EP0126668B1 - Drehanoden-Röntgenröhre - Google Patents
Drehanoden-Röntgenröhre Download PDFInfo
- Publication number
- EP0126668B1 EP0126668B1 EP84400848A EP84400848A EP0126668B1 EP 0126668 B1 EP0126668 B1 EP 0126668B1 EP 84400848 A EP84400848 A EP 84400848A EP 84400848 A EP84400848 A EP 84400848A EP 0126668 B1 EP0126668 B1 EP 0126668B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- anode
- cathode
- hollow
- hollow anode
- tube according
- 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.)
- Expired
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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
- H01J35/101—Arrangements for rotating anodes, e.g. supporting means, means for greasing, means for sealing the axle or means for shielding or protecting the driving
- H01J35/1017—Bearings for rotating anodes
- H01J35/103—Magnetic bearings
Definitions
- the invention relates to an X-ray tube with a rotating anode, in which the rotation of the anode is effected by magnetic bearings.
- High power X-ray tubes generally use a rotating anode, the rotation of which is still very commonly ensured by mechanical bearings. Given the high rotational speed, which can reach 20,000 revolutions per minute, these mechanical bearings exhibit rapid wear, and are frequently the cause of the decommissioning of X-ray tubes.
- An important improvement consists in mounting the rotating anode with magnetic bearings. These generally include electromagnets mounted two by two in opposition, which create magnetic fields under the influence of which a rotor, integral with the rotating anode which it ensures rotation, is kept in equilibrium; the rotating anode and the mechanical parts which accompany it in rotation, thus no longer have mechanical contact with the rest of the X-ray tube.
- thermo-emissive cathodes mechanically linked to the rotating anode; these electrons being captured by fixed anodes.
- One of the main difficulties is then to supply, to these rotated cathodes, the energy necessary to raise their temperature to a level sufficient to meet the laws of thermoelectronic emission.
- This patent application describes the arrangement of an X-ray tube with a rotating anode, provided with magnetic bearings and means for flowing, without contact, the anode current.
- a rotating anode secured to a rotor is mounted on magnetic bearings.
- the rear of the rotor has two cathodes rotating around an axis, on which an anode is arranged.
- the cathodes comprise windings cooperating during the rotation of the rotary anode, with a plurality of excitation coils; these excitation coils being distributed over the periphery of the tube and inducing in the rotating windings, the heating voltage of the cathodes.
- Another French patent application published under No. 2,494,497, also describes an X-ray tube, comprising a rotating anode with magnetic bearings, and means for discharging the anode current without contacts.
- An auxiliary cathode is placed in the central position of the anode, and a heating filament, in a fixed position, is placed in front of the auxiliary cathode.
- An auxiliary anode in the form of a tube or ring surrounds the heating filament and collects the electrons emitted by the auxiliary cathode.
- One of the drawbacks of this solution is that the dimensions of the heating filament are limited by the diameter of the auxiliary ring anode, and therefore it is difficult to obtain the desired heating power.
- heating intended to flow an anode current is obtained by a combination of much simpler means, which do not have the above-mentioned drawbacks.
- the present invention relates to an X-ray tube with a rotating anode mounted on magnetic bearings, making it possible to flow the anode current without contact; this being obtained in the X-ray tube according to the invention in a simpler and less expensive way than according to the prior art, thanks in particular to the use of a thermo-emissive cathode and a new arrangement making it possible to heat it by thermal rays.
- an X-ray tube comprising a rotating anode mounted on magnetic bearings and at least one device intended to drain the anode current from the tube, is characterized in that this device comprises in a fixed position a hollow anode, inside of which a cathode is coupled in rotation to the rotating anode, the hollow anode being associated with heating means external to the hollow anode, the hollow anode being connected to the positive pole of the high voltage, the cathode being electrically connected to the rotating anode so as to ensure the passage of the anode current.
