US3890521A - X-ray tube target and X-ray tubes utilising such a target - Google Patents

X-ray tube target and X-ray tubes utilising such a target Download PDF

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US3890521A
US3890521A US318904A US31890472A US3890521A US 3890521 A US3890521 A US 3890521A US 318904 A US318904 A US 318904A US 31890472 A US31890472 A US 31890472A US 3890521 A US3890521 A US 3890521A
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carrier
target
layer
carbide
contact
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US318904A
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Arvind Shroff
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Thales SA
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Thomson CSF SA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H01J35/08—Anodes; Anti cathodes
    • H01J35/10—Rotary anodes; Arrangements for rotating anodes; Cooling rotary anodes
    • H01J35/108—Substrates for and bonding of emissive target, e.g. composite structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/08—Targets (anodes) and X-ray converters
    • H01J2235/083—Bonding or fixing with the support or substrate
    • H01J2235/084—Target-substrate interlayers or structures, e.g. to control or prevent diffusion or improve adhesion

Definitions

  • ABSTRACT relates to a graphite target for X-ray tubes.
  • the invention provides for the formation of the intermediate layer (2) in these targets, in the shape of two sub-layers one of which (20), in contact with the carrier, is made of a refractory material which does not form a carbide (iridium for example), and the other of which (21) is made of another refractory material (tantalum for example), which prevents diffusion of carbon from the carrier into the emissive layer.
  • the present invention relates to a target for X-ray tubes, more particularly a rotating target. and to the X-ray tubes utilising such a target.
  • Targets which are constituted by a carrier or base of graphite, to which there is applied an emissive layer producing an X-ray stream under the impact of electrons coming from the tube cathode.
  • tungsten is particularly advantageous and is often given preferencev
  • the object of the present invention is to improve targets of the kind hereinbefore described. More precisely, the invention relates to a target structure for X-ray tubes. on a graphite base, which prevents too rapid transformation to carbide on the part of the emissive layer and gives the tube a long surface life.
  • the invention provides for the arrangement between the carrier or base, and the emissive layer, of an intermediate layer made up of two sublayers as described hereinafter.
  • a target for X-ray tubes constituted by a carrier ofgraphite and an emissive layer made of a refractory metal having a high atomic number. covering said carrier and the two layers being separated by an intermediate layer. characterised in that said intermediate layer is constituted by two sub-layers one of which. that in contact with the carrier and referred to as the first sub-layer. is made of a refractory material which does not form a carbide and is in contact with the carrier, and the other of which. that is the second sub-layer. is in contact with the emissive layer and made of another refractory material.
  • the sublayer 20 is constituted by iridium, the sub-layer 21 by tantalum. and the emissive layer 3 by tungsten.
  • the adhesion of the tantalum carbide to the graphite is ensured because of the plasticity of the iridium sublayer which takes up the effect of the difference in coefficient of expansion.
  • a sub-layer 20 instead of iridium other elements such as osmium and ruthenium, and for the sub-layer 21, instead of tantalum, other elements such as hafnium, niobium or zirconium.
  • a target for X-ray tubes constituted by a carrier of graphite and an emissive layer made of tungsten covering said carrier and being separated by an intermediate layer, said intermediate layer is constituted by two sublayers one ofwhich is in contact the carrier and is made of an element selected from the group consisting essentially of iridium. osmium and ruthenium, and the other in contact with the emissive layer is made of an element selected from the group consisting essentially of hafnium, niobium. tantalum and zirconium.

Abstract

The present invention relates to a graphite target for X-ray tubes. In order to avoid the drawbacks of graphite carrier (1) targets due to transformation into carbide of the photo-emissive coating (3) by the carrier material, the invention provides for the formation of the intermediate layer (2) in these targets, in the shape of two sub-layers one of which (20), in contact with the carrier, is made of a refractory material which does not form a carbide (iridium for example), and the other of which (21) is made of another refractory material (tantalum for example), which prevents diffusion of carbon from the carrier into the emissive layer.

