GB2212975A

GB2212975A - Rotating anode X-ray tube

Info

Publication number: GB2212975A
Application number: GB8827828A
Authority: GB
Inventors: Hisakazu Ishio
Original assignee: RIGAKU DENKI KK
Current assignee: RIGAKU DENKI KK
Priority date: 1987-11-30
Filing date: 1988-11-29
Publication date: 1989-08-02
Also published as: JPH0186156U; DE3840398C2; FR2627900B1; GB8827828D0; DE3840398A1; FR2627900A1

Description

r" 2 2 1 2 9 7) p 0 Rotating Anode X-Ray Tube The present invention

relates to a rotating anode X-ray tube, and more particularly to an improvement of a rotating anode X-ray tube in which two kinds of X-rays having different wavelength characteristics from one another can be generated simultaneously.

In general, a rotating anode X-ray tube for use in a diffractometer or the like has a rotating cylindrical- shaped anode or target. The anode is arranged so that its peripheral surface con-Fronts an end face ofa cathode. When thermoelectrons emitted from the cathode the rotating Jmpinge upon the peripheral surface o'. anode, the X-rays are generated and emitted from the anode surface in various directions. In the X-ray tube, the X-rays thus emitted at a small angle with respect to a rotatinc axis of the anode are taken out and utilized, whereby the X-rays having high X- ray intensity can be taken out from a source of small effective area. 20 However in the conventional rotating anode X-ray tube, the X-rays taken out of windows usually have only one kind of wavelength characteristics. There is another known type of a rotating anode X-ray tube in which a plurality of materials are attached at different positions around the anode surface. In the rotating X-ray tube of this type, X-rays having different wavelength characteristics can be generated and taken out by changing over the anode position upon which the thermoelectrons impinge. However, again with this type X-rays having only one wavelength characteristic are generated and taken out at any instant and X-rays with different wavelength characteristics are not generated simultaneously.

According to this invention a rotating anode X-ray tube comprises:

a casing having at least two exit windows for the X-rays disposed opposite one another, the casing containing an interior space; an anode rotatable about an axis, within the "ormed of two truncated conical interior space and 'L portions which provide generatrixes and peripheral surfaces, each of said generatrixes being inclined by a small angle in opposite directions with respect to the rotational axis, and the peripheral surfaces of the two portions being made of different materials; and, cathode means provided in confrontation with the or emitting two electron beams in d' anode j-fferent upon their directions, the electron beams being incident respective peripheral surrEaces, whereby the two kinds of X-rays generated at the two peripheral surfaces leave the casing through their respective exit windows.

With the tube in accordance with this invention two :erent wavelenath kinds of X-rays havincr diff characteristics from one another can be simultaneously generated and taken out of the two exit windows.

A particular example of an X-ray tube in accordance with this invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a partly sectioned side elevation; Figure 2 is a perspective view as viewed from the line II-II shown in Figure 1; and, Figure 3 is a diagrammatic side elevation of a diffractometer incorporating the X-ray tube.

ir 3 - Fig. I illustrates a rotating X-ray tube according to one embodiment of the present invention.

A rotating X-ray tube is provided with a fluid tight metal casing 1 in the form of a polygon pillar. The fluid tight metal casing I is connected to a vacuum pump(not shown in Fig. 1), and an interior of the casing I is maintained in a condition evacuated to such a vacuum degree that its electrical characteristics are essentially unaffected by the presence of residual gas or vapor. The side wall of the casing I is provided lowith a bearing 2 by which a rotating shaft 3 is rotatably supported. The rotating shaft 3 has one end connected to a pulley 4 carrying an endless belt 5. The endless belt 5 is mounted over a driving pulley (not shown in Fig. 1) connected to a driving source such as a motor. A rotating anode 6 is fixedly l5provided at another end of the rotating shaft 3, and is rotated together with a rotation of the shaft 3.