- the X-ray tube 1 shown in FIG. 1, comprises a vacuum-tight envelope 2-3, constituted in the nonlimiting example described by an insulating central part 2 and, by end parts 3 formed by thin metal shirts; a main cathode 5 carried by the insulating central part 2, is intended to supply an electron beam (not shown) whose impact on a rotating anode 6 causes X-radiation.
- the rotating anode 6 is carried by a metal shaft 7, integral with a rotor 8; this rotor 8 forms with. a stator 9 located outside the casing 2-3, a motor ensuring the rotation of the rotary anode 6 around a longitudinal axis 10.
- the shaft 7 is also secured at its ends 4, to rotating parts 11, 12, conical in the nonlimiting example described, and which constitute the suspended parts of magnetic bearings 11-13, 12-14; active parts 13, 14 of these magnetic bearings being located outside the envelope 2-3.
- guard bearings 25 situated opposite the ends 4 of the shaft 7, with which these bearings 25 are in contact only in the event of failure of the magnetic suspension .
- the tube 1 also includes a device 40, represented in a frame in dotted lines, located inside the envelope 2-3 and intended, in operation, to drain the anode current from the tube 1.
- a device 40 represented in a frame in dotted lines, located inside the envelope 2-3 and intended, in operation, to drain the anode current from the tube 1.
- This device 40 comprises a metal axis 15 extending the shaft 7 along the longitudinal axis 10, on the side of the rotor 8, and carrying a cathode 16.
- the cathode 16 of spherical shape, in the nonlimiting example described, is centered on the longitudinal axis 10; it is electrically connected by the metal axis 15 and the shaft 7 to the rotating anode 6, and is in operation brought to the same potential as the latter.
- a hollow anode 17, also of spherical shape in the non-limiting example described, is held in a fixed position and centered around the cathode 16, by a metal support 18 secured to an insulating support 19.
- the hollow anode 17 comprises a hole 20 intended for the passage of the metal axis 15, thus allowing the movement of the cathode 16, which is coupled in rotation to the rotating anode 6; the rotation of the cathode 16 taking place inside the hollow anode 17, and, like that of the rotating anode 6, around the longitudinal axis 10 according to arrow 29.
- a heating filament 21 supported in a conventional manner by means not shown and connected to two sealed bushings 22, 23, which is provided with the insulating support 19; the latter also vacuum-tight, has a third bushing 24, electrically connected to the metal support 18 of the hollow anode 17.
- the high voltage necessary for the operation of the tube 1 is supplied in a known manner by a high voltage generator 31.
- a positive + HT output of this high voltage is connected to the end portions 3, as well as to the third crossing 24, to be applied to the hollow anode 17;
- a negative output - HT of the generator 31 is connected in a conventional manner by a fourth bushing 35 to the main cathode 5, the latter also comprising in known manner and not shown, heating connections.
- the heating filament 21 heats the hollow anode 17, which constitutes a practically closed enclosure in which the cathode 16 is heated in its turn as in an oven, by the thermal radiation of the hollow anode 17.
- the device 40 may include, as in the nonlimiting example described, a partially shown thermal reflector 32, enveloping the heating filament 21.
- the cathode 16 electrically connected to the rotating anode 6 then generates electrons which are captured by the hollow anode 17, which is connected to the positive + HT pole of the high voltage; the intensity of the electronic current thus generated is the same as that of the electron beam emitted by the main cathode 5, towards the rotating anode 6.
- the anodic current of the tube 1 is thus passed with a small difference in voltage between the polarity positive + HT of the high voltage, and the value + HT 'established at the rotating anode 6.
- the thermal energy supplied by the heating filament 21 is transferred via the hollow anode 17 to the cathode 16 to constitute the energy necessary for the extraction of the electrons.
- This energy transfer can be made more efficient by appropriate adaptations of the cathode and hollow anode 16, 17, and by the use of a second voltage source, as explained with reference to Figure 2; for better clarity of this FIG. 2, the representation of the X-ray tube according to the invention is limited in order to better show the device 40.