Description

D United States Patent 11 1 [111 3,890,521
Shroff 1 June 17, 1975 1 X-RAY TUBE TARGET AND X-RAY TUBES 3.649.355 3/1972 Hennig 313/330 UTILISING SUCH A TARGET 3,731,128 5/1973 Haberrecker 313/330 [75] Inventor: Arvind Shmfi Paris France Primary Examiner-Cameron K. Weiffenbach [73] Assignee: Thomson-CS1", Paris, France Attorney, Agent, or FirmRoland Plottel, Esq.
[22] Filed: Dec. 27, 1972 Appl; No.: 318,904
Foreign Application Priority Data Dec. 31, 1971 France 71.47766 References Cited UNITED STATES PATENTS 3/1970 Clement et al. 117/217 [57] ABSTRACT The present invention relates to a graphite target for X-ray tubes. In order to avoid the drawbacks of graphite carrier (1) targets due to transformation into carbide of the photo-emissive coating (3) by the carrier material, the invention provides for the formation of the intermediate layer (2) in these targets, in the shape of two sub-layers one of which (20), in contact with the carrier, is made of a refractory material which does not form a carbide (iridium for example), and the other of which (21) is made of another refractory material (tantalum for example), which prevents diffusion of carbon from the carrier into the emissive layer.
2 Claims, 1 Drawing Figure X-RAY TUBE TARGET AND X-RAY TUBES UTILISING SUCH A TARGET BACKGROUND OF THE INVENTION a. Field of the Invention The present invention relates to a target for X-ray tubes, more particularly a rotating target. and to the X-ray tubes utilising such a target.
b. Discussion of the Prior Art Targets are known which are constituted by a carrier or base of graphite, to which there is applied an emissive layer producing an X-ray stream under the impact of electrons coming from the tube cathode.
Amongst the various elements of high atomic number which can be used for the emissive layer. tungsten is particularly advantageous and is often given preferencev However, a tungsten layer applied directly to the graphite carrier. at the temperatures encountered during operation. undergoes a chemical reaction with the carbon of the carrier and is quickly transformed to tungsten carbide throughout its thickness; the carbide layer thus formed becomes detached from the carrier.
Solutions which are designed to overcome this drawback. are already known from the prior art.
Thus. it has been proposed that there be arranged be tween the carrier and the tungsten layer. an intermediate tantalum layer which is transformed to a carbide; the layer of tantalum carbide thus formed prevents diffusion of the carbon and thus prevents the formation of tungsten carbide. However. the fragility ofthe tantalum carbide means that the assembly becomes detached from the carrier because of the differences in coeffcient of expansion. Again, it has been proposed that an intermediate layer of rhenium be used. Rhenium does not form a carbide but. with carbon and at 2480C, it forms a eutectic structure containing 16.9 carbon atoms percent. Tungsten carbide forms by contact between the tungsten and this carbide-rich alloy. The rhenium layer is therefore ineffective in preventing the formation of tungsten carbide.
SUMMARY OF THE INVENTION The object of the present invention is to improve targets of the kind hereinbefore described. More precisely, the invention relates to a target structure for X-ray tubes. on a graphite base, which prevents too rapid transformation to carbide on the part of the emissive layer and gives the tube a long surface life.
To this end, the invention provides for the arrangement between the carrier or base, and the emissive layer, of an intermediate layer made up of two sublayers as described hereinafter.
According to the invention there is provided a target for X-ray tubes, constituted by a carrier ofgraphite and an emissive layer made of a refractory metal having a high atomic number. covering said carrier and the two layers being separated by an intermediate layer. characterised in that said intermediate layer is constituted by two sub-layers one of which. that in contact with the carrier and referred to as the first sub-layer. is made of a refractory material which does not form a carbide and is in contact with the carrier, and the other of which. that is the second sub-layer. is in contact with the emissive layer and made of another refractory material.
BRIEF DESCRIPTION OF THE DRAWING The single FIGURE illustrates an embodiment of a target in accordance with the invention:
DESCRIPTION OF THE PREFERRED EMBODIMENTS On a graphite carrier 1, there are successively deposited a sub-layer 20 ofa refractory metal which does not form a carbide and then, on this first sub-layer, a second sub-layer 21 of another refractory metal. These two sub-layers constitute the intermediate layer 2. On this latter, there is then deposited the emissive layer of refractory metal, 3.
In a preferred embodiment of the invention, the sublayer 20 is constituted by iridium, the sub-layer 21 by tantalum. and the emissive layer 3 by tungsten.
These different metals are deposited upon the carrier 1 by any known prior art method, for example:
in the case of iridium, by cathode-sputtering to a thickness of around 50 am;
in the case of tantalum, by chemical reaction in the vapour phase, between the chloride and a hydrogen flow at a temperature T at least equal to [000 C and at a pressure P of less than or equal to l torr, this in order to avoid any hydride formation; an example of the conditions employed is given below:
P l torr T 1 C Tun-ls hydrogen flow I00 cm lmn thickness of deposit: 50 am in the case of tungsten, by chemical reaction of the gaseous fluoride with a hydrogen fow, under the following conditions:
P lO' torr T l300C Ratio H /WF 3 thickness of the layer: 500 um During the initial operation of the tube, carbon diffuses across the iridium and reacts with the tantalum, transforming the tantalum to tantalum carbide which will not allow the diffusion of carbon and prevents the formation of tungsten carbide.
The adhesion of the tantalum carbide to the graphite is ensured because of the plasticity of the iridium sublayer which takes up the effect of the difference in coefficient of expansion.
In other variant embodiments, it is possible to use a sub-layer 20, instead of iridium other elements such as osmium and ruthenium, and for the sub-layer 21, instead of tantalum, other elements such as hafnium, niobium or zirconium.
Of course. the invention is not limited to the embodiment described and shown which was given solely by way of example.
What we claim is:
l. A target for X-ray tubes constituted by a carrier of graphite and an emissive layer made of tungsten covering said carrier and being separated by an intermediate layer, said intermediate layer is constituted by two sublayers one ofwhich is in contact the carrier and is made of an element selected from the group consisting essentially of iridium. osmium and ruthenium, and the other in contact with the emissive layer is made of an element selected from the group consisting essentially of hafnium, niobium. tantalum and zirconium.
till
contact with the carrier and is made of an element scluctutl from the group cunsisting Essentially of iridium, osmium, and ruthenium, and the other is in contact with the emissivc layer is mudc of an element selected from the group consisting essentially of hafnium. nio-

