Goniometer in an x-ray diffraction device

A goniometer in an X-ray diffraction device comprises a sample table rotatably provided about a center axis of a sample for holding a sample, an X-ray source rotatably provided about the center axis of the sample for irrdiating first X-ray onto a sample, and an X-ray detector rotatably provided about the center axis of the sample for detecting second X-rays resulting from the irradiation of the first X-rays, the second X-rays being diffracted X-rays depending upon a sample. The sample table, the X-ray source an the X-ray detector are rotatable independently of one another, and a component to be fixed can be freely selected in accordance with a purpose of measurement and sample attachments employed. As such, various kinds of measuring methods are available to perform X-ray diffraction analysis by a single goniometer.

BACKGROUND OF THE INVENTION 
The present invention relates to a goniometer in an X-ray diffraction 
device, and more particularly to an improvement of a goniometer which is 
used in conjunction with an X-ray diffraction device, such as a 
diffractometer. 
An X-ray diffraction device, such as a diffractometer, has been used for 
X-ray diffraction analysis. In X-ray diffraction analysis by the 
diffractometer, a crystal structure of a substance, for example, is 
analyzed by irradiating an X-ray onto the substance and measuring a 
diffraction angle of the X-ray reflected from or passed through the 
substance. A goniometer is employed in conjunction with the diffractometer 
for measuring a diffraction angle of the X-ray. 
Next, a basic structure of a conventional goniometer will be described with 
reference to FIG. 12. 
The goniometer comprises an X-ray source 60, a receiving slit 61, X-ray 
detector 62, and a sample table for holding a sample 63. The X-ray source 
60 and the receiving slit 61 are disposed so that the distance L1 between 
the X-ray source 60 and the sample 63 is equal to the distance L2 between 
the receiving slit 61 and the sample 63. Therefore, the X-ray source 60 
and the receiving slit 61 are always positioned on a predetermined circle 
64 having a radius of L1 (=L2) which is drawn around a center axis 0 of 
the sample 63. The predetermined circle 64 is referred to as the 
diffractometer circle. The goniometer is classified into two types 
depending upon the plane in which its diffractometer circle is included, 
one of which is of a lateral type having the diffractometer circle in a 
horizontal plane, the other of which is of a vertical type having the 
diffractometer circle in a vertical plane. 
In the goniometer, in order to change an incident angle (.theta.) of the 
X-ray with respect to a lattice plane of a sample, it is necessary to 
change a relative position between the X-ray source 60 and the sample 63. 
In accordance with the change of the relative position therebetween, it is 
further necessary to change a relative position between the receiving slit 
61 and the sample 63 so that the diffracted X-ray is received in the 
receiving slit 61. Accordingly, in the conventional goniometer, two 
selected arbitarily from the X-ray source 60, the sample 63 and the 
receiving slit 61 are made to be rotatable about the center axis 0 of the 
sample 63 while unrotatably fixing the remainder. Depending upon the 
component unrotatably fixed, the goniometer is classified into three 
types; the X-ray source fixed type (referred to as .theta.-2.theta. 
operation system) in which the X-ray source is unrotatably fixed, the 
sample table fixed type (referred to as .theta.--.theta. operation system) 
and the receiving slit fixed type (or the X-ray detector fixed type). 
These three types of goniometers are applicable to both the lateral and 
vertical types of goniometers aforementioned. In general, employed are the 
X-ray source fixed and the lateral type goniometer, the X-ray source fixed 
end the vertical type goniometer, and the sample fixed and the vertical 
type goniometer. Particularly the sample horizontally fixed and the 
vertical type is referred to as a horizontal type goniometer. 
In the conventional goniometer, any one of the X-ray source, the sample and 
the X-ray detector disposed adjacent the receiving slit is unrotatably 
fixed. Selection of the component to be unrotatably fixed is determined on 
the basis of intended advantages. However, each of the three unrotatably 
fixed manners may inherently provide disadvantages. That is, the X-ray 
source fixed type has a disadvantage in that a heavy weight structure is 
not applicable to both the sample table and the X-ray detector because of 
necessity of their rotation. Therefore, attachments of heavy weight, such 
as high pressure vessel, cannot be provided on the sample table. Further, 
an X-ray detector of heavy weight, such as a solid state detector, cannot 
be utilized. On the other hand, in the X-ray source fixed type, a large 
scale X-ray source cannot be used because of the necessity of its 
rotation. 
