US3821581A - Targets for x ray tubes - Google Patents

Targets for x ray tubes Download PDF

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Publication number
US3821581A
US3821581A US00168330A US16833071A US3821581A US 3821581 A US3821581 A US 3821581A US 00168330 A US00168330 A US 00168330A US 16833071 A US16833071 A US 16833071A US 3821581 A US3821581 A US 3821581A
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US
United States
Prior art keywords
target
wire
ray tube
set forth
winding
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 - Lifetime
Application number
US00168330A
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English (en)
Inventor
W Holland
T Koller
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.)
Varian Medical Systems Inc
Original Assignee
Machlett Laboratories Inc
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 Machlett Laboratories Inc filed Critical Machlett Laboratories Inc
Priority to US00168330A priority Critical patent/US3821581A/en
Priority to GB3312872A priority patent/GB1359121A/en
Priority to CH1137572A priority patent/CH567334A5/xx
Priority to FR7227674A priority patent/FR2148146B1/fr
Priority to DE2237855A priority patent/DE2237855C3/de
Priority to JP47076989A priority patent/JPS5214079B2/ja
Application granted granted Critical
Publication of US3821581A publication Critical patent/US3821581A/en
Assigned to VARIAN ASSOCIATES, INC., A DE CORP. reassignment VARIAN ASSOCIATES, INC., A DE CORP. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: MACHLETT LABORATORIES
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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

