WO1987006055A1 - Tube photoelectrique a rayons-x - Google Patents

Tube photoelectrique a rayons-x Download PDF

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Publication number
WO1987006055A1
WO1987006055A1 PCT/US1987/000418 US8700418W WO8706055A1 WO 1987006055 A1 WO1987006055 A1 WO 1987006055A1 US 8700418 W US8700418 W US 8700418W WO 8706055 A1 WO8706055 A1 WO 8706055A1
Authority
WO
WIPO (PCT)
Prior art keywords
anode
tube
envelope
vacuum
stationary
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.)
Ceased
Application number
PCT/US1987/000418
Other languages
English (en)
Inventor
Weston A. Anderson
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
Publication of WO1987006055A1 publication Critical patent/WO1987006055A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/24—Tubes wherein the point of impact of the cathode ray on the anode or anticathode is movable relative to the surface thereof
    • 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
    • H01J35/06—Cathodes
    • H01J35/065—Field emission, photo emission or secondary emission cathodes
    • 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
    • H01J2235/161—Non-stationary vessels
    • H01J2235/162—Rotation

Definitions

  • the invention pertains to rotating-target X-ray tubes for generating high-power, pulsed and continuous fluxes of X-rays.
  • the classic X-ray tubes have a thermionic cathode at one end and a fixed metallic anode at the other. Their power capacity is limited by the conductive cooling of the anode target by the electron beam which, must be tightly focused to provide a high-definition image.
  • a later advance was the rotating-target tube in which the target is the surface of a metal disc spinning rapidly on bearings inside the vacuum envelope and driven by the rotor of an electric induction motor whose stator is outside the envelope.
  • the rotating anode spreads the heat over an annular area of the target and provides much higher power for a short operating time, as in medical radiography.
  • the ultimate cooling of the anode is mostly by thermal radiation in the high vacuum, so these tubes are inadequate for high-duty or C operation. One has to wait for the- massive anode to slowly cool.
  • the cathode is held stationary off-axis by hanging on bearings from the rotating envelope and being held stationary by a magnetic or gravitational field.
  • a purpose of the invention is to provide an X-ray tube capable of generating a high-power flux of radiation with a high duty cycle or CW operation, as desired for medical radiology or X-ray photolithography.
  • the whole vacuum envelope rotate with the anode.
  • the anode being part of the vacuum envelope, it can be cooled from outside by liquid or air.
  • the cathode also rotates. It is an axially symmetric band of photocathode s-urface which is illuminated by a focused, stationary spot of light entering the envelope through an axially symmetric, transparent window part of the vacuum envelope. Photoelectrons from the cathode are focused, as by a stationary magnetic field, onto a small stationary spot on the anode.
  • FIG. 1 is an isometric sketch of an embodiment of the invention.
  • FIG. 2 is an axial section of part of a different embodiment.
  • FIG. 3 is an axial section of an alternative construction of the rotor.
  • FIG. 4 is an end view of an alternative arrange- ment of the fins of FIG. 3.
  • FIG. 1 shows a mechanically simple embodiment of the invention.
  • An axially symmetric rotor 10 constitutes the vacuum envelope and also the 5 electrodes of the tube. It is connected to opposed axial shafts 12,13 which constitute the high-voltage connections to the tube. Shafts 12,13 are rotatable on one or more bearings 14 and driven by a motor 16. Rotor 10 comprises two end-plates 18,20 joined by a
  • An annular section 24 of end-plate 20 is of optically transparent material such as glass or sapphire hermetically sealed to the adjacent metal parts.
  • An external stationary light source 26 emits a beam of
  • Electrons 34 are focused, as by a stationary, generally axial magnetic field (not shown) onto a stationary anode spot 36 on
  • X-rays 40 emitted from spot 36 pass out through a vacuum window, which in this embodiment is a band on cylindrical rotor element 22. Cylinder 22 may also be the high-voltage
  • cathode end-plate 20 and anode end-plate 18. It would typically be of high-alumina ceramic which has good X-ray transmissivit . Heat from anode plate 18 is carried off by the surrounding air. Alternatively, liquid coolant may be circulated
  • FIG. 2 illustrates a slightly different embodiment.
  • the photocathode surface 33 is formed as an annular ring on end-plate 18' which is the cathode electrode in this embodiment.
  • Light 28' is focused with the help of a mirror 42 onto a stationary region 32' on photocathode 33.
  • Electrons 34' are drawn back to end-plate 20' which is now the anode electrode. They are focused onto a stationary spot 36" on a rotating conical anode surface 38 which is slanted as well known in the art for maximum radiated flux in the desired direction.
  • the electrons are focused by an essentially axial magnetic field produced by an external coil 44, as known in the art of electron optics. Alternatively, electrostatic or proximity focusing may be used.
  • FIG. 3 is a section of an alternative rotor with different constructional features.
  • Window 24 as of glass, is sealed between coaxial, axially extending flanges 46,47 of metal adapted for sealing to glass, such as certain iron-nickel-cobalt alloys sold under trademarks such as "Kovar”.
  • High-voltage insulating cylinder 22" is sealed by brazing its metalized ends to the ends of thin, axial, metallic flanges 48 on the end-plates 18 , , ,20' '. This accora- modates differences in thermal expansion.
  • metallic protruberances 50 are thermally bonded to anode end-plate 20.
  • Protu ⁇ berances 50 may be coaxial cylindrical fins. Alternatively they may be peripherally separated to enhance fluid turbulence as they rotate.
  • the protuberances may be shaped in the form of spiral fins 50' that simul ⁇ taneously provide increased thermal contact between the fluid and the x-ray anode and also provide pumping action to the adjacent fluid to continuously bring fresh cool fluid into the region of thermal contact.
  • calculations will be given as to possible operating parameters of the inventive tube.
  • a medical X-ray system such as a CAT scanner, one could use an electron current of 200 ma at 100 KV. The power in the light flux would have to be
  • I is the photoemitted current
  • 0.2 amperes h is Plancks' constant
  • 6.6 x 10 * 34 joules/second is the light frequency, equal to C/ ⁇ where C is the velocity of light, 3 x 10 8 meters /second
  • Xenon arc lamps have power efficiencies from 25 to 40%, with about 10% of the radiation having a wavelength below 0.7 microns and thus effective for photoemission (Reference "Solid State Laser
  • a commercially available 500W Xenon lamp would be adequate .
  • the window and/or one of the electrodes may be on an axially- extending surface of the vacuum chamber instead of on a flat end.
  • the transparent window may be part or all of the insulating portion of the vacuum envelope. It is only necessary that the axial symmetry be maintained. The invention is to be limited only by the following claims and their legal equivalents.