The rotating anode 6 is in the form of double truncated cones in which each of larger diameter areas is coupled together in order to provide substantially barrel like profile. The peripheral surfaces 7a,Sa of two truncated cone portions 7,8 are made of materials different from each other such as copper and molybdenum. Each generatrix of truncated cone portions 7,8 is inclined about 6 degrees with respect to a rotating axis p of the rotating anode 6. A cathodhaving two electron guns 9,10 are f - 4 disposed within the interior of the fluid tight metal casing I for emitting electron beams q,r indicated by broken lines such as thermoelectrons. Each electron gun 9,10 includes wehnelt cylinders 11,12 and coil filament 13,14, respectively.

Conductors 16A and 16B are connected to both ends of the coil filaments 13 and 14, and the coil filaments 13 and 14 are thereby floatingly supported. Free end terminals of those conductors 16 are taken externally out of the casing 1. And, the electron gun 9 is disposed so as to confront the peripheral surface 7a of truncated cone portion 7 with a predetermined spacing therebetween.

On the other hand, the electron gun 10 is disposed so as to confront the peripheral surface 8a of truncated cone portion 8 with a predetermined spacing therebetween.

Furthermore, as shown in Figs. I and 2 the casing I is provided with two windows 17,18 to allow X-rays to pass therethrough for taking out of Xrays in diametrically opposite positions with respect to the casing 1. Two windows 17,18 are positioned in confrontation with X-ray generating areas As,At on the truncated cone portions 7,8 to which areas As,At the electron beams emitted from the guns are directed for generating X-rays at the area. The line La passing through the center of two windows 17,18 is directed in parallel with the rotating axis p of the rotating anode 6. The line La, the rotating axis p and the center of two electron guns 9,10 are coplanar. The center of the window 17 positioned adjacent the X-ray generating area As 1 p 0 is positioned between the rotating axis p and an oblique line Lb which is an extension from the surface 8a and in the vicinity of the line Lb as shown in Fig 1. The center of the window 18 positioned adjacent the X-ray generating area At is positioned between the rotating axis p and an oblique line Lc which is an extension from the surface 7a and in the vicinity of Ahe line Lc. If necessary, an appropriate slit may be provided outside the window for taking out of only available X-rays.

With this arrangment,the windows 17 and 18 are provided so that the X-ray take off angle through each window is approximately 6 degrees with respect to the each face of the anode 6. Beryllium plate is available for those windows, since beryllium is excellent in X-ray transmission property. A tter(not shown) is provided to cover each of the windows for shut interrupting the X-ray from being leaked out when the X-ray is not used and is opened only when the X-ray is used.

Operation of the rotating anode X-ray tube thus constructed will be described below with reference to Fig. 1.

The motor is energized and the rotaing shaft 3 is rotated about its axis p through the endless belt 5. The rotaing anode 6 is rotated together with the rotation of the shaft 3. When a high voltage is applied to the electron guns 9,10, the coil filament 13,14 are heated and thermoelectrons are emitted therefrom. The thermoelectrons are accelerated to a high speed due to a high voltage difference between the electron gun 9,10 and the rotating anode 6, and impinge upon the X-ray generating 6 areas As,At. Two kinds of X-rays having different wavelength are generated from the X-ray generating areas As,At and are taken out of two respective windows 17,18 simultaneously, since the rotating anode 6 comprises two truncated cone portions 7,8 of 5which surfaces 7a,8a are made of diffrent materials such as copper and molybdenum. The X-ray take off angle through each window is approximately 6 degrees with respect to the each face of the anode 6.

With the above embodiment, as described above, the rotating loanode 6 is in the form of double truncated cones in which each of larger diameter areas is coupled together in order to provide substantially barrel like profile, and the peripheral surfaces 7a,8a of two truncated cone portions 7,8 are made of different materials different from each other such as copper and 15molybdenum. Therefore, the X-rays passing through the window 17 or the slit provided outside the rotating anode X-ray tube are limited to the X- rays generated from the X-ray generating area As, and the X-rays passing through the window 18 are also limited to the X-rays generated from the X- ray generating area 20At.

