EP0425718A1 - Générateur de rayons X - Google Patents

Générateur de rayons X Download PDF

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Publication number
EP0425718A1
EP0425718A1 EP89120143A EP89120143A EP0425718A1 EP 0425718 A1 EP0425718 A1 EP 0425718A1 EP 89120143 A EP89120143 A EP 89120143A EP 89120143 A EP89120143 A EP 89120143A EP 0425718 A1 EP0425718 A1 EP 0425718A1
Authority
EP
European Patent Office
Prior art keywords
cathode
ray generator
anode
generator according
ray
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
EP89120143A
Other languages
German (de)
English (en)
Other versions
EP0425718B1 (fr
Inventor
Manfred Dr. Schuster
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.)
Bruker AXS Analytical X Ray Systems GmbH
Original Assignee
Siemens AG
Siemens Corp
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 Siemens AG, Siemens Corp filed Critical Siemens AG
Priority to EP89120143A priority Critical patent/EP0425718B1/fr
Priority to DE58908218T priority patent/DE58908218D1/de
Priority to US07/604,951 priority patent/US5052034A/en
Publication of EP0425718A1 publication Critical patent/EP0425718A1/fr
Application granted granted Critical
Publication of EP0425718B1 publication Critical patent/EP0425718B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • 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
    • H01J35/12—Cooling non-rotary anodes
    • H01J35/13—Active cooling, e.g. fluid flow, heat pipes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/08—Targets (anodes) and X-ray converters
    • H01J2235/081—Target material
    • H01J2235/082—Fluids, e.g. liquids, gases