- the cathode 16 can be hollow as in the example shown in Figure 2, where it has the shape of a sphere; this form may be different as explained in the following description.
- the cathode 16 has a wall 26, having a small thickness e, and preferably consisting of a refractory material such as tantalum or thoriated tungsten; this wall 26 can also be covered on its outer surface 33, to increase the emissivity in electrons, of lanthanum boride for example (not shown).
- the hollow anode 17 is formed by two half-spheres 27, 28 assembled made of graphite, pyrolitic graphite for example, or also of a refractory material such as tungsten or molybdenum.
- the X-ray tube according to the invention comprises a power source constituted by a low-voltage DC generator 45.
- a positive output V + of this low voltage generator 45 is connected to the hollow anode 17 and also to the positive pole of the high voltage + HT; a negative output -V being it connected to one of the ends of the heating filament 21, to the bushing 23 for example.
- the DC voltage delivered by this low voltage generator 45 determines, between the heating filament 21 and the hollow anode 17, a potential difference.
- the hollow anode 17, being positive with respect to the heating filament 21 is subjected to the bombardment of electrons emitted by this filament; this electron bombardment of the hollow anode 17 causes the latter to have a high temperature which determines its thermal radiation in the direction of the cathode 16.
- This latter mode of heating the hollow anode 17 can be used either alone or combined with that previously described, the heat shield 32, not shown in FIG. 2, which can be kept in this variant.
- the hollow anode 17 is made of graphite
- its outer surface 34 is preferably covered with a highly reflective metal deposit (of the so-called mirror-polished type for example) .
- its external surface 34 can also be reflective (mirror-polished), its internal surface 36 being covered with a material (not shown) with high thermal radiation power.
- This description constitutes a nonlimiting example of an X-ray tube according to the invention, capable of flowing the anode current from the tube 1, without contact between the fixed parts and the rotating parts of this tube.
- a device 40 notably includes an electron-emitting cathode 16, which receives the electron extraction energy thanks to the radiation of a hollow anode 17 intended to capture these electrons.
- the shape of this cathode 16 and of this hollow anode may be different from that shown in FIGS. 1, 2, the main thing being that the cathode 16, integral with the rotating anode 6, is located in an enclosure, heated, constituting a hollow anode 17. Nevertheless, the shapes of the hollow anode 17 and of the cathode 16 are preferably adapted so that their surfaces 36, 33, facing each other, are at a distance D as constant as possible.
- the hollow anode 17 and the cathode 16 can also have a conical or cylindrical shape as shown in FIG. 3.
- This arrangement of the hollow anode 17 and the cathode 16 also makes it possible to use heating means different from those constituted by the heating filament 21 and of low-voltage generator 45; the heating of the cathode 16 being obtained by the thermal radiation of the hollow anode 17. It should also be noted that the combination of means of the device 40 can also be located at one or the other of the ends 3 of the 'envelope 2-3 or simultaneously at these two ends.
- the device 40 can also be adapted to different positions as shown in the nonlimiting example of FIG. 4, where this device, already explained, is represented by a rectangle in dotted lines.
- FIG. 4 shows an X-ray tube 1 according to the invention, the magnetic bearings 11-13, 12-14 of which are situated on the same side of the rotating anode 6.
- the tube 1 its envelope is made up of a metal end part 3, and of an insulating part 2, on the side of which are contained the rotating anode 6 and the main cathode 5.
- the part of metal end 3 being brought to earth potential, as well as the magnetic bearings 11-13,12-14 and the rotor 8, by conventional means and not shown; the guard bearings 25 being arranged around a fixed shaft 39, disposed in the rotor 8 along the longitudinal axis 10.
- the rotor 8 rotates the rotary anode 6 around the longitudinal axis 10, by means of an insulating shaft 38, the latter being made of a refractory material and highly electrical insulator, such as for example alumina , or ceramic as in the example described.