Definitions

  • An X-ray tube including a target structure having a focal area for receiving electrons from an adjacent cathode and generating X-radiation in response thereto, the focal area being provided with a surface designed to improve thermal properties such as by covering with a closely packed wrapping of relatively fine wire, the focal area preferably being a wirewrapped annulus sandwiched between two discs of high thermal conductivity material.
  • portion of the target which is to be subjected to elecseriously damaged through high thermal gradients causing severe mechanical stresses which result from bombardment by high energy electrons. This produces cracking, warping, and focal area disruption.
  • the temperature assumed by a conventional tungsten target at the focal spot may approach 3,400C and such heat may create hoop stresses which produce cracking, resulting in mechanical failure, or warpage which alters the target angle and thereby changes the focal spot size.
  • a target of a selected refractory base material having high thermal capacity such as molybdenum or graphite, for example.
  • a layer of high atomic number material which has high melting point and low vapor pressure.
  • This layer which may be vapor deposited, flame sprayed, or brazed, may cover one side of the base or may cover the entire base surface.
  • Such materials as rhenium, tungsten, or suitable alloys are deposited in the selected area or areas and are attached by a metallurgical bond to the base material.
  • a novel target structure which comprises a focal area which is provided with a surface of increased area for improved thermal properties, such being achieved by locating on the surface a layer of relatively fine closely packed wires. This may be done, for example, by wrapping the entire focal area in a wire winding.
  • the target comprises a disc having an inclined annular focal track defining a portion of a cone.
  • This focal track is covered by wires disposed in close side-by-side relation and extending along the generatrices of the cone in accordance with this invention.
  • generatrices is meant lines extending radially from the tip of the geometric cone to points on the outer periphery of the cone.
  • the annular focal track area may comprise a portion of a one-piece solid disc or, preferably will comprise a separate annulus or ring having the wire wrapped around it, the ring thereafter being sandwiched between two discs of high thermal conductivity material.
  • the focal area may be any suitable refractory material such as tungsten or tungsten-rhenium alloy, for example.
  • the supporting discs may be any refractory material such as molybdenum, titanium or graphite, for example.
  • the target In a fixed anode tube, the target may comprise a wire-wrapped disc inset into a block of copper or the like.
  • the rotating anode may be basically constructed as shown and described in US. patent application Ser. No. 230,053, filed Feb. 28, I972.
  • FIG. 1 is an axial section through an X-ray tube of the rotating anode type showing a target structured in ac cordance with this invention
  • FIG. 2 is an elevational view of the target in the tube of FIG. 1;
  • FIG. 3 is an axial section through the target of FIG. 2;
  • FIG. 4 is an enlarged view of a portion of the target of FIG. 3;
  • FIG. 5 is ,an enlarged elevational view of a portion of a target focal track
  • FIG. 6 is a diagram illustrating an electron beam impinging upon a target
  • FIG. 7 is a fragmentary elevational view of a modified rotating anode target
  • FIG. 8 is a fragmentary axial sectional view of the target shown in FIG. 7, and
  • FIG. 9 is a fragmentary axial sectional view of a portion of a stationary anode X-ray tube having a target embodying the present invention.
  • FIG. 1 an axial sectional viewof an X-ray tube of the rotating anode type which embodies a dielectric envelope 10 in which is supported an anode l2 and a cathode 14.
  • the cathode 14 includes a supporting cylinder 16 one end of which is sealed to a reentrant end portion 18 of the envelope.
  • On the inner end of cylinder 16 is mounted one end of a transversely extending angled support bracket 20, in the free end of which is located a cathode head 22.
  • the cathode head 22 contains an electron-emitting filament (see FIG. 3) to which a suitable electrical potential is applied through leads 24 extending externally of the tube through cylinder 16.
  • the opposite end of the envelope 10 carries the anode 12 which includes a target 26 mounted on one end of a rotor shaft 28 extending from a rotor 30 rotatably located in a neck portion 32 of the envelope.
  • the rotor carries a skirt 34 bolted thereto, and the assembly is adaptedto rotate rapidly when the tube is mounted in suitable inductive means surrounding the neck 32 when the inductive means is energized.
  • the anode target assembly comprises a focal track member 36 in the form' of a ring made of suitable high atomic number material, such refractory materials as tungsten or tungsten-rhenium being particularly suitable.
  • the focal track member 36 produces X-rays when bombarded by electrons from the cathode 22 in the usual manner of X-ray generators.
  • the exposed surface or track of the focal target member 36 is inclined so that X-rays will pass from the surface out of the tube through the side wall of the envelope. This surface defines a portion of a cone having its longitudinal axis coincident with the axis of the target 26 and particularly of the rotor shaft 28.
  • the target 26 is preferably made of a plurality of superimposed members as described in the aforementioned US. application Ser. No. 230,053.
  • the focal track member comprises a ring 36 having its lower side positioned upon a surface of a backing disc 38, which surface is shaped to receive the adjacent surface of the focal track ring.
  • the disc 38 is provided with a peripheral groove 40 in its upper surface within which the ring is nested.
  • the upper surface of the focal track ring 36 is provided with a circumferential ridge 42 which inclines on either side thereof to form first and second or inner and outer inclined surfaces 44 and 46 respectively.
  • Outer surface 44 is the exposed focal track surface and is at an appropriate predetermined angle to provide proper focal spot size, as will be described.
  • the inner surface 46 is inclined so as to effectively produce an annular recess within which a second backing ring or dome 48 is nested in a manner which permits thermal expansion and contraction between the parts without damage.
  • a nested structure of this type the focal track ring 36 is firmly engaged by adjacent surfaces of the backing disc 38 and dome 48 throughout relatively expansive surface areas to achieve efficient conduction of heat from disc or ring 36 to the disc 38 and the dome 48 as is desired.
  • the second backing ring or dome 48 is then mounted on the shaft 28 and slid down into intimate physical contact with the adjacent inclined surface 46 of ring 36, and the complete assembly is compactly and firmly pressed into an assembled unit by means such as a nut 52 which is threaded onto the end of the shaft into engagement with a cup-shaped retainer 54 carried by the second backing ring or dome 48, as illustrated.
