EP0104515A2 - Anode rotative pour tube à rayons X de grande puissance et son procédé de fabrication - Google Patents

Anode rotative pour tube à rayons X de grande puissance et son procédé de fabrication Download PDF

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Publication number
EP0104515A2
EP0104515A2 EP83108830A EP83108830A EP0104515A2 EP 0104515 A2 EP0104515 A2 EP 0104515A2 EP 83108830 A EP83108830 A EP 83108830A EP 83108830 A EP83108830 A EP 83108830A EP 0104515 A2 EP0104515 A2 EP 0104515A2
Authority
EP
European Patent Office
Prior art keywords
amorphous carbon
ray
anode
braking body
layer
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.)
Withdrawn
Application number
EP83108830A
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German (de)
English (en)
Other versions
EP0104515A3 (fr
Inventor
Hans Dr. Pfister
Bernhard Dr. Hillenbrand
Alfred Dr. Müller
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 EP0104515A2 publication Critical patent/EP0104515A2/fr
Publication of EP0104515A3 publication Critical patent/EP0104515A3/fr
Withdrawn legal-status Critical Current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
    • H01J35/105—Cooling of rotating anodes, e.g. heat emitting layers or structures

Definitions

  • the invention relates to a high-performance X-ray rotary anode with a rotating, plate-shaped electron decelerating body, which contains a material of one or more components with a high characteristic value Z ⁇ max ⁇ ⁇ ⁇ s ⁇ c, where Z is the atomic number, ⁇ max the maximum permissible temperature, ⁇ is the thermal conductivity, f is the density and c is the specific heat, and which is thermally conductively connected to parts made of carbon which have a high emissivity ⁇ at the operating temperatures of the braking body.
  • the invention further relates to a method for producing such a rotating anode.
  • a corresponding high-performance x-ray anode can be found, for example, in the publication "Imaging systems for medical diagnostics", Siemens AG, Berlin-Munich, 1980, in particular pages 157 to 160, published by E. Krestel.
  • X-ray tubes generally contain a hot cathode at a negative potential and an anode at a positive potential in a vacuum vessel. Electrons emerge from the hot cathode due to thermal emission. A focusing device as part of the cathode bundles the emerging electrons to form a locally limited impact surface on the To force anode, the so-called focal spot. The electric field between the electrodes ensures sufficient acceleration of the electrons. In the focal spot of the anode, about 99% of the electron energy is converted into heat by the impacting electrons, while only about 1% leads to the desired X-ray radiation. The heat energy generated in the anode must be dissipated by suitable cooling.
  • the high short-term performance of X-ray tubes required for medical diagnostics * with the required exposure times and small burn spots can practically only be achieved with rotating anodes.
  • rotating the anode material that has not yet been bombarded by electron beams, that is to say that has not been heated or has largely cooled again, is brought into the electron beam.
  • the maximum short-term power of such an anode is mainly determined by the melting point, by the roughening due to the very high temperature gradients and / or the evaporation rate of the anode material in the focal spot.
  • Tungsten is considered to be a particularly suitable anode material. This is due to the high atomic number of this material, its high melting temperature and its good thermal properties compared to other high-melting materials. Accordingly, the value of the size Z ⁇ max ⁇ ⁇ s ⁇ c, which is regarded as characteristic for rotating anodes, is particularly high for this material and is approximately 370,000 (cf. the publication mentioned, pages 76 and 77).
  • Z is the atomic number
  • ⁇ max the maximum permissible temperature
  • ⁇ the heat conductivity s the density and c the specific heat.
  • the permitted maximum focal spot temperature is 20 to 30% below the melting point temperature of the anode material.
  • Radiation cooling is generally used to cool high-performance rotating anodes made of tungsten or tungsten alloys.
  • the anode assumes an average temperature of approximately 1000 ° C. on its surface facing the radiation.
  • the emitted power can thus be influenced via the emissivity (T).
  • T emissivity
  • the ⁇ values at temperatures of 1000 ° C are around 0.2.
  • the values at these temperatures are between 0.5 and 0.9.
  • the relatively low emissivity of the originally pure metal plates of the rotating anodes was attempted by blackening the back of the anode, i.e. on the side facing away from the electron radiation.
  • metal-graphite composite rotating anodes are known, the anode plates of which have a welded-on graphite disc on the back. This not only exploits the good emissivity of the graphite, but also the high specific heat of the material. In this way, high continuous outputs, e.g. at 100 mm anode diameter up to 4 kW can be emitted without the anode being heated to an unacceptably high level.
  • the graphite material is not in direct connection with the front of the anode plate which is exposed to the electrons, where the high temperatures occur. Rather, since the graphite material attached to the rear of the anode plate is separated from the high-temperature areas by the considerable thickness of the anode plate due to mechanical reasons, only a correspondingly low radiation line is achieved due to the lower temperatures prevailing there.
  • the known graphite material can also not be easily applied to the front of the anode plate, since otherwise the graphite would react with the anode material with undesired carbide formation at the temperatures prevailing there. The radiation cooling of the known rotary anode is accordingly limited.
  • the object of the present invention is to further increase the radiation cooling of this known composite rotating anode.
  • This object is achieved according to the invention for the high-performance rotating anode of the type mentioned at the outset in that at least the front of the plate-shaped braking body exposed to the electrons is at least partially provided with a layer of an amorphous carbon which has a high emissivity f at the operating temperatures of the braking body occurring there of at least 0.5 and is at least largely chemically resistant to the X-ray active material of the braking body.
  • a carbon layer which is resistant to the material of the braking body is to be understood as a layer which at most undergoes a negligible chemical reaction, in particular carbide formation, with the material of the braking body or its X-ray-active parts within the required service life of the rotating anode.
