EP0168736B1 - Röntgendrehanode mit Oberflächenbeschichtung - Google Patents

Röntgendrehanode mit Oberflächenbeschichtung Download PDF

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Publication number
EP0168736B1
EP0168736B1 EP85108417A EP85108417A EP0168736B1 EP 0168736 B1 EP0168736 B1 EP 0168736B1 EP 85108417 A EP85108417 A EP 85108417A EP 85108417 A EP85108417 A EP 85108417A EP 0168736 B1 EP0168736 B1 EP 0168736B1
Authority
EP
European Patent Office
Prior art keywords
coating
rotary
layer
focal track
ray anode
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
EP85108417A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0168736A2 (de
EP0168736A3 (en
Inventor
Peter Dr. Rödhammer
Hubert Dr. Bildstein
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.)
Metallwerk Plansee GmbH
Original Assignee
Metallwerk Plansee GmbH
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 Metallwerk Plansee GmbH filed Critical Metallwerk Plansee GmbH
Publication of EP0168736A2 publication Critical patent/EP0168736A2/de
Publication of EP0168736A3 publication Critical patent/EP0168736A3/de
Application granted granted Critical
Publication of EP0168736B1 publication Critical patent/EP0168736B1/de
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
    • H01J35/08—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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/58—Cooling; Heating; Diminishing heat transfer
    • F04D29/5806—Cooling the drive system

Definitions

  • the invention relates to an X-ray rotary anode with a ring-shaped focal track, consisting of a base body, with or without a separate focal track coating, made of refractory metals and / or their alloys, and of a coating of refractory compounds applied to the focal track at least on partial areas thereof.
  • heat radiation from a body occurs in accordance with the Stefan-Boltzmann radiation law and is proportional to the fourth power of the temperature, to the surface and to the hemispherical emissivity E.
  • the radiation power of x-ray rotary anodes can in principle be increased by higher operating temperatures; however, the material-related limit temperatures have already been reached in the x-ray rotary anodes manufactured according to the prior art.
  • the radiating area can be enlarged as a measure to increase the radiated power on the one hand by roughening the anode surface and on the other hand by increasing the diameter and thickness of the anode. The latter is only possible to a limited extent due to the increase in the torque and the weight of the anode.
  • the focal path area in particular makes a disproportionate contribution to radiation cooling in relation to its area share of the x-ray rotary anode (typically: 25 to 30% of the total area).
  • An increase in the emissivity E in the focal path area from, for example, 0.25 for W / re focal path coverings to 0.8 increases in theory the radiation cooling of a coated anode that can be achieved at the same limit temperatures under CT conditions up to 40%.
  • the working temperatures of the anode can be significantly reduced by a coating that includes the focal path area, with the load conditions being kept the same.
  • French Patent No. 1,371,880 describes the carbides, nitrides and borides of the transition metals as possible layer materials on rotating anodes of different substrate materials to improve the heat radiation.
  • the preferred coating material is tantalum carbide because of its high emission coefficient, but also because of its high melting point and because of its low material evaporation rates at high temperatures. A value of 25 ⁇ m is given as the minimum layer thickness. Intermediate layers of rhenium are recommended to prevent reactions between the base material and the carbide. According to the wording of the claim, the patent does indeed cover the entire rotating anode surface, including the focal track. For individual exemplary embodiments, however, it is expressly recommended that the focal path be excluded from the coating.
  • Fully coated rotating anodes of the type mentioned have the disadvantage that because of the low thermal conductivity z. B. of the patent by means of plasma spraying brought TaC (approx. 1/20 of the tungsten) with the mentioned layer thicknesses very high temperature gradients occur across the cross section of the layer. These cause high mechanical stresses in the layer and in the layer-substrate transition zone, and the high brittleness of the carbide leads to cracks or chips in the coating. The resulting roughening of the surface in the region of the focal path is felt to be particularly disadvantageous, since this significantly affects the yield of the X-rays.
  • the object of the present invention is therefore to increase the heat radiation from X-ray rotary anodes by applying a coating which encloses the focal path area and thereby avoids the disadvantages of known designs, above all the lack of thermal shock resistance and the insufficient layer adhesion.
  • the heat radiation coating has a thickness between 0.1 microns and 2 microns, the source of the X-rays mainly in the under the coating
  • the design of the x-ray rotary anode according to the present invention leads to a targeted division of the functions of thermal emission on the one hand and generation of the x-rays on the other.
  • the layer thickness within the claimed layer thickness range is determined solely according to the requirements of the emissivity and the thermo-mechanical one as well as the metallurgical long-term stability of the thermal-emissive coating.
  • the generation of the X-rays is subordinate to the above criteria - depending on the circumstances, the coating practically does not influence it or at least influences it to a certain extent.
  • the layer thicknesses for the layer materials according to the invention at 0.1 to 2 ⁇ m, are far below the known layer thicknesses including the focal path.
  • the measures according to the present invention can achieve a 20-40% increase in heat radiation depending on the design and operating mode of the X-ray rotary anode. It was not foreseeable by the average person skilled in the art that coatings on the focal path have such favorable thermo-mechanical stabilities within the claimed layer thickness range. This is the only way to explain that the coatings according to the invention have so far neither been published nor implemented in practice, although the proposal for the coating itself was made more than 20 years ago.
  • the coating consists of a carbide, nitride or a carbonitride of the transition metals Hf, Ta or W or a mixed carbide of these metals, in particular a tantalum carbide coating of the composition TaC, (0.8 ⁇ x ⁇ 1.0) or a tantalum carbonitride -Coating the composition TaC y N z (0.8 ⁇ y + z ⁇ 1).
  • the difference in the atomic numbers between the metallic component of the coating on the one hand and the main component of the focal track covering on the other hand is ⁇ 3.
  • the coating has a thickness of less than 0.5 ⁇ m.
  • a small layer thickness precludes the X-ray radiation generated from being significantly influenced by the coating.
  • the thermal emissivity of the anode is at least predominantly determined by the coating and not by the base material.
  • the coating is carried out by a PVD method (physical vapor deposition), in particular by reactive ion plating.
  • the focal track covering is first made in a single coating run on the base body from high-temperature-resistant materials and then applied the heat radiating coating.
  • Figure 1 shows an X-ray rotating anode of typical design in section. It consists of a base body made of refractory metals and / or their alloys -1-. The top of the anode has a separate focal track covering -3- and a coating -2- over the entire anode surface in a layer thickness according to the invention.
  • FIG. 2 shows in a diagram for a typical X-ray rotary anode loading cycle (81 kV, 250 mA, firing time 6.4 sec.)
  • x-ray rotary anodes for computer tomography are usually used today such that the focal spot is heated to approx. 1800 ° C. by brief electron bombardment and that a pause is then made until the anode cools down again to approx. 600 ° C.-800 ° C. is then to be heated again by electron bombardment.
  • the diagram contains three curves. The curves were determined for rotating anodes of the same type but with different surface properties.
  • Curve 1 shows the temperature profile of the focal path (90 ° before re-entry into the focal spot) of an X-ray rotary anode according to the present invention, i. H.
  • the anode consists of a base body made of a molybdenum alloy known under the abbreviation TZM.
  • the anode In the area of the focal path, the anode has a focal path covering made of a tungsten / rhenium alloy and is covered with an approximately 0.5 J.1.m thick tantalum carbide layer over the entire surface.
  • curve 2 shows the temperature profile for an anode of the same type, in which the side of the anode facing the cathode (the side having the focal track coating) is excluded from the coating.
  • the third curve shows the temperature profile for an anode, also of the same design, but without a tantalum carbide coating.
  • the fully coated X-ray anode while maintaining the maximum focal track temperature, has more than halved the cooling time from 300 to 130 seconds, ie practically more than doubling the exposure cycles.
  • the ratio of the number of cycles is still approximately 1.5 to 1.
  • thermo-mechanical and metallurgical stability of the coating according to the invention were convincingly demonstrated.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • X-Ray Techniques (AREA)
EP85108417A 1984-07-16 1985-07-06 Röntgendrehanode mit Oberflächenbeschichtung Expired EP0168736B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT2287/84 1984-07-16
AT0228784A AT381805B (de) 1984-07-16 1984-07-16 Roentgendrehanode mit oberflaechenbeschichtung

