JPH083558B2 - X-ray spectrometer - Google Patents

Description

Detailed Description of the Invention a. TECHNICAL FIELD The present invention relates to an X-ray spectrometer using a curved crystal.

B. 2. Description of the Related Art In an X-ray spectroscope using a curved crystal, when a spectroscopic crystal is curved so that its lattice plane becomes a toroidal plane, X-rays emitted from one point on the Roland circle are converged on one point on the Roland circle. You can However, it is difficult to bend a solid in two directions orthogonal to each other, and conventionally, in an X-ray spectrometer using a curved crystal, a cylindrical curved crystal in which the crystal is curved in only one direction has been used as a spectroscopic element. When a dispersive crystal curved into a cylindrical surface is used, an X-ray emitted from a point S1 on the Rowland circle on one plane P orthogonal to the dispersive crystal C plane as shown in FIG. It can be converged to one point S2, but considering three-dimensionally,
The X-ray flux a emitted from the S1 point at a certain angle with the P-plane does not meet the diffraction conditions that are true for the X-rays on the P-plane, and the line l that is set up perpendicular to the P-plane at the S2 point. It will be converged with a certain aberration on the upper part, and if a slit is provided along the line 1, the X-ray convergence efficiency will decrease and the wavelength resolution will also decrease.

The above-mentioned problem is caused by bending the dispersive crystal in the plane P with a curvature whose radius is the direct system of the Rowland circle R in FIG.
The geometrical optics can be solved by curving a straight line connecting S1 and S2 in the direction perpendicular to the plane so that it becomes a plane of rotation about the axis of rotation. There are difficulties in one respect. One is that it is difficult to bend a solid crystal in two directions as described above, and the other is that the curvature in the direction orthogonal to the plane P of the dispersive crystal causes the wavelength scanning to change. With this, that is, as points S1 and S2 are moved on the Roland circle, they must be changed.

Because of the difficulty as described above, a dispersive crystal simply curved into a cylindrical surface has been mainly used conventionally. It is also proposed that the dispersive crystal curved into a cylindrical surface is cut into two or three pieces in parallel with the plane P of FIG. 5 and each cut piece is inclined to approximate one toroidal surface. However, since the crystal curvature in the direction orthogonal to the plane P is fixed to one, there is a problem that it has an effect only at a certain specific wavelength and is not suitable for scanning in a wide wavelength range.

C. DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, in the X-ray spectrometer using the curved crystal, the spectral crystal is curved to the toroidal surface in order to increase the X-ray focusing efficiency and improve the resolution. There is an attempt to solve the difficulty that the curvature must be changed with wavelength scanning.

D. Means for Solving Problems In an X-ray spectrometer having a curved crystal C as a spectroscopic element as shown in FIG. 1, the curved crystal C is formed into a line parallel to a reference plane P including a Rowland circle R passing through the center thereof. Multiple parts along
The dispersive crystal 2, which is divided into 1, 2 and 3 and intersects with the reference plane, is fixed to the substrate 7, and the dispersive crystals 1 and 3 which do not intersect with the reference plane are positioned in the direction perpendicular to the respective crystal surface centers and the reference plane. The inclination with respect to
The normal line which is erected at the center of each surface of the movable dispersive crystal by interposing the driving devices 6 and 6'with the movable dispersive crystal is always
The position and inclination of each movable dispersive crystal in the front-rear direction so as to pass through an intersection point 0 of a straight line connecting the X-ray incident point S1 and the convergent point S2 on the reference plane and a perpendicular line drawn from the center of the Rowland circle R to this straight line. A control means for controlling the is provided.

E. Operation As described above, in an X-ray spectroscope using a curved crystal, the dispersive crystal should ideally be curved in a toroidal plane, and the curvature in the plane orthogonal to the Rowland circle of the dispersive crystal should be interlocked with wavelength scanning. According to the present invention, the dispersive crystal is divided into a plurality of lines by a line parallel to the reference plane, and the center normal of each divided portion is controlled so as to intersect with the rotation axis of the toroidal plane. Because it will be
Good convergence can be obtained in the entire wavelength range of the spectroscope, and the resolution can be improved.

F. Embodiment FIG. 2 shows an essential part of an embodiment of the present invention. This figure shows a cross section perpendicular to the Rowland circle that passes through the center of curvature of the Rowland circle of the dispersive crystal. Reference numerals 1, 2, and 3 are dispersive crystals, which are obtained by dividing a crystal, which is curved into a cylindrical surface whose radius is the diameter of a Rowland circle, into three parts in a plane orthogonal to the cylindrical axis. A plane P that passes through the center of the central dispersive crystal 2 and includes a line y perpendicular to the crystal surface at that point and that is perpendicular to the plane of the drawing is the reference plane of the spectroscope. The radius of curvature of the dispersive crystal 2 in this reference plane is equal to the diameter of the Rowland circle, and the center of curvature is at point D on the y-axis. The 0 point on the y-axis is the y of the straight line connecting the incident point and the emission point of the X-ray located on the Rowland circle on the reference plane P of the spectrometer.
It is the intersection with the axis, and the ideal dispersive crystal is one that is curved centering on this 0 point along the arc r that is in contact with the surface of the dispersive crystal 2 at the center q.
In this embodiment, the dispersive crystal is divided into three pieces of 1, 2, and 3 so that each piece of crystal is in contact with the arc r. That is, the crystal 2 in the center is fixed to the substrate 7, and the crystals 1 and 3 on both sides are attached to the substrate 7 through the driving mechanisms 6 and 6 ', respectively, and the driving mechanisms 6 and 6'are determined by the wavelength scanning of the spectroscope. Following the movement of the 0 point on the y-axis, the crystals 1 and 3 are driven so that the perpendicular line standing at the surface center of each crystal 1 and 3 always passes through the 0 point.

