EP0768699A1 - Röntgenröhre und Barrierevorrichtung dafür - Google Patents

Röntgenröhre und Barrierevorrichtung dafür Download PDF

Info

Publication number
EP0768699A1
EP0768699A1 EP96307066A EP96307066A EP0768699A1 EP 0768699 A1 EP0768699 A1 EP 0768699A1 EP 96307066 A EP96307066 A EP 96307066A EP 96307066 A EP96307066 A EP 96307066A EP 0768699 A1 EP0768699 A1 EP 0768699A1
Authority
EP
European Patent Office
Prior art keywords
ray
ray tube
anode
window
wall section
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.)
Granted
Application number
EP96307066A
Other languages
English (en)
French (fr)
Other versions
EP0768699B1 (de
Inventor
Richard Stark Enck
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.)
Kevex X Ray Inc
Original Assignee
Kevex X Ray 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 Kevex X Ray Inc filed Critical Kevex X Ray Inc
Publication of EP0768699A1 publication Critical patent/EP0768699A1/de
Application granted granted Critical
Publication of EP0768699B1 publication Critical patent/EP0768699B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • H01J2235/16—Vessels
    • H01J2235/165—Shielding arrangements
    • H01J2235/168—Shielding arrangements against charged particles

Definitions

  • the present invention relates to an X-ray tube and more specifically to an X-ray tube capable of generating high intensity X-rays without loss of reliability.
  • X-ray tubes normally include an electron gun and an anode.
  • a beam of electrons generated by the electron gun is focused to a focal spot on the anode and X-rays are generated by the interaction of the beam of electrons with the atoms of the anode.
  • These X-rays are generated in all directions from the anode in the region surrounding the focal spot.
  • the anode is substantially surrounded by an evacuated housing in which a window is formed to allow some of the X-rays to pass out of the housing, the window typically comprising a thin foil of a low atomic number metal, such as beryllium or aluminium, having a high transmission coefficient for X-radiation.
  • X-ray tubes have a number of applications which involve the treatment or analysis of a sample, for example: industrial imaging, analytical instruments and medical imaging. For such applications it is often desirable to have an X-ray tube which has a long service life, which is capable of forming a small focal spot and which is also capable of generating a high intensity of X-radiation at the sample.
  • the beam current is an effective method of increasing the power output of an X-ray tube and can also increase the intensity of X-rays at the sample.
  • the majority of electrons are either scattered by the anode or lose their energy to heat in the anode. This generation of heat within the anode can cause the anode to melt, preventing the further use of the X-ray tube without repair.
  • the anode material should be chosen to have a high melting point and a high thermal conductivity.
  • the anode may be made of a metal of high atomic number.
  • the anode is commonly comprised of copper (which has a high thermal conductivity) coated with a layer of tungsten (which has a high atomic number and a high melting point).
  • Enlarging the focal spot say by reducing the angle ⁇ at which the electrons are incident upon the anode, can increase the maximum beam current by enhancing heat dissipation.
  • increasing the size of the focal spot can adversely affect the resolution achievable for imaging applications, and decreasing ⁇ can result in an increase in the generation of scattered electrons. The problems of scattered electrons and resolution are both discussed below.
  • anode may be kept cool by rotating it so that the position of the focal spot on the anode is continually changed as the anode rotates.
  • Such rotating anodes have a greater ability to dissipate heat energy than fixed anodes.
  • anodes are usually cooled by passing a fluid, such as water or oil, through the anode to transport the heat away from the anode.
  • a second method of increasing the intensity of the X-rays at the sample is to decrease distance from the focal spot to the window (the exit distance). This is because a small exit distance allows the sample to be positioned closer to the focal spot. Optimising the exit distance, and hence the proximity of the sample to the focal spot, can also improve magnification for the imaging applications mentioned above.
  • decreasing the exit distance can also increase the number of scattered electrons which are incident upon the window, thus causing heating of the window.
  • decreasing the exit distance exacerbates the effect on the window of heat radiated from the anode. Heating of the window can be a significant source of poor reliability, particularly if the window is comprised of beryllium. Beryllium has a low heat capacity and has a low thermal conductivity so that significant temperature gradients can be formed across a beryllium window which may cause the window to rupture.
  • the exit distance must be large so that the path of the electrons is sufficiently deflected to prevent damage to the window. If a strong electric or magnetic field is used then the exit distance must also be large to prevent interference with the beam of electrons which are incident upon the anode.