- the device 40 serving to drain the anode current is in the immediate vicinity of the rotating anode 6, to which it is mechanically and electrically connected thanks to the metal axis 15; cathode 16, not shown in FIG. 4, being coupled in rotation to the rotating anode 6 as previously explained.
- the internal electrical connections (not shown), necessary for the device 40 are routed, out of the tube 1, by a sheath 37 made of a refractory material with very low coefficient of expansion, such as for example alumina or ceramic ; these internal connections leading to the crossings 22, 23, 24 of the base 19.
- the operation of the device 40 remains, in this arrangement, the same as previously explained, as well as its external electrical connections not shown in FIG. 4; an exception however being that in this last version, the end part 3 is at ground potential, and is therefore no longer connected to + HT.
- An X-ray tube 1 according to the invention is applicable to all fields of radiology, to which it provides a simple, reliable and economical solution, by means of the device 40 serving to flow the anode current without contact.
Landscapes
- X-Ray Techniques (AREA)
Claims (9)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR8307610A FR2545649B1 (fr) | 1983-05-06 | 1983-05-06 | Tube radiogene a anode tournante |
FR8307610 | 1983-05-06 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0126668A1 EP0126668A1 (de) | 1984-11-28 |
EP0126668B1 true EP0126668B1 (de) | 1987-08-19 |
Family
ID=9288667
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP84400848A Expired EP0126668B1 (de) | 1983-05-06 | 1984-04-26 | Drehanoden-Röntgenröhre |
Country Status (4)
Country | Link |
---|---|
US (1) | US4651336A (de) |
EP (1) | EP0126668B1 (de) |
DE (1) | DE3465550D1 (de) |
FR (1) | FR2545649B1 (de) |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2539193B2 (ja) * | 1984-12-20 | 1996-10-02 | バリアン・アソシエイツ・インコーポレイテッド | 高強度x線源 |
JPS6276246A (ja) * | 1985-09-30 | 1987-04-08 | Toshiba Corp | 回転陽極形x線管 |
DE3540303A1 (de) * | 1985-11-13 | 1987-05-14 | Siemens Ag | Drehanoden-roentgenroehre |
FR2599555A1 (fr) * | 1986-06-03 | 1987-12-04 | Thomson Cgr | Tube radiogene tournant |
GB2346007B (en) | 1999-01-21 | 2004-03-03 | Imaging & Sensing Tech Corp | Getter flash shield |
US8284899B2 (en) * | 2007-11-21 | 2012-10-09 | Varian Medical Systems, Inc. | X-ray tube having a focal spot proximate the tube end |
DE102008062671B4 (de) * | 2008-12-17 | 2011-05-12 | Siemens Aktiengesellschaft | Röntgeneinrichtung |
WO2013038287A1 (en) * | 2011-09-13 | 2013-03-21 | Koninklijke Philips Electronics N.V. | X-ray radiation with multiple photon energies |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2262757C3 (de) * | 1972-12-21 | 1979-06-21 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | RöntgenrShrendrehanodenlagerung |
DE3043046A1 (de) * | 1980-11-14 | 1982-07-15 | Siemens AG, 1000 Berlin und 8000 München | Drehanoden-roentgenroehre |
DE3043670A1 (de) * | 1980-11-19 | 1982-07-08 | Siemens AG, 1000 Berlin und 8000 München | Drehanoden-roentgenroehre |
-
1983
- 1983-05-06 FR FR8307610A patent/FR2545649B1/fr not_active Expired
-
1984
- 1984-04-26 DE DE8484400848T patent/DE3465550D1/de not_active Expired
- 1984-04-26 EP EP84400848A patent/EP0126668B1/de not_active Expired
- 1984-04-27 US US06/604,815 patent/US4651336A/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
EP0126668A1 (de) | 1984-11-28 |
US4651336A (en) | 1987-03-17 |
FR2545649B1 (fr) | 1985-12-13 |
DE3465550D1 (en) | 1987-09-24 |
FR2545649A1 (fr) | 1984-11-09 |
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