SUMMARY OF THE INVENTION 
The present invention has been made in view of the foregoing disadvantages, 
and accordingly, it is an object of the present invention to provide a 
goniometer in which a sample table, an X-ray source and an X-ray detector 
are made to be rotatable independently of one another, such that the 
component to be fixed can be freely selected in accordance with a purpose 
of measurement and sample attachments attached to the components, such as 
a sample table. 
In order to achieve the foregoing and other objects, according to the 
present invention, there is provided a goniometer in an X-ray diffraction 
device for irradiating first X-rays onto a sample and detecting second 
X-rays resulting from the irradiation of the first X-rays, the second 
X-rays being diffracted depending upon a sample, and a sample having a 
center axis, the goniometer comprising: a sample table rotatably provided 
about the center axis of the sample for holding the sample; an X-ray 
source rotatably provided about the center axis of the sample for 
irradiating the first X-rays onto the sample; an X-ray detector rotatably 
provided about the center axis of the sample for detecting the second 
X-rays. According to the present invention, since the sample table, the 
X-ray source and the X-ray detector are rotatable independently of one 
another, a component to be fixed can be freely selected in accordance with 
a purpose of measurement and sample attachments employed, various kinds of 
measuring methods are available to perform X-ray diffraction analysis by a 
single goniometer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates a lateral type goniometer according to one embodiment of 
the invention. 
A goniometer comprises a base plate 10, a sample table unit 20, an X-ray 
detector unit 30 and an X-ray tube unit 40. The units 20 and 30 are 
assembled together through the bearings 34, 35 interposed therebetween, 
end the units 30 and 40 are assembled together through the bearings 44, 
45. The base plate is integral with a cylindrical member 11. The 
cylindrical member 11 has a large-diameter portion and a small-diameter 
portion, and an open end of the former is integral with the base plate 10. 
The interior of the cylindrical member 11 defines a space 12 for 
accommodating a shaft 22 and a wormwheel 23. 
The sample table unit 20 includes a sample table 21 for holding a sample, 
the shaft 22 extending vertically and supported by the cylindrical member 
11 through bearings 24, 25, and the wormwheel 23 fixedly secured to the 
lower end of the shaft 22 and accommodated within the space 12. A spacer 
26 is interposed between the two bearings 24,25. A sample plate 27 is 
detachably mounted on the sample table 21. The wormwheel 23 is in meshing 
engagement with wormgear 28 connected to a pulse motor 29 as shown in FIG. 
2. 
The X-ray detector unit 30 includes a hollow shaft 31 extending vertically 
and supported by the cylindrical member 11 through bearings 34,35, a 
supporting arm 32 horizontally extending and mounted on the upper end of 
the hollow shaft 31 end a wormwheel 33 fixedly secured to the lower end of 
the shaft 31. A spacer 36 is interposed between two bearings 34,35. An 
X-ray detector 37 is mounted on the supporting arm 32. A receiving slit 51 
and a scatter slit 52 are disposed adjacent the X-ray detector 37 on the 
supporting arm 32. The wormwheel 33 is in meshing engagement with a 
wormgear 38 connected to a pulse motor (not shown) in the same manner as 
shown in FIG. 2. 
The X-ray tube unit 40 includes a hollow shaft 41 extending vertically and 
supported by the hollow shaft 31 through bearings 44, 45, a supporting arm 
42 integrally provided on the upper end of the hollow shaft 41, and a 
wormwheel 43 fixedly secured to the lower end of the shaft 41. A spacer 46 
is interposed between two bearings 44,45. An X-ray tube 47 is slidably 
movable provided on the supporting arm 42. That is, the supporting arm 42 
is formed with a groove 42a extending in a direction perpendicular to the 
sheet of drawing, the X-ray tube 47 has a lower end portion 47a engaged 
with the groove 42a. Therefore, the X-ray tube 47 is moved along the 
longitudinal direction of the groove 42a by the activation of a pulse 
motor (not shown). A divergence slit 53 is disposed adjacent the X-ray 
tube 47 on the supporting arm 42. The wormwheel 43 is in meshing 
engagement with a wormgear 49 connected to a pulse motor (not shown) in 
the same manner as shown in FIG. 2. 
