EP0491471A2 - Tube à rayons x de haute puissance - Google Patents

Tube à rayons x de haute puissance Download PDF

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Publication number
EP0491471A2
EP0491471A2 EP91310751A EP91310751A EP0491471A2 EP 0491471 A2 EP0491471 A2 EP 0491471A2 EP 91310751 A EP91310751 A EP 91310751A EP 91310751 A EP91310751 A EP 91310751A EP 0491471 A2 EP0491471 A2 EP 0491471A2
Authority
EP
European Patent Office
Prior art keywords
window
center section
ray generating
generating tube
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.)
Withdrawn
Application number
EP91310751A
Other languages
German (de)
English (en)
Other versions
EP0491471A3 (en
Inventor
John E. Richardson
James E. Boye
Thomas J. 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
Varian Associates 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 Varian Associates Inc filed Critical Varian Associates Inc
Priority to EP99123769A priority Critical patent/EP0991106A3/fr
Publication of EP0491471A2 publication Critical patent/EP0491471A2/fr
Publication of EP0491471A3 publication Critical patent/EP0491471A3/en
Withdrawn legal-status Critical Current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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/16—Vessels; Containers; Shields associated therewith
    • H01J35/18—Windows
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/16—Vessels; Containers; Shields associated therewith
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/12—Cooling
    • H01J2235/122—Cooling of the window
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/12—Cooling
    • H01J2235/1225—Cooling characterised by method
    • H01J2235/1262—Circulating fluids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/16—Vessels
    • H01J2235/165—Shielding arrangements
    • H01J2235/167—Shielding arrangements against thermal (heat) energy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/16—Vessels
    • H01J2235/165—Shielding arrangements
    • H01J2235/168—Shielding arrangements against charged particles