  • the use of magnets or biased electrodes also occupies space between the anode and the window, preventing the exit distance from being reduced. Furthermore the use of an electrode to which a potential is applied will require the provision of insulators and feedthroughs, thus increasing complexity.
  • X-rays generated by the electron beam are emitted from the anode in all directions, but usually only X-rays having a limited range of take-off angles ⁇ (the angle between an X-ray and the surface of the anode) are used to illuminate the sample under test.
  • the selection of values of ⁇ for X-rays used in the treatment or analysis of an object can be as important as the choice of ⁇ .
  • the use of X-rays having small values of ⁇ can improve resolution for imaging applications, and can also reduce the formation of undesirable penumbra for X-ray lithographic applications.
  • X-rays emitted at small values of ⁇ can have a higher intensity than those emitted at large values of ⁇ though this effect can be offset by absorption in the anode.
  • the parameters of an X-ray tube are interrelated and optimising one parameter may lead to the worsening of another.
  • the use of X-rays having small take-off angles ⁇ can improve resolution, but can also lead to a loss of intensity due to absorption by the anode.
  • the use of small ⁇ is advantageous in some ways, but can lead to rapid degradation of the window.
  • attempts to optimise ⁇ such as those suggested in US 5206895, may lead to an increase in the exit distance and hence to loss of intensity.
  • an X-ray tube comprising:
  • said barrier means further includes at least one X-ray impermeable wall section, at least one exit aperture being formed in said X-ray impermeable wall section or sections, the or each said exit aperture being closed by said X-ray permeable wall section or sections.
  • the or each said X-ray permeable wall section is made from a material having a high melting point and a high transmission coefficient for X-rays.
  • said material also has a high thermal conductivity.
  • the said material is diamond.
  • the dimensions and position of the or each said exit aperture are such that only X-rays having take-off angles substantially in the range 0° to 30° relative to the anode surface are able to pass through the or each said exit aperture. Further preferably the dimensions and position of the or each said exit aperture are such that only X-rays having take-off angles substantially in the range 0° to 20° relative to the anode surface are able to pass through the or each said exit aperture.
  • the or each said X-ray impermeable wall section comprises a material having a high thermal conductivity.
  • the or each said X-ray impermeable wall section comprises a material having a high electrical conductivity and/or a high thermal conductivity.
  • the or each said X-ray impermeable wall section is formed of copper.
  • the incident angle ⁇ is substantially between 5° and 15°. Further advantageously, the incident angle ⁇ is substantially between 7° and 13°.
  • the largest dimension of the focal spot is substantially between 1 ⁇ m and 100 ⁇ m. Further preferably said largest dimension is between 1 ⁇ m and 25 ⁇ m.
  • the window comprises a thin sheet of beryllium foil.
  • the distance from the focal spot to the window is in the range 2 to 8 mm.
  • the invention provides a barrier means for preventing scattered electrons from reaching a window of an X-ray tube, comprising:
  • Figure 1 illustrates an X-ray tube generally indicated by 7 comprising an anode 8 and a means for generating a beam of electrons, said means comprising an electron gun 1 which is of standard design.
  • the electron gun 1 and the anode 8 are both disposed inside an evacuated housing comprising an end plate 14, a ceramic tube 2, a first weld flange 17, a second weld flange 4, an anode tube 11 and a window assembly 10.
  • the pressure within the evacuated housing is less than 10 -6 torr.
  • the electron gun 1 is provided with electrical connectors 5 for the supply of power to the electron gun 1.
  • the electron gun 1 protrudes from and is hermetically sealed to the end plate 14.
  • the end plate 14 is welded to the first weld flange 17 which is in turn brazed to the ceramic tube 2.
  • the ceramic tube 2 is brazed to the second weld flange 4.
  • the ceramic tube 2 insulates the first weld flange 17 from the second weld flange 4, so that the second weld flange 4 can be maintained at ground potential and the first weld flange 17 can be maintained at -50 kV.
  • a stainless steel tube 3 is welded to the second weld flange 4 so that the stainless steel tube 3 is at ground potential.
  • anode tube 11 One end of the anode tube 11 is formed into a flange 32 which is welded to and is in electrical contact with the second weld flange 4.
  • Anode 8 is brazed to and in electrical contact with the inside of the anode tube 11, so that both the anode tube 11 and anode 8 are at ground potential.
  • the anode 8 is comprised of copper and the anode tube 11 is comprised of stainless steel.
  • the anode 8 is cooled by passing water through a cavity 16 (shown in figure 2 only) formed in the anode tube 11. The water passes into the cavity 16 through an inlet tube 19 which is welded to the anode tube 11. Baffles (not shown) within the cavity 16 restrict the flow of the water so that the water is forced into contact with the anode 8. After flowing against the anode 8 the water passes out of the anode tube 11 through an outlet tube 13 which is welded to the anode tube 11.