Next, an analyzer such as a diffractometer which employs the rotating anode X-ray tube according to the present invention will be described with reference to Fig. 3.

As shown in Fig. 3, the diffractometer includes the rotating 25anode X-ray tube T, X-ray detecting devices 20,21 comprising goniometer, scintillation counter, data processing unit or the I like. The X-ray detecting devices 20,21 are provided so as to confront windows 17,18, respectively. The X-rays are taken out of windows 17,18 in a direction perpendicular to longitudinal axis Ld of the rotating anode X- ray tube. That is, the X-ray detecting device 20 is disposed so that the X-rays taken out of the window 17 are incident upon interior of the device 20, while the X-ray detecting device 21 is disposed so that the X-rays taken out of the window 18 are incident upon interior of the device 21.

With this arrangement, in the X-ray detecting device 20 provided adjacent the window 17, characteristic X-rays on the basis of material of the surface 7a of the truncated cone portion 7 are incident upon a sample 22, and diffracted X-rays reflected therefrom are detected and processed by the l5goniometer, the sciintillation counter, the data processing unit or the like, to thereby perform an elementary analysis.

Further, if a Laue camera is employed in place of the diffractometer as the detecting device 20, the diffracted. X-rays passing through the sample 22 are directly recorded by The Laue 20camera, to thereby analyze a crystal structure.

In the same manner, in the X-ray detecting device 21 provided adjacent the window 18, another characteristic X-rays on the basis of material of the surface Ba of the truncated cone portion 8 are utilized, and the elementary analysis, the crystal 25structure analysis and some other analyses are performed.

As will be apparent from the aforementioned description, according to the present invention, two kinds of X-rays having wavelength characteristics different from each other can be simultaneouly taken out of two windows spacedly provided from each other. Further, the X-rays are taken out of windows in a direction perpendicular to longitudinal axis of the rotating anode X-ray tube. Accordingly, resultant analyzer which employs the rotating anode X- ray tube has a simple and compact structure.

1%,

Claims

CLAIMS i. A rotating anode X-ray tube for generating X-rays comprising:

a cas ing having at least two exit windows for the X-rays disposed opposite one another, the casing containing an interior space; an anode rotatable about an axis, within the interior space and formed of two truncated conical portions which provide generatrixes and peripheral surfaces, each of said generratrixes being inclined by a small angle in opposite directions with respect to the rotational axis, and the peripheral surfaces of the two portions being made of different materials; and, cathode means provided in confrontation with the anode for emitting two electron beams in different directions, the electron beams being incident upon their respective peripheral suraces, whereby the two kinds of X-rays generated at the two peripheral surfaces leave the 110 casing through their respective exit windows.
2. A rotating anode X-ray tube according to claim 1, wherein the casing is fluid tight and made of metal.
3. A rotating anode X-ray tube according to claim 1 or 2, wherein the anode has the form of double truncated cones in which the larger diameter areas of the two cones is coupled together to provide a substantially barrel-like profile.
4. A rotating anode X-ray tube according to any one of the preceding claims, wherein the peripheral surfaces of the two truncated cones are made of copper and molybdenum, respectively.
5. A rotating anode X-ray tube according to any one of the preceding claims, wherein the cathode means comprises two electron guns, each one of electron guns being in I 1 is confrontation with said respective truncated cone.
6. A rotating anode X- ray tube substantially as described with reference to the accompanying drawings.

its peripheral surfaces 01.

Publiahad 1989 at The PatentOffice. State House, 68,171 High HolbornIondonWCIR4TP. Further copies maybe obtaJmedfrom The Patentoffice. Sales Branch, St Mary Cray, Orpington. Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Oray, Kent, Con. 1/87 b