Claims (2)

1. A TARGET FOR X-RAY TUBES CONSTITUTED BY A CARRIER OF GRAPHITE AND AN EMISSIVE LAYER MADE OF TUNGSTEN COVERING SAID CARRIER AND BEING SEPARATED BY AN INTERMEDIATE LAYER, SAID INTERMEDIATE LAYER IS CONSTITUTED BY TWO SUB-LAYERS ONE OF WHICH IS IS CONTACT THE CARRIER AND IS MADE OF AN ELEMENT SELECTED FROM THE GROUP CONSISTING ESSENTIALLY OF IRIDIUM OSMIUM AND RUTHENIUM, AND THE OTHER IN CONTACT WITH THE EMISSIVE LAYER IS MADE
2. An X-ray tube comprising target means for producing X-rays when impacted by electrons, cathode means for generating electrons, said target means including a carrier of graphite and an emissive layer made of tungsten covering said carrier and being separated by an intermediate layer, said intermediate layer is constituted by two sub-layers, one of which is in contact with the carrier and is made of an element selected from the group consisting essentially of iridium, osmium, and ruthenium, and the other is in contact with the emissive layer is made of an element selected from the group consisting essentIally of hafnium, niobium, tantalum, and zirconium.
US318904A 1971-12-31 1972-12-27 X-ray tube target and X-ray tubes utilising such a target Expired - Lifetime US3890521A (en)