  • the advantages associated with the design of the rotating anode according to the invention can be seen in particular in that the arrangement of areas with high emissivity in the immediate vicinity of the annular focal spot zone can significantly increase the radiated power of the surface of the anode plate compared to the known embodiment of the rotating anode. This allows the temperature of the anode plate to be reduced, which leads to an increase in the life of the X-ray tube. Or you can further increase the performance of the tube without undue overheating of the anode.
  • An advantageous method for producing the high-performance x-ray rotary anode according to the invention is characterized in that the amorphous carbon layer is deposited by means of a gas discharge from hydrocarbons.
  • the rotating anode contains an anode plate 2, which serves as a braking body for electron beams generated by a hot cathode (not shown in the figure) and focused in a focusing device.
  • This anode plate is attached to a central shaft 3, which are connected to rotatable parts of a rotor not shown in the figure.
  • the rotational speeds of the rotor are generally between 16 2/3 and 300 Hz.
  • the anode plate 2 essentially comprises a base body 4, which has at least one radially outer annular portion 5, which is opposed to a central portion 6 to which the shaft 3 is fixed, is angled by a predetermined angle ⁇ .
  • This angled area 5 meets at least in an annular partial area 7 the electron beam 8 indicated by arrowed lines in the figure.
  • This partial area thus represents the focal spot zone of the anode plate 2.
  • At least this annular focal spot zone 7 of the angled area 5 is provided with an X-ray active cover layer 9. Mistake.
  • This cover layer with a thickness D of, for example, 1 to 2 mm advantageously consists of pure tungsten or a tungsten alloy such as, for example, tungsten-rhenium, while the base body 4 and the shaft For example, are made of a molybdenum alloy. If appropriate, the entire anode plate 2 can also be made of tungsten or a tungsten alloy.
  • a thin layer of an amorphous diamond-like or graphite-like carbon is applied to the anode plate 2 on the surface of its front side facing the electron beam 8.
  • the focal spot zone 7 is not coated with this carbon. If necessary, however, a corresponding coating of this zone can also be provided.
  • deposition of amorphous carbon can either be avoided by a mask technique; or one removes the amorphous carbon from this area mechanically, physically or chemically after the deposition process.
  • the focal spot zone 7 lies between an annular carbon layer 11 on the outer edge and a circular disk-shaped carbon layer 12 covering the center of the anode plate 2.
  • the carbon material of the layers has a high emissivity ⁇ , which corresponds approximately to that of a black body. ⁇ is thus at least 0.5, for example approximately 0.8, at the temperatures which arise when the electron beam 8 impacts the focal spot zone 7 in the subareas of the anode plate 2 which are immediately below the layers 11 and 12.
  • the appropriate temperatures can be there for example about 1000 v C.
  • the amorphous carbon is sufficiently chemically resistant to the material of the anode plate 2, in particular to the tungsten or the tungsten alloy of the X-ray active cover layer 9. Material practically does not react with the neighboring material of the anode plate at these temperatures during the life of the anode.
  • corresponding layers 13 or 14 made of the amorphous carbon material can also be applied to the back of the anode plate 2 facing away from the electron radiation 8 and, if appropriate, to the outer edge of the plate, in order to further increase the radiation cooling.
  • the entire, coated anode plate 2 can be provided in a known manner with radial slots in its annular, angled region 5 (cf. the publication mentioned, pages 159 and 162).
  • amorphous carbon layers on substrates is known per se (cf., for example, "Appl. Phys. Lett.” 36 (4), February 15, 1980, pages 291 and 292; "Thin Solid Films” Vol. 80 (1981) , Pages 193 to 200 and pages 227 to 234 and Vol. 60 (1979), pages 213 to 225).
  • Such layers can then be applied, for example, in a direct voltage or high-frequency plasma made of hydrocarbons or by high-frequency sputtering.
  • These layers, often called diamond similarly designated and characterized by a high hardness, should previously be used according to the publications mentioned in optical devices as anti-reflective layers of semiconductors in the infrared range or as layers for surface hardening.
  • amorphous carbon films at high temperatures of, for example, about 10 00 d C compared to the intended in general for high-performance X-ray rotary anode X-ray active materials, in particular to tungsten or tungsten alloys are sufficiently chemically resistant.
  • Corresponding amorphous carbon layers can therefore advantageously also serve to improve the radiation cooling of X-ray rotary anodes.
  • Amorphous carbon layers suitable for this can be applied to the anode plate of a rotating anode using the known methods. It is particularly advantageous to deposit the carbon layers on the anode plate by means of a gas discharge of hydrocarbons.
  • the anode plate made of pure tungsten to be coated with the amorphous carbon was first subjected to a cleaning treatment as the X-ray active material.
  • a cleaning treatment as the X-ray active material.
  • This may be achieved in particular a sand-blasting treatment with A1203 powder of about 10 / to provide diameter of the powder particles.
  • a known cathode ray etching which is also referred to as sputter etching, is possible.
  • Such sputter cleaning was carried out after the sandblasting treatment.
  • the coating chamber with the pretreated tungsten anode plate was then flowed through by methane gas or butane gas.
  • the pressure of this hydrocarbon atmosphere was about 0.1 mbar.
  • a direct current gas discharge was ignited between the tungsten anode plate connected as cathode and an anode at room temperature.
  • a glow discharge with a current density based on the cathode of about 50 to 100 / ⁇ m / cm 2 at a power density of 0.3 to 3, for example about 1 W per mbar and cm cathode area.
  • a glow discharge treatment there was a firmly adhering amorphous carbon layer with a thickness in the / um range on the anode plate.
  • This layer which has a dark gray appearance, is resistant to the tungsten of the anode plate up to temperatures of over 1000 ° C. and has a high emissivity S of about 0.8 at these temperatures.
  • the anode plate with the layers of amorphous carbon deposited on it can be subjected to a thermal aftertreatment, in particular at elevated temperatures of above 300 ° C., preferably above 500 ° C., for example. undergo at about 1000 ° C. In this way, any hydrogen that may still be incorporated in the amorphous carbon layers can be expelled from these layers.
  • the deposited carbon can also be removed again in the area of the focal spot zone, unless a masking technique precludes the deposition of the carbon during the gas discharge treatment. If necessary, however, the amorphous carbon can also be left in the focal spot zone.