Definitions

  • the present invention relates to reducing the effects of excessive heat buildup on the x-ray transmission window and the tube envelope surfaces of a high power metal envelope x-ray generating tube.
  • a stream of electrons is emitted from a cathode and accelerated in a high voltage potential difference to strike the target area of an anode surface. Electromagnetic energy is thus produced in the form of x-rays.
  • the tube envelope surfaces are heated by several means. Heat is generated in the target from bombardment of the primay electron beam created by the cathode. This heat is radiated to the envelope of the x-ray tube. Heat is also generated in the envelope from secondary electron bombardment from electrons back scattered from the focal spot on the target. In this context, reference to "secondary" electrons includes backscattered electrons. Heating of the envelope is higher in the window area due to the contribution of electrons generated by back scattered secondary electrons. If the temperature in the area of the window rises too high, dielectric oil on the exterior of the x-ray tube will boil or break down. This is highly undesirable since the oil must maintain its electrical dielectric properties in the x-ray tube housing.
  • CT computed tomography
  • CAT computed tomography
  • thermal energy in the anode is the first limiting factor in power output, longevity, and efficiency of the x-ray generating tubes.
  • the need for continuous use, high power x-ray tubes has become even stronger with the advent of new types of medical equipment such as CAT scanners and other high power x-ray applications such as digital radiography, and angiography.
  • Radiation produced from the secondary electrons is called "off focal radiation" and is undesirable because it creates a background radiation pattern which does not contribute to the x-ray image.
  • Energy of the secondary electrons, rather than producing x-rays, is released as heat, thereby elevating the anode and envelope tube surface temperatures.
  • High power x-ray generating tubes typically include a glass center portion immersed in dielectric oil. However, it is possible to achieve higher power levels with tubes having a metal center section. The propensity to overheat in the window area of x-ray tubes is seen mainly in high power applications in metal center x-ray tubes. By reducing the power, heat buildup can be reduced. However, this resolution is not satisfactory for applications requiring high power. Alternatively, attempts have been made to reduce the effects of heat buildup.
  • U.S. Patent No. 4,819,260 and European Patent No. B1 0 059 238 address oll focal radiation.
  • U.S. Patent No. 4,819,260 is directed to a magnetically controlled electron beam which prevents migration of the focal spot of an electron stream on a rotating anode.
  • European Patent No. B1 0 059 238 discloses a metal screen which is inserted between the cathode and the anode and a voltage is applied to the screen. Neither of these systems addresses heat produced by secondary electron bombardment to cool the vacuum envelope.
  • U.S. Patent No. 4,841,557 discloses a rotating anode in which the housing is cooled by circulating, within the housing body, the outer immersion fluid in which the housing is retained. Interior conduits and connections require that a complicated structure be included for circulation of the fluid.
  • Another object of this invention is to provide an anode structure maintained at ground potential.
  • the present invention relates to a high power metal center x-ray generating tube for reducing the effects of excessive heating of the x-ray transmission window by secondary electron bombardment.
  • the present invention includes an x-ray generating tube consisting of a vacuum envelope having a metal center section, a stationary cathode and a rotating anode. A high potential is created between the rotating anode and the cathode to cause an electron beam to strike the anode with sufficient energy to generate an x-ray beam through a window formed in the tube envelope.
  • the present invention seeks to dissipate heat which can be generated in two ways. First, heat is generated in the target from bombardment of the primary electron x-ray beam created by the cathode. This heat is radiated to the envelope of the x-ray tube. Second, heat is generated in the envelope from seconday electron bombardment from electrons back scattered from the target.
  • the rotating anode is preferably held at ground potential along with the metal center section, while the cathode is at high voltage so as to maintain a potential between the cathode and anode. It is thus possible to provide a more intimate design between the cooling means and anode, using a coolant, such as water, which need not provide a dielectric standoff between the anode and cooling means. With the anode at ground, the hardware mechanism for cooling is less complicated. Alternatively, the anode can be at high positive voltage and the cathode at high negative voltage, resulting in a similar potential difference.
  • a shield intercepts back scattered secondary electrons, preventing them from striking the window, thereby avoiding secondary electron bombardment of the window.
  • the shield is disposed adjacent to the window and includes a contoured surface to match the high voltage field lines between the cathode and anode.
  • a coolant is circulated around the outer portion of the window to dissipate heat. As discussed above, because the metal center section is at ground potential, it is possible to circulate water as the selected coolant.
  • heat generation by the secondary electrons back scattered from the anode is mitigated by way of an insulating means.
  • the insulating means provides a build up of negative charge on the inner surface of the window to decelerate and repel the back scattered electrons, reducing the amount of electron energy bombarding the window and, thereby, reducing excessive heating of the window.
  • Electrons are collected on the inner surface of the window for build up of a negative charge to repel electrons from the window surface.
  • a coating of conductive material may also be formed on the window surface.
  • the window is electrically insulated from the envelope so as to form a floating potential on the surface of the window.
  • the effects of excessive heating are reduced by a double wall formed in the metal center section in the vicinity of the window.
  • a closed space is created between an inner and outer wall for circulation of a coolant to conduct heat through the inner wall and away from the window.
  • the window also includes an inner and outer window in the respective inner and outer walls.