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DE (1) DE2263820A1 (en)
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Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4119879A (en) * 1977-04-18 1978-10-10 General Electric Company Graphite disc assembly for a rotating x-ray anode tube
US4145632A (en) * 1977-04-18 1979-03-20 General Electric Company Composite substrate for rotating x-ray anode tube
US4227112A (en) * 1978-11-20 1980-10-07 The Machlett Laboratories, Inc. Gradated target for X-ray tubes
EP0023065A1 (en) * 1979-07-19 1981-01-28 Philips Patentverwaltung GmbH Rotary anode for X-ray tubes
US4266138A (en) * 1978-07-11 1981-05-05 Cornell Research Foundation, Inc. Diamond targets for producing high intensity soft x-rays and a method of exposing x-ray resists
USRE31369E (en) * 1977-04-18 1983-09-06 General Electric Company Method for joining an anode target comprising tungsten to a graphite substrate
USRE31560E (en) * 1977-04-18 1984-04-17 General Electric Company Graphite disc assembly for a rotating x-ray anode tube
USRE31568E (en) * 1977-04-18 1984-04-24 General Electric Company Composite substrate for rotating x-ray anode tube
US4597095A (en) * 1984-04-25 1986-06-24 General Electric Company Composite structure for rotating anode of an X-ray tube
US4641334A (en) * 1985-02-15 1987-02-03 General Electric Company Composite rotary anode for X-ray tube and process for preparing the composite
US4645121A (en) * 1985-02-15 1987-02-24 General Electric Company Composite rotary anode for X-ray tube and process for preparing the composite
US4670895A (en) * 1984-06-29 1987-06-02 Thomson-Cgr X-ray tube with a rotary anode and process for fixing a rotary anode to a support shaft
FR2593324A1 (en) * 1986-01-17 1987-07-24 Thomson Cgr ROTATING ANODE WITH GRAPHITE FOR RADIOGENE TUBE
US4689810A (en) * 1985-02-15 1987-08-25 General Electric Company Composite rotary anode for X-ray tube and process for preparing the composite
EP0249141A2 (en) * 1986-06-13 1987-12-16 General Electric Company X-ray tube target
US4777643A (en) * 1985-02-15 1988-10-11 General Electric Company Composite rotary anode for x-ray tube and process for preparing the composite
US5204891A (en) * 1991-10-30 1993-04-20 General Electric Company Focal track structures for X-ray anodes and method of preparation thereof
US5222116A (en) * 1992-07-02 1993-06-22 General Electric Company Metallic alloy for X-ray target
WO1994023458A2 (en) * 1993-04-05 1994-10-13 Cardiac Mariners, Inc. X-ray detector for a low dosage scanning beam digital x-ray imaging system
US5550378A (en) * 1993-04-05 1996-08-27 Cardiac Mariners, Incorporated X-ray detector
US5610967A (en) * 1993-01-25 1997-03-11 Cardiac Mariners, Incorporated X-ray grid assembly
US5682412A (en) * 1993-04-05 1997-10-28 Cardiac Mariners, Incorporated X-ray source
WO1998011592A1 (en) * 1996-09-13 1998-03-19 Varian Associates, Inc. X-ray target having high z particles imbedded in a matrix
US9053897B2 (en) 2010-12-16 2015-06-09 Koninklijke Philips N.V. Anode disk element with refractory interlayer and VPS focal track

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4073426A (en) * 1977-04-18 1978-02-14 General Electric Company Method for joining an anode target comprising tungsten to a graphite substrate
FR2535344A1 (en) * 1982-10-29 1984-05-04 Thomson Csf METHOD FOR SELECTIVE DEPOSITION OF A REFRACTORY METAL LAYER ON A GRAPHITE PIECE
AT392760B (en) * 1989-05-26 1991-06-10 Plansee Metallwerk COMPOSITE BODY MADE OF GRAPHITE AND HIGH-MELTING METAL
US6118853A (en) * 1998-10-06 2000-09-12 Cardiac Mariners, Inc. X-ray target assembly
DE102009033607A1 (en) * 2009-07-17 2011-01-20 Siemens Aktiengesellschaft Anode for X-ray tube of imaging X-ray device, has barrier layer arranged between carrier and emitter layer and made from material e.g. rhenium, osmium or hafnium, where anode is arranged above X-ray radiation emitting window

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US3504327A (en) * 1965-06-14 1970-03-31 Sfec Heater element
US3649355A (en) * 1968-08-12 1972-03-14 Schwarzopf Dev Corp Process for production of rotary anodes for roentgen tubes
US3731128A (en) * 1972-03-08 1973-05-01 Siemens Ag X-ray tube with rotary anodes

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Publication number Priority date Publication date Assignee Title
US3504327A (en) * 1965-06-14 1970-03-31 Sfec Heater element
US3649355A (en) * 1968-08-12 1972-03-14 Schwarzopf Dev Corp Process for production of rotary anodes for roentgen tubes
US3731128A (en) * 1972-03-08 1973-05-01 Siemens Ag X-ray tube with rotary anodes