  • a beam of electrons 6, which is generated by the electron gun 1, has a potential of -50 kV relative to ground on exiting the electron gun 1.
  • the beam current can have a range of values: from a few microamps up to ten milliamps.
  • the beam of electrons 6 is accelerated towards the second weld flange 4 by the potential difference between the weld flange 4 and the electron gun 1, and passes through the entrance aperture 18.
  • the beam of electrons 6 is deflected by a magnetic deflection coil 12 so that it impinges upon the anode 8 an incident angle ⁇ (shown in figure 2) of approximately 10°.
  • the beam of electrons 6 forms a focal spot 24 on the anode 8.
  • the anode 8 is coated with a layer of tungsten (not shown) in the area surrounding the focal spot 24 to form a suitable surface from which X-rays 9 may be generated.
  • the X-rays 9 are generated in all directions from the anode 8 in the region surrounding the focal spot 24.
  • the beam of electrons 6 has diameter of approximately 5 ⁇ m, but the small incident angle ⁇ results in the largest dimension of the focal spot 24 being approximately 25 ⁇ m.
  • the focal spot 24 has a larger area than would be the case for a large incident angle and thus the heat generated per unit area is reduced.
  • Those X-rays 9 which have appropriate take-off angles pass through the window assembly 10 shown in more detail in figure 2.
  • Figure 2 shows a more detailed representation of the X-ray tube 7 in the region which surrounds the anode 8.
  • An opaque wall portion comprising a copper plate 15, is brazed to and is in electric contact with the anode 8.
  • An exit aperture 34 which is formed in the copper plate 15, is closed by an X-ray permeable wall portion comprising a diamond sheet 20.
  • the diamond sheet 20 is held in place by a retaining ring 21.
  • X-rays 9, which have appropriate take-off angles, pass through the diamond sheet 20 before being transmitted to the exterior of the X-ray tube 7 by a window 31.
  • the spacing between the diamond sheet 20 and the window 31 is approximately 1.5 mm and the spacing between the diamond sheet 20 and the focal spot 24 is approximately 1.5 mm.
  • the window 31 comprises a sheet of beryllium which is brazed to both an upper ring 25 and a lower ring 26, the lower ring 26 having a ring flange 33.
  • the ring flange 33 is welded to a tube flange 28 which is formed from a short section of metal tube 29.
  • the window 31 is mounted on the anode tube 11, which includes an outer tube 23 and an inner tube 22, by inserting the metal tube 29 inside the outer tube 23.
  • a vacuum tight seal is achieved by welding the tube flange 28 to a flange 27 formed from the outer tube 23.
  • the metal tube 29, inner tube 22 and the outer tube 23 are all comprised of stainless steel.
  • the upper ring 25 and lower ring 26 are comprised of Monel (a nickel alloy).
  • Figure 2 shows the incident angle ⁇ at which the electron beam 6 is incident upon the anode 8 and also shows a take-off angle ⁇ at which one of the X-rays 9 is emitted from the anode 8.
  • Those X-rays 9 which are emitted by the X-ray tube 7 have values of ⁇ limited by the position and dimensions of the aperture 34 to the approximate range 0° to 20°.
  • the position and dimensions of the aperture 34 enables the use of the X-ray tube 7 for imaging applications in which a high resolution and high X-ray flux is required.
  • the high resolution is achievable because the apparent size of the focal spot 24, when viewed through the exit aperture 34, is much smaller than its real size.
  • the length and width of the focal spot 24 appear to be approximately equal.
  • the interaction of the beam of electrons 6 with the anode 8 results in the formation of scattered electrons (not shown) which are ejected from the anode 8 in a range of directions.
  • the small value of ⁇ results in large numbers of scattered electrons being directed towards the window 31. If the diamond sheet 20 were not present, the window 31 would be subject to severe heating as a result of collisions from the scattered electrons. Scattered electrons are also prevented from reaching the window 31 by the copper plate 15. Because the copper plate 15 has a low transmission coefficient for X-rays, unwanted X-rays having values of ⁇ greater than 20° are prevented from exiting the window 31.
  • the barrier means which comprises the diamond sheet 20 and copper plate 15, prevents scattered electrons from colliding with the window 31 while allowing some of the X-rays 9 to pass from the anode 8 to the window 31.
  • Diamond has a high melting temperature and thus the diamond sheet 20 is able to withstand the heat generated by impact with the scattered electrons.
  • Diamond and copper are both good thermal conductors, so that heat is conducted away from the window 31 thus preventing damage to the window 31 by radiated heat.
  • the use of the barrier means in conjunction with a small incident angle ⁇ results in an X-ray tube 7 which is capable of increased power output without loss of reliability.
EP19960307066 1995-09-27 1996-09-27 Röntgenröhre und Barrierevorrichtung dafür Expired - Lifetime EP0768699B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9519715.8A GB9519715D0 (en) 1995-09-27 1995-09-27 X-ray tube
GB9519715 1995-09-27

