US3737699A - X-ray tube having anode target layer of molybdenum rhenium alloy - Google Patents

X-ray tube having anode target layer of molybdenum rhenium alloy Download PDF

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Publication number
US3737699A
US3737699A US00254502A US3737699DA US3737699A US 3737699 A US3737699 A US 3737699A US 00254502 A US00254502 A US 00254502A US 3737699D A US3737699D A US 3737699DA US 3737699 A US3737699 A US 3737699A
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anode
molybdenum
ray tube
rhenium
accordance
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Expired - Lifetime
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US00254502A
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English (en)
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R Gager
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Philips Nuclear Medicine Inc
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Picker Corp
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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

  • ABSTRACT An x-ray tube is described which includes a rotary anode having a target layer of molybdenum rhenium alloy provided on a base member of molybdenum.
  • the x-ray tube has a greatly increased useful life due to a lower reduction in x-ray radiation after multiple exposures at high thermal loading of the target.
  • the subject matter of the presentinvention relates generally to x-ray tubes and in particular to x-ray tubes employing rotary anodes for generating x-rays having wave length characteristics desirable in the examination of soft tissue, such as in womens breasts. Molybdenum is currently favored for such anodes but tends to crack and roughen which results in reduction of the x-ray radiation. I have found that an alloy of molybdenum and rhenium reduces this problem substantially.
  • Previous x-ray tubes such as that of U.S. Pat. No. 3,328,626 of Natter et al., granted June 27, 1967, have employed rotating anodes including base members of molybdenum which may also contain rhenium.
  • the x-ray emitting target portion of such anode is made of tungsten which is subject to x-ray radiation dropoff due to cracking and roughening of the target.
  • Other prior x-ray tubes such as that of U.S. Pat. No. 2,863,083 of Schram have employed rhenium in a thin layer over the target and the rest of the anode in order to increase the cooling speed of such anode because of the greater thermal emissivity of rhenium.
  • the rhenium layer shields the target layer from most of the electrons and emits x-rays of a different wavelength than the target layer which results in poor contrast of the x-ray images recorded on film or viewed on a fluorescent screen.
  • the anode target should be made of a molybdenum rhenium alloy containing approximately 2 to 15 percent by weight rhenium and the balance molybdenum.
  • This target may be a layer of molybdenum rhenium alloy on an anode base member of molybdenum, such target layer having a thickness on the order of about 0.04 inch.
  • An x-ray tube containing a rotary anode employing such a target layer of percent rhenium and 90 percent molybdenum was tested using 4,000 exposures each of 4 seconds duration at 60 kilovolts and 250 milliamperes.
  • X-ray radiation density measurements showed a radiation dropoff of only 10 to percent for this tube compared with a radiation dropoff several times greater than this in the case of pure molybdenum targets under similar conditions.
  • Another object of the invention is to provide such an x-ray tube having an anode which may be subjected to high thermal loading by electron bombardment during repeated exposures without greatly reducing the x-ray radiation level.
  • a further object of the present invention is to provide such an x-ray tube in which at least the target portion of its anode is made of a molybdenum rhenium alloy.
  • Still another object of the invention is to provide such an x-ray tube in which the target portion is a layer on an anode base member of molybdenum.
  • An additional object of the invention is to provide such an x-ray tube having an x-ray wavelength spectrum which is substantially the same as that of pure molybdenum.
  • FIG. 1 is a plan view of an x-ray tube made in accordance with the present invention with a portion of the envelope broken away for purposes of clarity;
  • FIG. 2 is a section view taken along the line 2-2 of FIG. 1 showing the top side of the anode of the x-ray tube;
  • FIG. 3 is a vertical section view taken along the line 33 of FIG. 2.
  • an x-ray tube in accordance with the present invention includes a cathode 10 and an anode 12 mounted within an evacuated glass envelope 14.
  • the anode may be a rotary anode which is mounted for rotation within a suitable bearing sleeve 16 in a conventional manner.
  • the cathode 10 is a thermionic cathode such as a heated filament of tungsten or thoriated tungsten which is mounted within a cathode cup type of focusing electrode 18.
  • the target portion 20 may be a frustroconical track which is rotated in the direction of arrow 21 past the electron beam.
  • the electrons are focused to strike the target portion 20 at a focal spot 22 from which x-rays are emitted through the glass envelope 14.
  • the rotating anode 12 includes an anode body member 24 of a refractory metal, such as molybdenum, and a target layer 26 of molybdenum rhenium alloy coated on at least the target portion 20 of the anode.
  • the x-ray anode 12 is fixedly mounted on a support rod 28 in any suitable manner. It has been found that the molybdenum rhenium alloy should contain between about 2% and 15% by weight rhenium, with the balance molybdenum.
  • the target layer should be relatively thick and may have a thickness between about .03 and .08 inch.
  • the molybdenum rhenium target layer greatly increasesthe useful life of the x-ray tube by reducing the radiation dropoff that occurs after numerous exposures at high thermal loading. This improvement is apparently due to the fact that the addition of rhenium reduces recrystalization and grain growth which tends to cause surface cracking. Such cracking and other surface damage reduces x-ray radiation due to self absorption of the x-rays within the target.
  • the anode may be manufactured by compacting molybdenum powder in a suitable dye cavity, followed by sintering and forging of the sintered metal body to give it the desired final shape and high density in a similar manner to that shown in U.S. Pat. No. 3,136,907 of Kieffer et al granted June 9, 1962.
  • the target layer 26 is formed by a mixture of molybdenum powder and rhenium powder, or rhenium coated molybdenum particles, provided as a layer within the dye cavity prior to compacting and sintering.
  • the entire anode may be made of rhenium molybdenum alloy but this is not very practical for economic reasons.
  • an x-ray tube having a rotary anode base of molybdenum and a target portion of an alloy of 10 percent rhenium and percent molybdenum was tested with 4,000 exposures at 60 kilovolts and 250 milliamperes while rotating at 60 revolutions per second, each exposure cycle having an exposure time of 4 seconds and a cooling time of 86 seconds between exposures.
  • the x-ray radiation density at the end of 4,000 exposures showed a reduction of only to percent from the initial radiation level compared with a radiation dropoff several times greater than this for pure molybdenum targets under similar conditions.
  • An x-ray tube in which the improvement comprises:
  • anode mounted'within said envelope and having a target portion which emits x-rays when bombarded by electrons from said cathode, said target portion consisting of a molybdenum rhenium alloy.
  • An x-ray tube in accordance with claim 1 in which said alloy contains between 2 and 15 percent rhenium.
  • An x-ray anode in which the improvement comprises:
  • an anode member having a target portion which emits x-rays when bombarded by electrons, said target portion being made of a molybdenum rhenium alloy.