Definitions

  • the invention relates to an X-ray generator according to the preamble of patent claim 1.
  • X-ray tubes for fine structure examinations are known from J. Urlaub, X-ray analysis vol. 1. X-rays and detectors (Siemens, Düsseldorf 1974) pages 71 to 75.
  • the invention has for its object to provide an X-ray generator of the type mentioned, which is simple in construction and has a high brilliance. This object is achieved by an X-ray generator according to claim 1.
  • the brilliance of an X-ray tube can generally be improved because liquid anodes tolerate a higher electron beam power density (no crack formation, better heat dissipation by mixing).
  • the brilliance can also be increased selectively in terms of energy or wavelength by means of X-ray optical effects with a flat beam tap. The prerequisite for this, a smooth anode surface, is ideally met by liquid anodes.
  • claims 2 to 12 relate to configurations of the x-ray generator according to claim 1
  • claims 13 and 15 are directed to a method for operating an x-ray generator.
  • the X-ray generator shown schematically in Fig. 1 consists essentially of a housing formed by the metal wall 1, the beam exit windows 2, the anode support 3/4 and the glass high-voltage bushing 5, a filament 7 arranged in a high vacuum of the housing and connected to voltage supply lines 6 as Cathode and a Wehnelt electrode 8 for focusing the electrons emitted by the incandescent filament 7 onto the anode 9 which is liquid during operation.
  • water 16 or another coolant is added the channel 11 present in the fastening flange 10 is brought up to the anode support base 4 and derived via the channel 12.
  • the coolant circuit between the anode support base 4 and the mounting flange 10 is sealed by an O-ring 13.
  • Performance there is no significant loss of anode liquid 9 to be feared by evaporation, provided that it is cooled sufficiently.
  • the evaporation rate rises considerably at high tube outputs, so that the loss of material can no longer be neglected.
  • There is a dynamic equilibrium between the evaporation rate and the condensation rate since the cooling effect increases with decreasing thickness of the anode liquid 9.
  • the heating and cooling capacity must be set so that the housing pressure does not exceed 10 (-9) bar during operation.
  • Metals with a low melting point FP and a high boiling point KP as well as low vapor pressure and high thermal conductivity are particularly suitable as anode materials, in particular gallium Ga, indium In, tin Sn and their alloys.
  • the melting and boiling points FP and KP of the metals Ga, In and Sn are given in Table 1.
  • the heating by the electron beam is generally so high that no additional heating devices are required to liquefy the anode material.
  • Liquids have a low surface roughness and, if vibrations are avoided, also a low ripple. Since the average roughness of liquids (thermally excited capillary waves) at temperatures T «T KP that are not too high is typically below 1 nm, it is possible to tap the X-rays 14 emitted by the anode 9 at extremely flat angles ⁇ 2 ⁇ 1 °. This is particularly important for increasing the spectral brilliance of the X-ray generator. The size is referred to as spectral brilliance B E
  • Typical values for the exit limit angle are at 0.5 °. Since the X-ray optical properties of the anode surface in the region of extremely small tapping angles (see Eq. (2)) are used to increase the brilliance in the present invention, the flatness of the anode surface must meet the highest requirements.
  • the transmitted intensity is increased in part in the form of diffuse radiation, which does nothing to increase the brilliance.
  • This condition can be derived from the work of B. Vidal and P. Vincent, Applied Optics, 23 No 11 (1984) pp. 1794-1801 and SK Sinha, EB Sirota, S. Garoff and HB Stanley, Phys. Rev. B38 No 4 (1988) pp. 2297-2311.
  • Such a requirement must be met with highly polished solid anodes and in particular with liquid anodes.
  • the gain in brilliance B E with a flat jet tap is based on a geometric effect (projective Reduction of the emitting anode area) and an X-ray optical effect which makes the main contribution (solid angle concentration due to refraction at the anode-vacuum interface).
  • the photon flux can be spectrally selectively amplified or weakened by a suitable choice of the angle ⁇ 2 . This is a decisive advantage over conventional X-ray tubes, in which the photon flow is weakened by angle or spectrally selectively, but never increased, by using the primary or secondary monochromators, filters and diaphragms which improve the signal-background ratio.
  • the nuclear charge number Z and the density p of the anode and the electron inclusion angle ⁇ are also taken into account as parameters (JI Goldstein, Scanning Electron Microscopy and X-Ray Microanalysis; Plenum Press, New York, 1981 pp. 355 ff.) (IV) exp (- zllm k lZ
  • FIG. 4 shows an X-ray generator in which the electrons pass through a funnel-shaped constriction 17 between the filament 7 and the anti-cathode 9, which is liquid during operation.
  • This taper 17, which acts as a hollow anode also has the task of coating the top side 3 of the carrier again after the tube has been transported with the anti-cathode liquid 18 collecting on the tube bottom.
  • the tube is briefly turned over and erected again, so that the liquid 18 hits the upper side 3 of the carrier arranged below the hollow anode and completely wets it.
  • the use of a border arranged on the upper side 3 of the support and projecting in the direction of the cathode 7 is out of the question since this would hinder the desired flat steel tap.
  • the exemplary embodiment according to FIG. 5 shows an X-ray generator in which the electrons emitted by the cathode 7 and accelerated in the direction of the hollow anode 17 pass through a window 20, which seals the housing 19 in a vacuum-tight manner, in order to dispose of the anti-cathode liquid arranged outside the housing 19 on the water-cooled upper side 3 of the carrier 9 to generate brake radiation and characteristic X-ray radiation 14.
  • the height d of the spacer 21 screwed to the housing 19, the anti-cathode support 3 and the fastening flange 10 can be chosen to be very small (d ⁇ 1 mm), so that no appreciable electron absorption takes place in the atmosphere.
  • the absorption in the electron exit window 20 also remains very low when using 0.5 .mu.m thick quantum as window material (to be obtained from Kevex Cooperation, Foster City CA). Since a low vapor pressure does not have to be required for the materials which can be used as the anti-cathode, sodium and mercury can also be considered as anti-cathode materials in addition to galium, indium and tin.
  • the advantage of the beam generator described here is in particular that the low-energy spectral components can also be used experimentally.
  • the exemplary embodiment according to FIG. 6 shows an X-ray generator, the anode of which is formed by an electrically conductive liquid 9 with a low vapor pressure.
  • a Faraday pump 23 is provided in the insulating body-guided anode liquid 9, the horseshoe magnet 24 of which generates a magnetic field oriented perpendicular to the desired flow direction 25.
  • An electrical current flowing between the electrodes 26 perpendicular to the magnetic field and flow direction 25 ensures the Lorentz force accelerating the anode liquid 9.
  • the heated anode liquid 9 is cooled in a heat exchanger 27.
  • the cooling water enters through the opening 28 in the heat exchanger 27 in order to flow off again at the outlet 29.
  • the nozzle 30 (Laval nozzle) provided in the channel of the anode liquid 9 serves to adapt the magnetic circulation pressure to the gas pressure p ⁇ (10 (-9) bar present in the housing, in order thereby to achieve a smooth interface between the nozzle 30 and the point of impact 31 of the To ensure electron beam flowing anode liquid 9. As mentioned at the beginning, this is an indispensable prerequisite for the applicability of the beam tap at the critical angle of the total reflection.
  • the arrangement consisting of the ceramic insulating body 22, the cathode 7 and the focusing unit 8 (Wehnelt electrode, focusing trough or Pierce electrode) is located in an evacuated housing (not shown), the vacuum-tight voltage and cooling water feedthroughs and windows for the exit at an angle a 2 has tapped x-rays 14.
  • the liquid 9 heated by the electron beam is exchanged very quickly and supplied to the cooling unit 27.
  • the comparatively low thermal conductivity of the anode materials used, gallium, indium and tin, does not have any disadvantageous effects, since the anode liquid 9 stores the heat and releases it very quickly as a result of the mixing in the backflow region.
  • the electron beam thus constantly strikes the liquid flowing in with cooling, as a result of which the permissible power density of the electron beam can be significantly increased compared to a liquid anode which has not been circulated.
  • the anode liquid 9 is circulated with the aid of a rotating drum 32.
  • An electric motor 36 which is rigidly connected to the evacuated housing 34/35 via the carrier 33, is used as the drive unit, a coupling 38 consisting of two opposite magnets 37 each transmitting the rotary movement of the outer cylinder 39 to the drum 32.
  • the rotating drum 32 with the paddle wheels 40 exerts pressure on the anode liquid 9 flowing off at the open end faces, so that it starts to move in the pipeline 41. It flows through the heat exchanger 42 and the central tube 41 in order to exit again via the diffuser 43.
  • the anode liquid 9 is gripped by the rotating drum 32 and pressed against the inner wall by the centrifugal force. It then flows off again via the paddle wheels 40, so that the pressure required for the recirculation builds up again.
  • the electrons emitted by the cathode 7 are accelerated by a high voltage supplied via the connections 44 and focused on the anode liquid 9 with the aid of a Pierce or Wehnelt electrode 8. Here they generate braking radiation and characteristic X-rays 14, which are picked up again at a flat angle a 2 and coupled out through the window 2.
  • a vacuum pump (not shown in FIG.
  • a turbomolecular pump in particular a turbomolecular pump, is used to evacuate the housing, which consists of two parts 34/35 and is rigidly connected to the motor mount by a screw connection, and which sucks off the residual gas via the connection piece 45.
  • a vacuum seal in particular a gold wire seal, is provided between the two housing parts 34 and 35.
  • the invention is of course not limited to the exemplary embodiments described. It is thus readily possible to replace the drum described above with a rotating disk, the anode liquid emerging from a hollow axis carrying the disk and wetting the disk surface.