Publications (2)

Publication Number Publication Date
EP0768699A1 true EP0768699A1 (de) 1997-04-16
EP0768699B1 EP0768699B1 (de) 2002-06-19

Family

ID=10781368

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19960307066 Expired - Lifetime EP0768699B1 (de) 1995-09-27 1996-09-27 Röntgenröhre und Barrierevorrichtung dafür

Country Status (3)

Country Link
EP (1) EP0768699B1 (de)
DE (1) DE69621894T2 (de)
GB (1) GB9519715D0 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19900467A1 (de) * 1999-01-08 2000-04-20 Siemens Ag Röntgenröhre mit Elektronenfänger
EP1540664A2 (de) * 2002-07-19 2005-06-15 Varian Medical Systems Technologies, Inc. Strahlungsquellen und kompakte strahlungs-abtastsysteme
DE102004030832B4 (de) * 2004-06-25 2007-03-29 Siemens Ag Drehkolben-Röngtenröhre

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102015203459A1 (de) * 2015-02-26 2016-09-01 Siemens Aktiengesellschaft Röntgenröhre

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2665391A (en) * 1950-03-04 1954-01-05 Amperex Electronic Corp X-ray tube having a mica window
US4468802A (en) * 1981-03-02 1984-08-28 Siemens Aktiengesellschaft X-Ray tube
JPS60101848A (ja) * 1983-11-09 1985-06-05 Hitachi Ltd Ｘ線管
EP0319244A2 (de) * 1987-11-30 1989-06-07 Theratronics International Limited Luftgekühlte Metallkeramik-Röntgenröhrenkonstruktion
WO1992003837A1 (en) * 1990-08-24 1992-03-05 Michael Danos X-ray tube