Publications (3)

Publication Number Publication Date
EP0168736A2 EP0168736A2 (de) 1986-01-22
EP0168736A3 EP0168736A3 (en) 1987-11-19
EP0168736B1 true EP0168736B1 (de) 1989-10-04

Family

ID=3531547

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85108417A Expired EP0168736B1 (de) 1984-07-16 1985-07-06 Röntgendrehanode mit Oberflächenbeschichtung

Country Status (4)

Country Link
EP (1) EP0168736B1 (ja)
JP (1) JPS6139352A (ja)
AT (1) AT381805B (ja)
DE (1) DE3573488D1 (ja)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008032995A1 (de) * 2008-07-14 2010-01-21 Siemens Aktiengesellschaft Röntgenröhre

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0787082B2 (ja) * 1987-07-24 1995-09-20 株式会社日立製作所 Ｘ線管用回転陽極ターゲット
AT699U1 (de) * 1993-07-19 1996-03-25 Gen Electric Drehanode für eine röntgenröhre
US7672433B2 (en) * 2008-05-16 2010-03-02 General Electric Company Apparatus for increasing radiative heat transfer in an x-ray tube and method of making same
CN117174557B (zh) * 2023-11-03 2024-01-09 上海超群检测科技股份有限公司 高能微焦点x射线管

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1050457B (de) * 1956-03-15 1959-02-12 Compagnie Generale De Radiologie, Paris Röntgenröhre mit vorzugsweise rotieren der hochtemperaturfester Anode
NL295542A (ja) * 1963-07-19 1900-01-01
US4227112A (en) * 1978-11-20 1980-10-07 The Machlett Laboratories, Inc. Gradated target for X-ray tubes

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008032995A1 (de) * 2008-07-14 2010-01-21 Siemens Aktiengesellschaft Röntgenröhre

Also Published As

Publication number Publication date
JPS6139352A (ja) 1986-02-25
AT381805B (de) 1986-12-10
ATA228784A (de) 1986-04-15
EP0168736A2 (de) 1986-01-22
EP0168736A3 (en) 1987-11-19
DE3573488D1 (en) 1989-11-09

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