greater thickness than the outer layers.
  • the cathode arrangement 3 has an extension 6 on its housing 5, which contains a band emitter 7 as a hot cathode, which lies within a focusing device 8.
  • the actual anode 9, which is designed as a rotating anode, is located opposite the cathode arrangement 3.
  • a heating voltage is applied to the ends 10 and 11 of the band emitter 7 via lines 16 and 18.
  • the actual operating voltage i.e., the line 16 and a connecting piece 12 located at the anode-side end of the X-ray tube 2.
  • the acceleration voltage for the electrons emerging from the hot cathode corresponding to the dashed line 13 is applied.
  • the focusing device 8 is set to emitter potential by means of a bridging line 17.
  • the band emitter 7 is shown in FIG. It consists, for example, of a 0.05 mm thick, band-shaped sheet and has a side length of, for example, 3 mm x 8 mm.
  • the sheet is cut from both sides with slots 14 and 15 such that the respective cuts end as far away from the opposite boundary of the sheet as the slots 14 and 15 are laterally spaced apart.
  • the ends 10 and 11 are attached for connecting the heating voltage.
  • FIG. 3 shows a further embodiment of the band emitter 7, in which the part to be heated consists of a 2 mm ⁇ 1.2 mm sheet which has a slot 19.
  • the ends 10 and 11 are arranged for connecting the heating voltage.
  • Such a narrow band emitter 7 generates a small focal spot, as is required, for example, for X-ray fluoroscopy.
  • the two band emitters 7 of FIGS. 2 and 3 can be arranged next to one another in the cathode arrangement 3 and can be connected to the heating voltage as required.
  • a band emitter 7 constructed in this way, as shown in cross section in FIG. 4, according to the invention consists of three layers.
  • the inner one Layer 20 consists, for example, of 50 J.1 m thick tungsten, which is surrounded by two layers 21 and 22 made of, for example, 10 J.1 m thick tantalum.
  • the production of the band material required for the band emitter 7 can be produced by rolling out a blank produced by metallurgy or by subsequent coating by means of sputtering, CVD, or by ion implantation of heavy metals.
  • This arrangement with an outer tantalum coating gives the advantage in operation that the hot cathode can be operated at a low temperature because of the low work function of tantalum. As a result, the recrystallization of the tungsten core proceeds more slowly, so that the durability of such a hot cathode is further increased.
  • the band emitter 7 can also consist of a different structure of the same material.
  • the inner layer 20 can be made of normally structured tungsten and the outer layers 21 and 22 can be made of polycrystalline tungsten.

Landscapes

  • Solid Thermionic Cathode (AREA)

Claims (7)

1. Cathode incandescente pour tube à rayons X, comprenant un émetteur en bande, chauffé électriquement et pourvu d'au moins une fente, qui est réalisé en matériau capable d'émettre des électrons et difficilement fusible, caractérisée en ce que l'émetteur en bande (7) est constitué d'au moins deux couches (20 à 22).
2. Cathode selon la revendication 1, caractérisée en ce que l'une (20) des couches est en tungstène et au moins une autre couche (21, 22) est en tantale.
3. Cathode selon la revendication 2, caractérisée en ce que l'émetteur en bande (7) comporte trois couches (20 à 22%) dont celle (20) du milieu est en tungstène et dont les deux couches extérieures (21, 22) sont en tantale.
4. Cathode selon la revendication 1, caractérisée en ce que les couches (20 à 22) de l'émetteur en bande (7) sont formées de textures différentes du même matériau.
5. Cathode selon la revendication 4, caractérisée en ce qu'une couche (20) est en tungstène à structure normale et au moins une autre couche (21, 22) est en tungstène polycristallin.
6. Cathode selon la revendication 5, caractérisée en ce que l'émetteur en bande (7) comporte trois couches (20 à 22) dont la couche du milieu est en tungstène à structure normale et les couches extérieures (21, 22) sont en tungstène polycristallin.
7. Cathode selon la revendication 3 ou 6, caractérisée en ce que la couche (20) du milieu possède une plus grande épaisseur que les couches extérieures (21, 22).
EP87101758A 1986-02-21 1987-02-09 Cathode à incandescence pour tube à rayons X Expired EP0235619B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3605540 1986-02-21
DE3605540 1986-02-21

Publications (2)

Publication Number Publication Date
EP0235619A1 EP0235619A1 (fr) 1987-09-09
EP0235619B1 true EP0235619B1 (fr) 1989-08-16

Family

ID=6294587

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87101758A Expired EP0235619B1 (fr) 1986-02-21 1987-02-09 Cathode à incandescence pour tube à rayons X

Country Status (3)

Country Link
EP (1) EP0235619B1 (fr)
JP (1) JPS62135347U (fr)
DE (1) DE3760462D1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102014211688A1 (de) 2014-06-18 2015-12-24 Siemens Aktiengesellschaft Flachemitter

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6259193B1 (en) 1998-06-08 2001-07-10 General Electric Company Emissive filament and support structure
FR2863769B1 (fr) * 2003-12-12 2006-03-24 Ge Med Sys Global Tech Co Llc Procede de fabrication d'un filament de cathode d'un tube a rayons x et tube a rayons x
US7693265B2 (en) * 2006-05-11 2010-04-06 Koninklijke Philips Electronics N.V. Emitter design including emergency operation mode in case of emitter-damage for medical X-ray application
US8183756B2 (en) 2007-07-24 2012-05-22 Koninklijke Philips Electronics Nv Thermionic electron emitter, method for preparing same and X-ray source including same
US8385506B2 (en) * 2010-02-02 2013-02-26 General Electric Company X-ray cathode and method of manufacture thereof
DE102015215690A1 (de) 2015-08-18 2017-03-09 Siemens Healthcare Gmbh Emitteranordnung

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2256297A (en) * 1939-08-31 1941-09-16 Rca Corp Electron discharge device
GB1011398A (en) * 1963-01-22 1965-11-24 M O Valve Co Ltd Improvements in or relating to thermionic cathodes
NL7314131A (nl) * 1973-10-15 1975-04-17 Philips Nv Draaianode roentgenbuis.
DE2727907A1 (de) * 1977-06-21 1979-01-18 Siemens Ag Roentgenroehren-gluehkathode
JPS5568056A (en) * 1978-11-17 1980-05-22 Hitachi Ltd X-ray tube

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102014211688A1 (de) 2014-06-18 2015-12-24 Siemens Aktiengesellschaft Flachemitter

Also Published As

Publication number Publication date
JPS62135347U (fr) 1987-08-26
DE3760462D1 (en) 1989-09-21
EP0235619A1 (fr) 1987-09-09

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