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2665391A (en) * 1950-03-04 1954-01-05 Amperex Electronic Corp X-ray tube having a mica window
US4468802A (en) * 1981-03-02 1984-08-28 Siemens Aktiengesellschaft X-Ray tube
JPS60101848A (ja) * 1983-11-09 1985-06-05 Hitachi Ltd Ｘ線管
EP0319244A2 (de) * 1987-11-30 1989-06-07 Theratronics International Limited Luftgekühlte Metallkeramik-Röntgenröhrenkonstruktion
WO1992003837A1 (en) * 1990-08-24 1992-03-05 Michael Danos X-ray tube

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
"RONTGENROHRE MIT BERYLLIUMFENSTER", NEUES AUS DER TECHNIK, no. 3, 15 September 1989 (1989-09-15), pages 4, XP000071660 *
PATENT ABSTRACTS OF JAPAN vol. 009, no. 251 (E - 348) 8 October 1985 (1985-10-08) *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19900467A1 (de) * 1999-01-08 2000-04-20 Siemens Ag Röntgenröhre mit Elektronenfänger
EP1540664A2 (de) * 2002-07-19 2005-06-15 Varian Medical Systems Technologies, Inc. Strahlungsquellen und kompakte strahlungs-abtastsysteme
EP1540664A4 (de) * 2002-07-19 2009-05-27 Varian Med Sys Tech Inc Strahlungsquellen und kompakte strahlungs-abtastsysteme
DE102004030832B4 (de) * 2004-06-25 2007-03-29 Siemens Ag Drehkolben-Röngtenröhre
US7280639B2 (en) 2004-06-25 2007-10-09 Siemens Aktiengesellschaft Rotary piston x-ray tube with the anode in a radially rotating section of the piston shell

Also Published As

Publication number Publication date
DE69621894T2 (de) 2003-02-20
EP0768699B1 (de) 2002-06-19
GB9519715D0 (en) 1995-11-29
DE69621894D1 (de) 2002-07-25

Similar Documents

Publication Publication Date Title
US5751784A (en) X-ray tube
EP1475819B1 (de) Apparat zur Erzeugung von Röntgenstrahlung mit integralem Gehäuse
US6075839A (en) Air cooled end-window metal-ceramic X-ray tube for lower power XRF applications
EP2740332B1 (de) Strahlungserzeugungsgerät und strahlungsbildgebungsgerät
EP2649635B1 (de) Strahlungserzeugungsgerät und strahlungsbildgebungsgerät
US6005918A (en) X-ray tube window heat shield
EP2740331B1 (de) Strahlungserzeugungsgerät und strahlungsbildgebungsgerät
US10483077B2 (en) X-ray sources having reduced electron scattering
JPH09167586A (ja) Ｘ線管
US5828727A (en) X-ray tube
US5898755A (en) X-ray tube
EP0009946A1 (de) Röntgenröhre
US6111934A (en) X-ray tube with electromagnetic electron beam deflector formed by laminating in planes oriented perpendicularly to the electron beam
JPH11504750A (ja) Ｘ線源
US6236713B1 (en) X-ray tube providing variable imaging spot size
US7260181B2 (en) Enhanced electron backscattering in x-ray tubes
US5909479A (en) Vacuum housing for an electron tube
EP0768699B1 (de) Röntgenröhre und Barrierevorrichtung dafür
JPH0521028A (ja) Ｘ線管
JP7073406B2 (ja) 小型電離放射線源
US7058160B2 (en) Shield structure for x-ray device
JP2015076359A (ja) Ｘ線管装置
US6453011B1 (en) X-ray tube with rotating anode core
JP2002352756A (ja) 回転陽極型ｘ線管装置
JP2014035977A (ja) Ｘ線管装置

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE GB

17P Request for examination filed

Effective date: 19970808

17Q First examination report despatched

Effective date: 19970908

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE GB

REG Reference to a national code

Ref country code: GB

Ref legal event code: FG4D

REF Corresponds to:

Ref document number: 69621894

Country of ref document: DE

Date of ref document: 20020725

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed

Effective date: 20030320

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 20071203

Year of fee payment: 12

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20071214

Year of fee payment: 12

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20080927

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20090401

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20080927