  • X-ray tube anodes have a limited high load capability determined by the electron beam current density, among other parameters. At sufficiently high current densities even rotating anodes have been found to produce some surface melting and this, therefore, requires that limits be set on X-ray pulse duration and intensity of tube loading. Heat dissipation in X-ray anodes is accomplished primarily through radiation.
  • FIGS. 2-6 wherein the focal track ring 36 is fabricated with a closely packed wrapping of wire formed of suitable target material such as tungsten, rhenium-tungsten alloy or molybdenum, for example.
  • the wire 60 is tightly wrapped throughout the annulus of the ring 36 so that the individual turns extend substantially radially from the geometric center of the ring.
  • the wire 60 is preferably of a diameter selected in accordance with the size of the focal spot which is to be produced by the tube. If the focal spot is to be relatively large, for example 1.5-2 mm. wide, the wire will preferably be about 0.008 inch in diameter. If a small focal spot of 0.3-1 mm., for example, is to be produced, the wire diameter will preferably be about 0.0035 inch. These examples of wire. size are only exemplary and the wire diameter may vary substantially from these examples.
  • focal spot refers to the spot or area of the target surface which is impinged by electrons from the cathode 22.
  • the length of the focal spot 62 will becontrolled primarily by the length of the filament in the cathode and somewhat by the geometry of thefocusing cup or grid (not shown) in which the filament is mounted, as is well known.
  • the width dimension B of focal spot 62 is almost entirely controlled by the grid or cup as is also well known.
  • the electrons will bombard the target in the area indicated by numeral 62 in FIG. 5
  • the resultant X-ray beam to be utilized will be directed alonga path extending from the spot 62 in a direction substantially perpendicular tothe axis of the tube. This effective X-ray beam is directed, therefore, in the general direction indicated by the dotted lines denoted C in FIG.
  • the under surface of the focal track ring 36 is provided with an annular circumferential groove 70 as shown in FIG. 4, and the adjacent surface of supporting disc on ring 38 is provided with an annular projection or ridge 72 which is aligned with the groove 70 and extends thereinto as shown.
  • the ridge 72 projects into the aligned groove 70 and in doing so it exerts considerable pressure upon the adjacent portions of the wire 60, tending to tighten it.
  • the turns of wire 60 may be slightly spaced from adjacent turns. This is the case near the outer peripheral edge of surface 46 when extremely fine wire is being employed. However, in such an event the electrons impinging upon the target in these areas will engage the small exposed surface areas of the focal track surface 46 and will generate X-radiation directly from this surface.
  • the layer of wire may be overlaid with an additional layer or layers of windings to cover the exposed surface areas of the focal track surface.
  • the convolutions provided by the wire should extend radically from the geometric center of the focal track ring 36. If the convolutions were to extend perpendicularly in the direction of the curve of the annulus, it will be apparent that some of the high portions of the convolutions will effectively intercept and block escape of some of the desirable X-radiation.
  • a stationary anode X-ray tube may be provided with this invention as illustrated in FIG. 9.
  • the stationary anode tube shown in FIG. 9 includes an envelope within one end portion of which is an anode 88.
  • Anode 88 is a body of copper, usually, which is provided with a hollow cylindrical extension portion 90 having an open end directed toward the cathode.
  • An X-ray emitting target button 92 is provided in the base of the cavity thus formed in the anode for the purpose of receiving electrons from the cathode and directing resultant X-rays out through an opening 94 and then through the wall of the envelope 68.
  • a block or body of graphite, copper, or other selected backing material 96 is deposited in the bottom of the hollow anode extension and is provided with an inclined surface having a recess therein in which the target button 92 is positioned.
  • a sleeve or shell 98 of graphite or other selected high thermal capacity material is then positioned in the extensionwith one end thereof engaging the target button 92.
  • Sleeve 98 is provided with an opening 97 which may contain a window 99 of beryllium or other material highly transmissive to X-radiation which is suitably aligned with opening 94 in extension 90 whereby X-rays emanating from the target button 92 will pass outwardly through the window 99 and opening 94.
  • the target button 92 is covered with a wire winding 100 similar to the winding in the rotating anode described hereinbefore.
  • the wires extend substantially in the direction of the angle of inclination of the button 92 so that the convolutions formed by the wires will not block escape of any of the X-radiation out through window 99.
  • a focal track surface area is increased 1r/2 that offlat surfaces whereby greater power loads can be applied to the focal track.
  • a target for X-ray tube anodes comprising a target member of material capable of X-rayemission when a surface thereof is impinged by electrons, and at least one backing member of high thermal capacity material engaging one side of the target member, said target member being an annulus extending around a perpen- 7 dicular axis, and said surface of the target member is provided with means for increasing the area thereof, said means comprising at least one layer of wires arranged in side-by-side relation, each individual wire extending substantially radially with respect to said axis.
  • vfitting means comprises an annular ridge in the adjacent abutting surface of the backing member and a comating annular groove in the target member, and further comprises means for mechanically clamping said members together to force the ridge into the groove and thereby tightening the wire therebetween.
  • An X-ray tube comprising a hermetically sealed envelope, a cathode electrode and an anode electrode located in spaced relation within the envelope, and means for connecting said electrodes to external sources of electrical energy, said anode comprising an axial support, and an X-ray generating target assembly mounted on the support, for rotation about the axis of the support said target assembly comprising a first member composed primarily of high thermal capacity material sandwiched between second and third members of high thermal capacity material, a focal track area of said first member being exposed, and means for mechanically retaining said members in intimate physical heat conductive relation, said focal track area comprising parallel corrugations, said corrugations comprising surfaces of wires disposed on said area in substantially side-by-side relation, each individual wire extending substantially radially of said axis.