Cited By (35)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE31369E (en) * 1977-04-18 1983-09-06 General Electric Company Method for joining an anode target comprising tungsten to a graphite substrate
US4145632A (en) * 1977-04-18 1979-03-20 General Electric Company Composite substrate for rotating x-ray anode tube
US4119879A (en) * 1977-04-18 1978-10-10 General Electric Company Graphite disc assembly for a rotating x-ray anode tube
USRE31568E (en) * 1977-04-18 1984-04-24 General Electric Company Composite substrate for rotating x-ray anode tube
USRE31560E (en) * 1977-04-18 1984-04-17 General Electric Company Graphite disc assembly for a rotating x-ray anode tube
US4266138A (en) * 1978-07-11 1981-05-05 Cornell Research Foundation, Inc. Diamond targets for producing high intensity soft x-rays and a method of exposing x-ray resists
US4227112A (en) * 1978-11-20 1980-10-07 The Machlett Laboratories, Inc. Gradated target for X-ray tubes
US4352041A (en) * 1979-07-19 1982-09-28 U.S. Philips Corporation Rotary anodes for X-ray tubes
EP0023065A1 (en) * 1979-07-19 1981-01-28 Philips Patentverwaltung GmbH Rotary anode for X-ray tubes
US4597095A (en) * 1984-04-25 1986-06-24 General Electric Company Composite structure for rotating anode of an X-ray tube
US4670895A (en) * 1984-06-29 1987-06-02 Thomson-Cgr X-ray tube with a rotary anode and process for fixing a rotary anode to a support shaft
US4777643A (en) * 1985-02-15 1988-10-11 General Electric Company Composite rotary anode for x-ray tube and process for preparing the composite
US4641334A (en) * 1985-02-15 1987-02-03 General Electric Company Composite rotary anode for X-ray tube and process for preparing the composite
US4645121A (en) * 1985-02-15 1987-02-24 General Electric Company Composite rotary anode for X-ray tube and process for preparing the composite
US4689810A (en) * 1985-02-15 1987-08-25 General Electric Company Composite rotary anode for X-ray tube and process for preparing the composite
FR2593324A1 (en) * 1986-01-17 1987-07-24 Thomson Cgr ROTATING ANODE WITH GRAPHITE FOR RADIOGENE TUBE
EP0234967A1 (en) * 1986-01-17 1987-09-02 General Electric Cgr S.A. Rotating anode with graphite for X-ray tube
US4799250A (en) * 1986-01-17 1989-01-17 Thomson-Cgr Rotating anode with graphite for X-ray tube
EP0249141A2 (en) * 1986-06-13 1987-12-16 General Electric Company X-ray tube target
EP0249141A3 (en) * 1986-06-13 1988-07-13 General Electric Company X-ray tube target
US5204891A (en) * 1991-10-30 1993-04-20 General Electric Company Focal track structures for X-ray anodes and method of preparation thereof
US5222116A (en) * 1992-07-02 1993-06-22 General Electric Company Metallic alloy for X-ray target
US5751785A (en) * 1993-01-25 1998-05-12 Cardiac Mariners, Inc. Image reconstruction methods
US5610967A (en) * 1993-01-25 1997-03-11 Cardiac Mariners, Incorporated X-ray grid assembly
US5644612A (en) * 1993-01-25 1997-07-01 Cardiac Mariners, Inc. Image reconstruction methods
US5651047A (en) * 1993-01-25 1997-07-22 Cardiac Mariners, Incorporated Maneuverable and locateable catheters
US5729584A (en) * 1993-01-25 1998-03-17 Cardiac Mariners, Inc. Scanning-beam X-ray imaging system
US5835561A (en) * 1993-01-25 1998-11-10 Cardiac Mariners, Incorporated Scanning beam x-ray imaging system
US5859893A (en) * 1993-01-25 1999-01-12 Cardiac Mariners, Inc. X-ray collimation assembly
WO1994023458A3 (en) * 1993-04-05 1994-11-10 Wilent Virginia & Hf X-ray detector for a low dosage scanning beam digital x-ray imaging system
US5550378A (en) * 1993-04-05 1996-08-27 Cardiac Mariners, Incorporated X-ray detector
US5682412A (en) * 1993-04-05 1997-10-28 Cardiac Mariners, Incorporated X-ray source
WO1994023458A2 (en) * 1993-04-05 1994-10-13 Cardiac Mariners, Inc. X-ray detector for a low dosage scanning beam digital x-ray imaging system
WO1998011592A1 (en) * 1996-09-13 1998-03-19 Varian Associates, Inc. X-ray target having high z particles imbedded in a matrix
US9053897B2 (en) 2010-12-16 2015-06-09 Koninklijke Philips N.V. Anode disk element with refractory interlayer and VPS focal track

Also Published As

Publication number Publication date
GB1385350A (en) 1975-02-26
FR2166625A5 (en) 1973-08-17
DE2263820A1 (en) 1973-07-05

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