Landscapes

  • X-Ray Techniques (AREA)

Abstract

La capacité de puissance moyenne d'un tube générateur de rayons X à anode rotative est limitée par le lent refroidissement par rayonnement de l'anode. On élimine ce désavantage dans la présente invention en faisant tourner l'enveloppe sous vide complet (22'), permettant ainsi à la chaleur d'être conduite directement dans l'air ou dans un liquide en circulation. La cathode (33) et l'anode (36') sont placées de façon à effectuer une révolution autour de l'axe. Une source fixe de rayons X est produite par focalisation d'un point lumineux fixe (32') sur une photocathode rotative (33). Les photoélectrons (34') sont retirés et focalisés sur un point fixe situé sur l'anode rotative, afin de produire une source fixe de rayons X (40').
PCT/US1987/000418 1986-03-25 1987-02-27 Tube photoelectrique a rayons-x Ceased WO1987006055A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US84396086A 1986-03-25 1986-03-25
US843,960 1986-03-25

Publications (1)

Publication Number Publication Date
WO1987006055A1 true WO1987006055A1 (fr) 1987-10-08

Family

ID=25291425

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1987/000418 Ceased WO1987006055A1 (fr) 1986-03-25 1987-02-27 Tube photoelectrique a rayons-x

Country Status (3)

Country Link
EP (1) EP0261199A4 (fr)
JP (1) JPS63502942A (fr)
WO (1) WO1987006055A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0740847A4 (fr) * 1994-01-21 1998-02-04 Photoelectron Corp Source de rayons x a rayonnement conforme
WO1998005056A1 (fr) * 1996-07-30 1998-02-05 Varian Associates, Inc. Tube photoelectrique a rayons x
WO1998057349A1 (fr) * 1997-06-13 1998-12-17 Commissariat A L'energie Atomique Tube a rayons x comportant une source d'electrons a micropointes et des moyens de guidage magnetique

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2111412A (en) * 1928-12-08 1938-03-15 Gen Electric X-ray apparatus
US2900543A (en) * 1955-05-04 1959-08-18 Max Planck Inst Fur Biophysik X-ray tube
US4165472A (en) * 1978-05-12 1979-08-21 Rockwell International Corporation Rotating anode x-ray source and cooling technique therefor
US4606061A (en) * 1983-12-28 1986-08-12 Tokyo Shibaura Denki Kabushiki Kaisha Light controlled x-ray scanner

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2111412A (en) * 1928-12-08 1938-03-15 Gen Electric X-ray apparatus
US2900543A (en) * 1955-05-04 1959-08-18 Max Planck Inst Fur Biophysik X-ray tube
US4165472A (en) * 1978-05-12 1979-08-21 Rockwell International Corporation Rotating anode x-ray source and cooling technique therefor
US4606061A (en) * 1983-12-28 1986-08-12 Tokyo Shibaura Denki Kabushiki Kaisha Light controlled x-ray scanner

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP0261199A4 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0740847A4 (fr) * 1994-01-21 1998-02-04 Photoelectron Corp Source de rayons x a rayonnement conforme
WO1998005056A1 (fr) * 1996-07-30 1998-02-05 Varian Associates, Inc. Tube photoelectrique a rayons x
WO1998057349A1 (fr) * 1997-06-13 1998-12-17 Commissariat A L'energie Atomique Tube a rayons x comportant une source d'electrons a micropointes et des moyens de guidage magnetique
FR2764731A1 (fr) * 1997-06-13 1998-12-18 Commissariat Energie Atomique Tube a rayons x comportant une source d'electrons a micropointes et des moyens de focalisations magnetique

Also Published As

Publication number Publication date
EP0261199A4 (en) 1991-04-10
JPS63502942A (ja) 1988-10-27
EP0261199A1 (fr) 1988-03-30

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