  • a closed space can be formed such that coolant is circulated around the entire portion of the metal center section.
  • FIG. 1 is a cross sectional view of the preferred embodiment of the x-ray generating tube of the present invention.
  • FIG. 2 is a cross sectional view of a second embodiment of the x-ray generating tube of the present invention.
  • FIG. 3 is a cross sectional view of a third embodiment of the x-ray generating tube of the present invention.
  • FIG. 4 is a cross sectional view of a fourth embodiment of the x-ray generating tube of the present invention.
  • FIGS. 1-4 illustrate an x-ray generating tube 2 including a vacuum envelope 4 comprising a metal center section 6.
  • a stationary cathode 8 and a rotating anode 10 are housed within vacuum envelope 4.
  • anode 10 is held at ground potential.
  • High voltage means 12 are provided for creating a potential between cathode 8 and anode 10 to cause an electron beam generated by cathode 8 to strike anode 10 with sufficient energy to generate x-rays 14.
  • a window 16 permits transmission of x-rays 14 for high power applications.
  • Window 16 is preferably constructed of beryllium, but may be any material through which x-rays can be transmitted.
  • An enlarged region 22 of metal center section 6 surrounds window 16 such that the window slightly protrudes from the metal center section, outward of vacuum envelope 4.
  • Shield 18 is formed integrally with or affixed to the interior surface of enlarged region 22.
  • a contoured surface 24 intercepts secondary electrons 20 away from the window area.
  • Contoured surface 24 is continuous with the inner surface of center section 6, curving so as to extend toward the interior of vacuum envelope 4 and match the high voltage field lines between cathode 8 and anode 10.
  • An interior, transverse face 26 is generally flat and extends from a tip 30 of contoured surface 24 to an indentation 32 for retaining window 16 in place. Interior transverse face 26 is angled slightly from tip 30 outwardly to window 16.
  • a generally flat, exterior, transverse face 28 extends from the outer surface of center section 6 to the outer edge of enlarged region 22, approximately aligned with window 16.
  • Juxtaposed with exterior transverse face 28 is a coil 34 for circulating a forced coolant around window 16. Heat generated by secondary electrons 20 bombarding shield 18 and heat radiated from target 11 is removed by conduction through the shield and carried away by the forced coolant through coil 34. Because anode 10 is at ground potential along with metal center section 6, it is possible to use water as the selected coolant immediately adjacent to the anode. Thus, the hardware required for cooling is less complicated than would be required for a high voltage anode.
  • high voltage means 12 creates a potential between cathode 8 and anode 10 to cause an electron beam to strike the anode with sufficient energy to generate x-rays 14.
  • Heat is generated by this electron beam from secondary electrons 20.
  • Shield 18 absorbs the secondary electrons, collecting the heat along with heat generated by primary electron beam 14. The heat is conducted by coolant forced through coils 34 to ensure that window 16 remains cool.
  • FIGS. 2 and 3 are similar to FIG. 1, differing from FIG. 1 only in the circulation of the forced coolant.
  • x-ray generating tube 2 of FIGS. 2 and 3 include metal center section 6, stationary cathode 8, rotating anode 10, window 16 and shield 18.
  • a double walled closed space 36 is formed in metal center section 6. Closed space 36 is positioned between an inner wall 38 and an outer wall 40 for circulation of forced coolant. The coolant enters closed space 36 through a coolant inlet 42, circulates around vacuum envelope 4 and exits through a coolant outlet 44.
  • Window 16 of FIG. 2 is identical to window 16 of FIG. 1, i.e., slightly protruding from enlarged region 22 outwardly of vacuum envelope 4. Closed space 36 surrounds shield 18 and window 16 for conduction of heat away from the window. Heat radiated from anode 8 is conducted through inner wall 38 and convected away with the liquid coolant circulating between inner wall 38 and outer wall 40.
  • a double walled closed space 36 is also formed in metal center section 6.
  • metal center section 6 of FIG. 3 is identical to the metal center section of FIG. 1.
  • Closed space 36 is localized in the vicinity of window 16. It is positioned between the outer surface 38a of metal center section 6 and an external outer wall 40 coupled to the exterior the metal center section in the vicinity of the window along only one side of vacuum envelope 4.
  • An inner window 16a is identical to window 16 of FIG. 1.
  • an outer window 16b is formed in external outer wall 40 and spaced from window 16a for transmission of x-rays 14 through both inner window 16a and outer window 16b.
  • the coolant enters closed space 36 through a coolant inlet 42, circulates between window 16a and 16b and exits through a coolant outlet 44. Heat generated by primary electrons 14 and heat from secondary electrons 20 is conducted through inner wall 38a and convected away from the circulating cooling fluid.
  • x-ray generating tube 2 includes metal center section 6, stationary cathode 8, end-grounded rotating anode 10, high voltage means 12 and window 16.
  • FIG. 4 differs from FIG. 1 in the means for deflecting secondary electrons 20 back scattered from anode 10 away from window 16 to avoid secondary electron bombardment of envelope 4.
  • FIG. 4 includes, rather than a shield 18 as shown in FIGS. 1-3, a window 16 having a dielectric material such as ceramic or beryllium oxide material on the inner surface 16a of the window. The material selected acts as an insulator for collecting electrons on inner surface 16a of window 16.
  • a light coating of semiconductive material 46 is preferably formed on inner surface 16a, electrically insulated from vacuum envelope 4 so as to form a floating potential on inner surface 16a.
  • the preferred embodiments describe a rotating anode in a metal center tube; however, it is within the scope of this invention to cool an x-ray generating tube having a stationary anode.
  • the embodiment of FIG. 3 may be constructed with or without a shield. In the embodiment without a shield, the closed space, alone, prevents excessive heating of the window.
  • the means for preventing excessive heating may be of any form not shown or described herein.
  • a magnet may be employed outside of the envelope to deflect secondary electrons from the window.
  • a power supply may be attached to any of the described embodiments to produce a charge, thereby enhancing the force for repelling the secondary electrons.