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  • X-Ray Techniques (AREA)
US00168330A 1971-08-02 1971-08-02 Targets for x ray tubes Expired - Lifetime US3821581A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
US00168330A US3821581A (en) 1971-08-02 1971-08-02 Targets for x ray tubes
GB3312872A GB1359121A (en) 1971-08-02 1972-07-14 Target for x-ray tubes
CH1137572A CH567334A5 (OSRAM) 1971-08-02 1972-07-31
FR7227674A FR2148146B1 (OSRAM) 1971-08-02 1972-08-01
DE2237855A DE2237855C3 (de) 1971-08-02 1972-08-01 Röntgenröhrendrehanode
JP47076989A JPS5214079B2 (OSRAM) 1971-08-02 1972-08-02

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US00168330A US3821581A (en) 1971-08-02 1971-08-02 Targets for x ray tubes

Publications (1)

Publication Number Publication Date
US3821581A true US3821581A (en) 1974-06-28

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ID=22611074

Family Applications (1)

Application Number Title Priority Date Filing Date
US00168330A Expired - Lifetime US3821581A (en) 1971-08-02 1971-08-02 Targets for x ray tubes

Country Status (6)

Country Link
US (1) US3821581A (OSRAM)
JP (1) JPS5214079B2 (OSRAM)
CH (1) CH567334A5 (OSRAM)
DE (1) DE2237855C3 (OSRAM)
FR (1) FR2148146B1 (OSRAM)
GB (1) GB1359121A (OSRAM)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3900751A (en) * 1974-04-08 1975-08-19 Machlett Lab Inc Rotating anode x-ray tube
US3943393A (en) * 1975-02-13 1976-03-09 The Machlett Laboratories, Inc. Stress free filament structure
US3959685A (en) * 1975-02-18 1976-05-25 Konieczynski Ronald D Heat sink target
US3982148A (en) * 1975-05-07 1976-09-21 Ultramet Heat radiating coating and method of manufacture thereof
EP0091035A1 (en) * 1982-04-01 1983-10-12 General Electric Company X-ray target attachment
US4847883A (en) * 1986-01-30 1989-07-11 Le Carbone Lorraine Support for rotary target of x-ray tubes
US4958364A (en) * 1987-12-22 1990-09-18 General Electric Cgr Sa Rotating anode of composite material for X-ray tubes
US7184520B1 (en) * 2003-01-29 2007-02-27 Varian Medical Systems Technologies, Inc. Component mounting system with stress compensation
US12512289B2 (en) * 2023-09-07 2025-12-30 GE Precision Healthcare LLC X-ray tube anode with optimized area focal spot track

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR3019372A1 (fr) * 2014-03-31 2015-10-02 Acerde Anode pour l'emission de rayons x et procede de fabrication

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3900751A (en) * 1974-04-08 1975-08-19 Machlett Lab Inc Rotating anode x-ray tube
US3943393A (en) * 1975-02-13 1976-03-09 The Machlett Laboratories, Inc. Stress free filament structure
US3959685A (en) * 1975-02-18 1976-05-25 Konieczynski Ronald D Heat sink target
US3982148A (en) * 1975-05-07 1976-09-21 Ultramet Heat radiating coating and method of manufacture thereof
EP0091035A1 (en) * 1982-04-01 1983-10-12 General Electric Company X-ray target attachment
US4847883A (en) * 1986-01-30 1989-07-11 Le Carbone Lorraine Support for rotary target of x-ray tubes
US4958364A (en) * 1987-12-22 1990-09-18 General Electric Cgr Sa Rotating anode of composite material for X-ray tubes
US7184520B1 (en) * 2003-01-29 2007-02-27 Varian Medical Systems Technologies, Inc. Component mounting system with stress compensation
US12512289B2 (en) * 2023-09-07 2025-12-30 GE Precision Healthcare LLC X-ray tube anode with optimized area focal spot track

Also Published As

Publication number Publication date
DE2237855A1 (de) 1973-03-01
JPS5214079B2 (OSRAM) 1977-04-19
CH567334A5 (OSRAM) 1975-09-30
GB1359121A (en) 1974-07-10
DE2237855C3 (de) 1979-12-06
FR2148146B1 (OSRAM) 1977-07-22
DE2237855B2 (de) 1979-04-12
FR2148146A1 (OSRAM) 1973-03-11
JPS4825489A (OSRAM) 1973-04-03

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Legal Events

Date Code Title Description
AS Assignment

Owner name: VARIAN ASSOCIATES, INC., A DE CORP., STATELESS

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:MACHLETT LABORATORIES;REEL/FRAME:005060/0761

Effective date: 19890129