With this arrangement, X-rays generated from the X-ray tube 47 pass through 
the divergence slit 53 which limits their divergence. The X-rays are 
incident upon a sample on the sample table 27, diffracted X-rays reflected 
therefrom are detected and processed by the X-ray detector 37 after 
passing through the receiving slit 51 and the scatter slit 52. The 
receiving slit 81 serves to limit the X-rays entering the X-ray detector 
37, the scatter slit 52 serves to interrupt and prevent the scattering 
X-rays from entering the X-rays detector 37. Only the X-ray from the 
sample are allowed to enter the X-ray detector 37. In this X-ray 
diffraction analysis, when the wormgears 38 and 49 are driven, the X-ray 
tube 47 provided on the hollow shaft 41 and the receiving slit 51 provided 
on the hollow shaft 31 are independently rotated about the center axis 15 
of the sample on the diffractometer circle. The X-ray detector 37 is 
rotated about the center axis 15 of the sample together with the receiving 
slit 51. The sample table 27 is further independently rotatable about the 
center axis 15 by driving the wormgear 28. That is, the sample table 21, 
X-ray detector 37 and X-ray tube 47 are rotatable about the center axis 15 
in the goniometer independently of one another. 
Next, several methods of using the goniometer thus constructed will be 
described below with reference to FIGS. 3 through 9. 
FIGS. 3 through 9 are plan views showing the relationship of relative 
position among X-rays 54 generated from the X-ray tube 47, the sample 55 
on the sample table and the X-ray detector 37, any other components are 
not shown. These figures illustrate the lateral type goniometer, in case 
of the vertical type goniometer, FIGS. 3 through 9 can be seen as front 
views in place of plan views. In FIGS. 3 through 9, .theta.s represents a 
rotational angle of the X-ray tube 47, .theta.c a rotational angle of the 
sample table 21, and .theta.d a rotational angle of the X-ray detector 37. 
A. In case of the X-ray tube fixed: 
The X-ray tube, namely, the X-rays 54 is fixed, and thus the rotational 
angle .theta.s of the X-ray tube is unchangeable. In this case, an angular 
velocity of the X-ray detector 37 is set to be twice as large as that of 
the sample 55, that is, when the rotational angle .theta.c of the sample 
table is .theta., the rotational angle .theta.d of the X-ray detector 
becomes equal to 2.theta. as shown in FIG. 3. This arrangement of the 
goniometer is same as that of the conventional lateral goniometer. 
B. In case of the sample table fixed: 
The sample table is fixed, and thus the rotational angle of the sample is 
unchangeable. The reference numeral 56 designates a normal line of the 
lattice plane to be measured. In this case, an angular velocity of the 
X-ray tube 47 is set to be equal to that of the X-ray detector 37, that 
is, when the rotational angle .theta.s of the X-ray tube is .theta., the 
rotational angle .theta.d of the X-ray detector becomes equal to .theta. 
as shown in FIG. 4. Since this arrangement of the goniometer includes the 
sample table fixed, attachments of heavy weight, such as high pressure 
vessel, can be provided on the sample table. The sample can be held 
horizontally, if this arrangement is applied to the vertical type 
goniometer. 
FIG. 5 shows another method of using the sample table fixed type 
goniometer. In this method the lattice plane to be measured is inclined 
with respect to a surface of the sample 55. Strain in the sample 55 may be 
observed and measured by performing X-ray diffraction analysis in a state 
in which inclination degree of the sample 55 is changed. That is, when the 
sample 55 is subject to external load, such as a tensile load, a lattice 
plane interval becomes longer or shorter depending on directions, for 
example, in case the tensile load is applied to the sample 55, there 
exists not only an axial strain which causes elongation in the tensile 
direction, but also a lateral strain which causes shrinkage in a direction 
perpendicular to the tensile load. The strain in a direction selected 
arbitarily among these strains may be measured by the method as shown in 
FIG. 5. 