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  • X-Ray Techniques (AREA)
EP19910310751 1990-11-21 1991-11-21 High power x-ray tube Withdrawn EP0491471A3 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP99123769A EP0991106A3 (fr) 1990-11-21 1991-11-21 Tube à rayons x de haute puissance

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US61646490A 1990-11-21 1990-11-21
US616464 1990-11-21

Related Child Applications (1)

Application Number Title Priority Date Filing Date
EP99123769A Division EP0991106A3 (fr) 1990-11-21 1991-11-21 Tube à rayons x de haute puissance

Publications (2)

Publication Number Publication Date
EP0491471A2 true EP0491471A2 (fr) 1992-06-24
EP0491471A3 EP0491471A3 (en) 1992-09-30

Family

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Family Applications (2)

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EP19910310751 Withdrawn EP0491471A3 (en) 1990-11-21 1991-11-21 High power x-ray tube
EP99123769A Withdrawn EP0991106A3 (fr) 1990-11-21 1991-11-21 Tube à rayons x de haute puissance

Family Applications After (1)

Application Number Title Priority Date Filing Date
EP99123769A Withdrawn EP0991106A3 (fr) 1990-11-21 1991-11-21 Tube à rayons x de haute puissance

Country Status (2)

Country Link
EP (2) EP0491471A3 (fr)
JP (1) JPH04315752A (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0924742A2 (fr) * 1997-12-19 1999-06-23 Picker International, Inc. Moyens pour éviter la surchauffe de la fenêtre d'un tube à rayons X
EP1475819A2 (fr) 1997-08-29 2004-11-10 Varian Medical Systems Technologies, Inc. Generateur de rayons x a boitier integre
WO2004107384A2 (fr) * 2003-05-30 2004-12-09 Koninklijke Philips Electronics N.V. Retrodiffusion amelioree d'electrons dans des tubes a rayons x
WO2006003533A1 (fr) * 2004-06-30 2006-01-12 Koninklijke Philips Electronics, N.V. Dispositif de refroidissement de tubes a rayons x
DE102008038569A1 (de) * 2008-08-20 2010-02-25 Siemens Aktiengesellschaft Röntgenröhre
US20140177796A1 (en) * 2011-06-07 2014-06-26 Canon Kabushiki Kaisha X-ray tube
US20150043718A1 (en) * 2013-08-08 2015-02-12 Ronald Dittrich Single-Pole X-Ray Emitter

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6215852B1 (en) * 1998-12-10 2001-04-10 General Electric Company Thermal energy storage and transfer assembly
US7016472B2 (en) * 2002-10-11 2006-03-21 General Electric Company X-ray tube window cooling apparatus
US6714626B1 (en) * 2002-10-11 2004-03-30 Ge Medical Systems Global Technology Company, Llc Jet cooled x-ray tube window
JP4644508B2 (ja) * 2005-03-30 2011-03-02 東芝電子管デバイス株式会社 Ｘ線管
JP4828895B2 (ja) * 2005-08-29 2011-11-30 株式会社東芝 Ｘ線管装置の電圧印加方法およびｘ線管装置
DE102005049455B4 (de) * 2005-10-15 2007-11-22 Ziehm Imaging Gmbh Wärmetauscher für einen Einkessel-Generator einer Röntgendiagnostikeinrichtung mit einer Drehanodenröhre mit Glasgehäuse
US7616736B2 (en) * 2007-09-28 2009-11-10 Varian Medical Systems, Inc. Liquid cooled window assembly in an x-ray tube
JP5225881B2 (ja) * 2008-02-08 2013-07-03 バリアン・メディカル・システムズ・インコーポレイテッド Ｘ線管およびｘ線管冷却システム
WO2009127995A1 (fr) * 2008-04-17 2009-10-22 Philips Intellectual Property & Standards Gmbh Tube à rayons x et à électrode de collecte d’ions passive
US8130910B2 (en) * 2009-08-14 2012-03-06 Varian Medical Systems, Inc. Liquid-cooled aperture body in an x-ray tube
JP2010104819A (ja) * 2010-02-01 2010-05-13 Toshiba Corp Ｘ線コンピュータ断層撮影装置及びｘ線管装置
CN106504967B (zh) * 2016-12-14 2018-01-30 云南电网有限责任公司电力科学研究院 阴阳两极具有旋转功能的x射线管

