X-ray or gamma ray systems or devices – Beam control – Collimator
Reexamination Certificate
1999-10-27
2001-07-24
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Beam control
Collimator
C378S145000, C378S147000
Reexamination Certificate
active
06266392
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a soller slit used in an X-ray device, etc., for collimating diverging X-rays to parallel X-rays and a manufacturing method of the same soller slit.
2. Description of the Related Art
In general, a soller slit is constructed by piling up a plurality of thin metal foils with interposing a spacer therebetween and is used in an X-ray optical system to restrict vertical and/or horizontal divergence of X-rays. The metal foils of the conventional soller slit may be formed from rolled stainless steal or brass (Cu-Zn) and the like.
However, since such rolled metal foil has a mirror-surfaces, incident X-rays R
1
are totally reflected thereby as shown in
FIG. 7
, so that it is impossible to obtain parallel X-ray beams having required precision to thereby obtain an aimed resolution in an X-ray measurement. Particularly, in a case where the aimed resolution is not more than the critical angle for wavelength of incident X-rays at which total reflection occur, a divergence of X-rays due to total reflection becomes substantially equal to or more than the resolution, causing a big problem.
In order to restrict the total reflection, it has been usual, for example, to rough the surfaces of the metal foils by emery papers, to etch them with using acid, and to plate them. However, in any of the conventional roughing techniques, satisfactory high precision parallel X-ray beams, and thus, high resolution has not been obtained.
SUMMARY OF THE INVENTION
The present invention was made in view of the above mentioned state of art and has an object to provide a soller slit capable of forming parallel X-ray beams with high precision and improving resolution in an X-ray measurement.
According to the present invention, the above object can be achieved by a soller slit that is featured by the following matters:
(1) A soller slit comprising a plurality of metal foils stacked with a constant interval between adjacent foils and having a function to restrict divergence of X-rays when arranged on an X-ray optical path, is featured by that each metal foil is formed by sintering a metal material such that surfaces of the metal foil have high harmonic surface roughness.
In this specification, the term “high harmonic surface roughness” means the roughness of surface having a repetition of irregularity at short period, like high frequency vibration. In detail, the surface of the metal foil is smoother than a surface having a repetition of irregularity at long period like a surface roughed by emery finishing, by etching with acid etc., and is rougher than a super smooth surface such as a glass surface. In more detail, it is the surface roughness enough to prevent total reflection of X-rays from occurring.
The term “sintering” has the usual meaning. That is, a metal foil prepared by sintering a material can reliably provide high harmonic surface roughness within the required roughness range. The sintering is a still developing technology and it has been known that the surface roughness of a metal foil prepared by sintering a metal material with using the conventional sintering technology is considerable and it is difficult to provide the high harmonic surface required in the present invention. Recently, however, it becomes possible to provide such surface roughness as required in the present invention, by the sintering technology.
In view of the recent development of the sintering technology, it may be possible to form an ultra smooth surface condition close to a mirror surface having space period not larger than several tens &mgr;m and root mean square (RMS) value not larger than several tens nm(nanometer) by a sintering processing. In such case, however, a resultant ultra smooth surface might be outside the high harmonic surface condition required in the present invention.
In the soller slit according to the present invention, it is possible to prevent X-rays incident to the soller slit from being totally reflected on metal foils since metal foils have a high harmonic surface roughness. Thus, high precise parallel X-ray beams can be obtained, to thereby improve resolution in the X-ray measurement.
(2) Surface roughness of the metal foil and the like can be generally defined by the space period of X-rays and the RMS value (that is, mean amplitude of X-rays). A relatively rough surface obtainable by emery finishing and the like usually has a surface roughness defined by space period of 0.~1 mm and by RMS value of 0.1~1 &mgr;m. Also, an ultra smooth surface of a product such as a silicon substrate or a plate glass usually have a roughness defined by space period not larger than 25 &mgr;m and by RMS value of about 0.2 nm.
The high harmonic surface roughness in the present invention corresponds to surface roughness having space period of, for example not larger than 50 &mgr;m, preferably 20~50 &mgr;m and RMS value of, for example 20 nm~1 &mgr;m, preferably 20~50 nm, with which total reflection of X-rays can be prevented. Particularly, in order to obtain the effect expected in the present invention, it is considered as necessary to set RMS value within the above mentioned range.
(3) In the above-mentioned construction, the material forming the metal foil is not limited to any specific material. However, it may be preferably tungsten or molybdenum and the like.
(4) Another soller slit according to the present invention, which includes a plurality of metal foils stacked with a constant interval between adjacent foils and functions to restrict divergence of X-rays when the soller slit is arranged on an X-ray optical path, is featured by that each metal foil has oxide material formed on surface thereof by an oxidation processing and having high harmonic surface roughness.
Since the metal foils of the soller slit have high harmonic surface roughness, it is possible to restrict total reflection of X-rays incident on the soller slit, so that it becomes possible to form high precision parallel X-ray beams, to thereby improve resolution in the X-ray measurement.
Further, since the compound that is lighter in mass than the metal foil exists on the surfaces of the metal foil, another effect of reducing the critical angle for total reflection can be obtained.
Incidentally, the term “oxidation processing” means a processing for forming oxides on the surfaces of the metal foil, which is different from the etching processing for etching the surfaces of the metal foil. Etching processing cannot produce high harmonic surface roughness required in the present invention.
(5) In the construction of the soller slit mentioned in the paragraph (4), high harmonic surface roughness preferably has RMS value of 20 nm~1 &mgr;m, more preferably 20 nm~50 nm.
(6) In the construction of the soller slit mentioned in the paragraph (4), the material of the metal foil is not limited to any specific metal. For example, it may be brass or stainless steal, etc. In a case where brass is used as the material of the metal foil, using dense nitric acid or permanganate and the like can perform the oxidation processing. Also, in a case of employing a stainless steal, the oxidation processing using nitric acid may be difficult, since an oxide layer is formed on the surface of the metal foil and prevents further oxidation from occurring.
(7) A first method according to the present invention for manufacturing a soller slit including a plurality of metal foils stacked with a constant interval between adjacent ones of the metal foils, said soller slit being arranged on an X-ray optical path to restrict divergence of X-rays, wherein the metal foils are prepared by sintering a metal material such that surfaces thereof have high harmonic surface roughness.
According to this method, it is possible to collimate diverging X-rays to high precision parallel X-ray beams by preventing X-rays incident on the surfaces from being reflected totally to thereby improve resolution in the X-ray measurement.
(8) A second method according to the present invention for manufacturing a soller slit including
Fujinawa Go
Umegaki Shiro
Burns Doane , Swecker, Mathis LLP
Ho Allen C.
Kim Robert H.
Rigaku Corporation
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