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  • X-Ray Techniques (AREA)
EP83108830A 1982-09-29 1983-09-07 Anode rotative pour tube à rayons X de grande puissance et son procédé de fabrication Withdrawn EP0104515A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3236104 1982-09-29
DE19823236104 DE3236104A1 (de) 1982-09-29 1982-09-29 Hochleistungs-roentgendrehanode und verfahren zu ihrer herstellung

Publications (2)

Publication Number Publication Date
EP0104515A2 true EP0104515A2 (fr) 1984-04-04
EP0104515A3 EP0104515A3 (fr) 1986-01-15

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP83108830A Withdrawn EP0104515A3 (fr) 1982-09-29 1983-09-07 Anode rotative pour tube à rayons X de grande puissance et son procédé de fabrication

Country Status (3)

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EP (1) EP0104515A3 (fr)
JP (1) JPS5981847A (fr)
DE (1) DE3236104A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1580787A2 (fr) * 2004-03-26 2005-09-28 Shimadzu Corporation dispositif generateur des rayons X
CN111415852A (zh) * 2020-05-06 2020-07-14 上海联影医疗科技有限公司 X射线管的阳极组件、x射线管及医疗成像设备

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT391223B (de) * 1987-08-03 1990-09-10 Plansee Metallwerk Verfahren zur herstellung einer drehanode fuer roentgenroehren
DE102004003370B4 (de) * 2004-01-22 2015-04-02 Siemens Aktiengesellschaft Hochleistungsanodenteller für eine direkt gekühlte Drehkolbenröhre

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2146918A1 (de) * 1971-09-20 1973-03-22 Siemens Ag Roentgenroehren-drehanode
GB2084124A (en) * 1980-09-15 1982-04-07 Gen Electric Improved graphite X-ray tube target
US4335327A (en) * 1978-12-04 1982-06-15 The Machlett Laboratories, Incorporated X-Ray tube target having pyrolytic amorphous carbon coating

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2146918A1 (de) * 1971-09-20 1973-03-22 Siemens Ag Roentgenroehren-drehanode
US4335327A (en) * 1978-12-04 1982-06-15 The Machlett Laboratories, Incorporated X-Ray tube target having pyrolytic amorphous carbon coating
GB2084124A (en) * 1980-09-15 1982-04-07 Gen Electric Improved graphite X-ray tube target

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1580787A2 (fr) * 2004-03-26 2005-09-28 Shimadzu Corporation dispositif generateur des rayons X
EP1580787A3 (fr) * 2004-03-26 2010-11-24 Shimadzu Corporation dispositif generateur des rayons X
CN111415852A (zh) * 2020-05-06 2020-07-14 上海联影医疗科技有限公司 X射线管的阳极组件、x射线管及医疗成像设备
CN111415852B (zh) * 2020-05-06 2024-02-09 上海联影医疗科技股份有限公司 X射线管的阳极组件、x射线管及医疗成像设备

Also Published As

Publication number Publication date
EP0104515A3 (fr) 1986-01-15
DE3236104A1 (de) 1984-03-29
JPS5981847A (ja) 1984-05-11

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Inventor name: MUELLER, ALFRED, DR.