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3124710A (en) * 1960-03-17 1964-03-10 X-ray tubes
US3334256A (en) * 1964-03-20 1967-08-01 Dunlee Corp Sealed window for x-ray generator with shield for seal
EP0009946A1 (fr) * 1978-10-02 1980-04-16 Pfizer Inc. Tube à rayons X
JPS60101848A (ja) * 1983-11-09 1985-06-05 Hitachi Ltd Ｘ線管

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BE355009A (fr) * 1927-10-18
NL157981B (nl) * 1950-03-04 Lummus Co Luchtgekoelde condensorinrichting.
DE2833093A1 (de) * 1978-07-28 1980-02-07 Licentia Gmbh Roentgenroehre
JPS5818900A (ja) * 1981-07-27 1983-02-03 Hitachi Ltd Ｘ線管装置
US4731804A (en) * 1984-12-31 1988-03-15 North American Philips Corporation Window configuration of an X-ray tube

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3124710A (en) * 1960-03-17 1964-03-10 X-ray tubes
US3334256A (en) * 1964-03-20 1967-08-01 Dunlee Corp Sealed window for x-ray generator with shield for seal
EP0009946A1 (fr) * 1978-10-02 1980-04-16 Pfizer Inc. Tube à rayons X
JPS60101848A (ja) * 1983-11-09 1985-06-05 Hitachi Ltd Ｘ線管

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, vol. 9, no. 251 (E-348)[1974], 8th October 1985; & JP-A-60 101 848 (HITACHI) 05-06-1985 *

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1475819A2 (fr) 1997-08-29 2004-11-10 Varian Medical Systems Technologies, Inc. Generateur de rayons x a boitier integre
EP1475819B1 (fr) * 1997-08-29 2013-03-06 Varian Medical Systems, Inc. Générateur de rayons X à boîtier unitaire
EP0924742A2 (fr) * 1997-12-19 1999-06-23 Picker International, Inc. Moyens pour éviter la surchauffe de la fenêtre d'un tube à rayons X
EP0924742A3 (fr) * 1997-12-19 2000-01-05 Picker International, Inc. Moyens pour éviter la surchauffe de la fenêtre d'un tube à rayons X
WO2004107384A2 (fr) * 2003-05-30 2004-12-09 Koninklijke Philips Electronics N.V. Retrodiffusion amelioree d'electrons dans des tubes a rayons x
WO2004107384A3 (fr) * 2003-05-30 2005-07-07 Koninkl Philips Electronics Nv Retrodiffusion amelioree d'electrons dans des tubes a rayons x
US7260181B2 (en) 2003-05-30 2007-08-21 Koninklijke Philips Electronics, N.V. Enhanced electron backscattering in x-ray tubes
WO2006003533A1 (fr) * 2004-06-30 2006-01-12 Koninklijke Philips Electronics, N.V. Dispositif de refroidissement de tubes a rayons x
DE102008038569A1 (de) * 2008-08-20 2010-02-25 Siemens Aktiengesellschaft Röntgenröhre
US20140177796A1 (en) * 2011-06-07 2014-06-26 Canon Kabushiki Kaisha X-ray tube
US20150043718A1 (en) * 2013-08-08 2015-02-12 Ronald Dittrich Single-Pole X-Ray Emitter
US9257255B2 (en) * 2013-08-08 2016-02-09 Siemens Aktiengesellschaft Single-pole x-ray emitter

Also Published As

Publication number Publication date
JPH04315752A (ja) 1992-11-06
EP0991106A2 (fr) 2000-04-05
EP0991106A3 (fr) 2000-05-03
EP0491471A3 (en) 1992-09-30

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