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  • X-Ray Techniques (AREA)
US00254502A 1972-05-18 1972-05-18 X-ray tube having anode target layer of molybdenum rhenium alloy Expired - Lifetime US3737699A (en)

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US25450272A 1972-05-18 1972-05-18

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US (1) US3737699A (enrdf_load_stackoverflow)
JP (1) JPS4950883A (enrdf_load_stackoverflow)
CA (1) CA967218A (enrdf_load_stackoverflow)
DE (1) DE2304947A1 (enrdf_load_stackoverflow)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3836808A (en) * 1972-06-28 1974-09-17 Siemens Ag Rotary anode for an x-ray tube
US3869635A (en) * 1972-06-28 1975-03-04 Siemens Ag Rotary anode for an x-ray tube
US3894239A (en) * 1973-09-04 1975-07-08 Raytheon Co Monochromatic x-ray generator
FR2350685A1 (fr) * 1976-05-03 1977-12-02 Gen Electric Anode perfectionnee pour tube a rayons x et son procede de fabrication
US4168449A (en) * 1976-10-29 1979-09-18 Tokyo Shibaura Electric Co., Ltd. Rotary anode for X-ray tube and a method for manufacturing the same
US4731805A (en) * 1984-06-08 1988-03-15 Boyarina Maiya F Rotary anode for an x-ray tube and an x-ray tube having such anode
US4800581A (en) * 1986-10-27 1989-01-24 Kabushiki Kaisha Toshiba X-ray tube
US11043352B1 (en) * 2019-12-20 2021-06-22 Varex Imaging Corporation Aligned grain structure targets, systems, and methods of forming
US11817287B1 (en) 2022-05-13 2023-11-14 Beijing Institute Of Technology Rotary-transmission-target microfocus X-ray source and ray generation method

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3397338A (en) * 1964-02-26 1968-08-13 Siemens Ag Rotary anode plate for X-ray tubes

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3397338A (en) * 1964-02-26 1968-08-13 Siemens Ag Rotary anode plate for X-ray tubes

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3836808A (en) * 1972-06-28 1974-09-17 Siemens Ag Rotary anode for an x-ray tube
US3869635A (en) * 1972-06-28 1975-03-04 Siemens Ag Rotary anode for an x-ray tube
US3894239A (en) * 1973-09-04 1975-07-08 Raytheon Co Monochromatic x-ray generator
FR2350685A1 (fr) * 1976-05-03 1977-12-02 Gen Electric Anode perfectionnee pour tube a rayons x et son procede de fabrication
US4168449A (en) * 1976-10-29 1979-09-18 Tokyo Shibaura Electric Co., Ltd. Rotary anode for X-ray tube and a method for manufacturing the same
US4731805A (en) * 1984-06-08 1988-03-15 Boyarina Maiya F Rotary anode for an x-ray tube and an x-ray tube having such anode
US4800581A (en) * 1986-10-27 1989-01-24 Kabushiki Kaisha Toshiba X-ray tube
US11043352B1 (en) * 2019-12-20 2021-06-22 Varex Imaging Corporation Aligned grain structure targets, systems, and methods of forming
US20210193426A1 (en) * 2019-12-20 2021-06-24 Varex Imaging Corporation Aligned grain structure targets, systems, and methods of forming
US11817287B1 (en) 2022-05-13 2023-11-14 Beijing Institute Of Technology Rotary-transmission-target microfocus X-ray source and ray generation method

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Publication number Publication date
DE2304947A1 (de) 1973-12-06
JPS4950883A (enrdf_load_stackoverflow) 1974-05-17
CA967218A (en) 1975-05-06

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