FIG. 6 shows still another method of using the sample table fixed type 
goniometer. In this method, the lattice plane to be measured is also 
inclined with respect to a surface of the sample 55. Only one difference 
between the methods shown in FIGS. 5 and 6 is that the sample is fixed 
without inclination. 
C. In case of the X-ray detector fixed: 
In this case, the X-ray detector is fixed, and thus the rotational angle of 
the X-ray detector is unchangeable. An angular velocity of the X-ray tube 
47 is set to be twice as large as that of the sample table 27, that is, 
when the rotational angle .theta.c of the sample table is .theta., the 
rotational angle .theta.s of the X-ray tube becomes equal to 2.theta. as 
shown in FIG. 7. Since this arrangement of the goniometer includes the 
X-ray detector 37 fixed, the X-ray detector 37 of heavy weight, such as a 
solid state detector, can be utilized. 
FIG. 8 shows another method of using X-ray detector fixed type goniometer. 
In this method, when the rotational angle .theta.s of the X-ray tube is 
equal to 2.theta., the rotational angle .theta.c of the sample table 
becomes equal to .theta.s-.alpha.. Accordingly, the X-rays 54 are incident 
upon the sample 55 at an angle .alpha. with respect to the surface of the 
sample. This method is employed to perform X-ray diffraction analysis for 
a film-like sample, since small incident angle allows X-rays to travel for 
a long distance in the film-like sample. The incident angle is usually 
adjusted to be in the range of 2 to 5 degrees. 
D. In case of the X-ray tube fixed and the sample table fixed: 
In this case, both the X-ray tube and the sample table are fixed, and thus 
the rotational angle .theta.s of the X-ray tube and the rotational angle 
.theta.c of the sample are set to be unchanged as shown in FIG. 9. This 
method is also applicable to measure film-like sample similar to the 
method shown in FIG. 8. The X-rays 54 and the sample 55 are fixed so that 
the X-rays 54 are incident upon the sample 55 at an angle .alpha. with 
respect to the surface of the sample. And the X-ray detector 37 is 
rotatable about the center axis of the sample 55. 
As will be apparent from the aforementioned description, according to this 
goniometer, various measuring methods are available to samples, a 
measuring method can be freely selected in accordance with a purpose of 
measurement and sample attachments employed. 
Next, the goniometer is interchangeably used either as a lateral type or a 
vertical type, which will be described with reference to FIGS. 10 and 11. 
In FIG. 10, a base plate unit 14 comprises a base plate 10 and a side plate 
13 vertically extending and fixedly provided on the base plate 10 with a 
hinge 16. The base plate 10 and the side plate 13 have two legs 17,17 at 
positions apart from the hinge 16, respectively. 
The goniometer G is shown by phantom lines on account of simplicity of 
drawings. The lateral type goniometer as shown in FIG. 10 can be used as 
the vertical type goniometer as shown in FIG. 11. That is, the base plate 
unit 14 is rotated by 90 degrees as indicated by an arrow 19, to thereby 
locate the base plate 10 holding the goniometer G vertically. With reverse 
rotation, the vertical type goniometer can be used as the lateral type 
goniometer. 
In view of the foregoing, according to the present invention, since a 
sample table, an X-ray source and an X-ray detector are independently 
rotatably provided, a component to be fixed can be freely selected in 
accordance with a purpose of measurement and sample attachments employed. 
Various kinds of measuring methods are thus available to perform X-ray 
diffraction analysis by a single goniometer. If, for example, the X-ray 
source and the X-ray detector are rotatable and the sample table is fixed, 
attachments of heavy weight, such as high pressure vessel, can be provided 
on the sample table. If both the sample table and the X-ray source are set 
to be rotatable while fixing the X-ray detector, the X-ray detector of 
heavy weight, such as a solid state detector, can be utilized. 
Further, according to the present invention. a lateral type goniometer and 
a vertical type goniometer are interchangeably used with a single 
goniometer, since position of a support member holding the goniometer is 
interchangeable between a vertical position and a horizontal position.