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • X-Ray Techniques (AREA)
EP89120143A 1989-10-30 1989-10-30 Générateur de rayons X Expired - Lifetime EP0425718B1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP89120143A EP0425718B1 (fr) 1989-10-30 1989-10-30 Générateur de rayons X
DE58908218T DE58908218D1 (de) 1989-10-30 1989-10-30 Röntgenstrahlerzeuger.
US07/604,951 US5052034A (en) 1989-10-30 1990-10-29 X-ray generator

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP89120143A EP0425718B1 (fr) 1989-10-30 1989-10-30 Générateur de rayons X

Publications (2)

Publication Number Publication Date
EP0425718A1 true EP0425718A1 (fr) 1991-05-08
EP0425718B1 EP0425718B1 (fr) 1994-08-17

Family

ID=8202077

Family Applications (1)

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EP89120143A Expired - Lifetime EP0425718B1 (fr) 1989-10-30 1989-10-30 Générateur de rayons X

Country Status (2)

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EP (1) EP0425718B1 (fr)
DE (1) DE58908218D1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005096341A1 (fr) * 2004-03-30 2005-10-13 Yxlon International Security Gmbh Module anodique pour source de rayons x a anode a metal liquide, et dispositif d'emission de rayons x comprenant un module anodique

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE890246C (de) * 1940-03-03 1953-09-17 Heinrich Dr Med Chantraine Roentgenroehre mit einer aus einer umlaufenden metallischen Fluessigkeit, z. B. Quecksilber, bestehenden Anode
US2665390A (en) * 1951-08-18 1954-01-05 Gen Electric Anode target
US3646380A (en) * 1968-08-17 1972-02-29 Philips Corp Rotating-anode x-ray tube with a metal envelope and a frustoconical anode
FR2108149A1 (en) * 1970-07-29 1972-05-19 Alsacienne Atom Liquid metal-cooled cell - for equipment receiving a continuous heat flux
EP0300808A2 (fr) * 1987-07-24 1989-01-25 Hitachi, Ltd. Tube à rayons X et procédé pour la production de rayons X dans le tube

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE890246C (de) * 1940-03-03 1953-09-17 Heinrich Dr Med Chantraine Roentgenroehre mit einer aus einer umlaufenden metallischen Fluessigkeit, z. B. Quecksilber, bestehenden Anode
US2665390A (en) * 1951-08-18 1954-01-05 Gen Electric Anode target
US3646380A (en) * 1968-08-17 1972-02-29 Philips Corp Rotating-anode x-ray tube with a metal envelope and a frustoconical anode
FR2108149A1 (en) * 1970-07-29 1972-05-19 Alsacienne Atom Liquid metal-cooled cell - for equipment receiving a continuous heat flux
EP0300808A2 (fr) * 1987-07-24 1989-01-25 Hitachi, Ltd. Tube à rayons X et procédé pour la production de rayons X dans le tube

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
JAPANESE JOURNAL OF APPLIED PHYSICS, SUPPLEMENTS. vol. 24, no. 6, Juni 1985, TOKYO JA Seiten L387 - L390; S Hasegawa et al.: "Chemical analysis of surfaces by total-reflection-angle X-ray spectroscopy in RHEED experiments (RHEED-TRAXS)" *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005096341A1 (fr) * 2004-03-30 2005-10-13 Yxlon International Security Gmbh Module anodique pour source de rayons x a anode a metal liquide, et dispositif d'emission de rayons x comprenant un module anodique

Also Published As

Publication number Publication date
EP0425718B1 (fr) 1994-08-17
DE58908218D1 (de) 1994-09-22

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