FIG. 3 shows the whole of the above-described embodiment, S is a sample, e is an electron beam focused on a point S1 on the sample S, and the sample S is excited by this electron beam to generate S1.
X-rays are emitted from the points. The spectroscope is moved along a straight line L fixed to the apparatus, with the surface center q of the central crystal 2 of the dispersive crystals 1, 2, 3 passing through point S1. S2 is an X-ray emission slit, and G is an X-ray detector arranged integrally with S2. The plane including S1, q, S2 in the figure, that is, the plane of the figure is the reference plane P of the spectroscope, and S1, q, S2 are mechanically connected so that they are located on the Rowland circle R on this reference plane. There is. These connecting mechanisms are arbitrary and various types are already in practical use. In this embodiment, a substrate 7 holding the dispersive crystals 1 and 2.3 is attached to a nut (under the substrate 7 and not visible in the figure) screwed into a feed screw T arranged parallel to the straight line L. It is attached so that it can rotate around a vertical axis that passes through q,
A link l1 having one end at the projection point of S1 on a plane parallel to the reference plane P and having a length equal to the radius of the Rowland circle R and a link connected to l1 at one end Q and having a length Qq equal to l1. l2 is integrated with the substrate 7 so that the dispersive crystals 1, 2, and 3 are always directed to the center R of the Rowland circle. Further, a slit S2 is provided on the link l3 extending from the point q so as to be slidable in the longitudinal direction of the link, and the slit always faces the dispersive crystals 1, 2, and 3 and the links l1, l2 and the point Q. Is rotatably connected to a link l4 which has a length of QS2 equal to l1 and l2, and the position on the link l3 is controlled so that S1q = qS2.

The feed screw T is rotated by a stamping motor M operated by a drive pulse sent from the control circuit 10, whereby the dispersive crystals 1, 2 and 3 are moved along a straight line L to perform wavelength scanning. , Control circuit
Reference numeral 10 detects the wavelength of the dispersed X-ray emitted from the slit S2 to the detector G by counting the pulses sent to the stepping motor M. Further, the control circuit 10 controls the driving devices 6, 6'of the dispersive crystals 1, 3 according to the above-mentioned pulse count values.
Are in control.

Returning to FIG. 2, the drive devices 6, 6'will be described in detail. The dispersive crystals 1 and 3 are fixed to holding plates 5 and 5 '. Holding plate 5,
5'is respectively pivoted by a pin 11 common to a slider 9 slidable in the y-axis direction in a slide groove 8 parallel to the y-axis on the substrate 7, and 5'and 5 ' It is freely rotatable in the plane P. A spring 12 is interposed between the slider 9 and one end of the groove 8 so that the slider 9 is always pressed to the right in the figure.
A piezoelectric drive device 6 is interposed between the piezoelectric drive device 6 and the opposite end. Arms 51 and 51 'are extended rearward from the holding plates 5 and 5', and a tension spring 13 is stretched between the ends of the arms 51 and 51 'so that the arms 5 and 51' are extended.
1,51 'is always attracted. 6'is another piezoelectric drive device, which is interposed between the arms 51, 51 '.
Considering the case of performing wavelength scanning from the long wavelength side to the short wavelength side, the 0 point gradually approaches the q point in FIG. 2 and the radius of the arc r decreases. Along with this, the slider 9 moves to the right and the arms 51, 5
It needs to be spread during 1 '. That is, the drive device 6
Must be reduced in length and drive 6'can be extended in length. This reduction amount and extension amount are the driving devices 6, 6'at the long wavelength end position of the wavelength scanning range of the spectrometer.
Is determined as a function of wavelength with reference to the length of. The control device 10 calculates the above-mentioned reduction amount and extension amount based on the count value of the pulses sent to the stepping motor M, and sends the corresponding number of pulses to the driving devices 6 and 6'to control the respective lengths. To do. The links 14 and 14 are for allowing the holding plates 5 and 5'to move symmetrically.

FIG. 4 shows the construction of the drive devices 6, 6 '. The power part of this device is a device using a piezoelectric element called an inch worm, which includes three piezoelectric elements p1, p2, p3, and one pulse is sequentially added to these to perform one step movement, and the applied pulse The forward and backward movements are switched by changing the order, and the amount of movement of one step varies depending on the voltage applied to the piezoelectric element p2, and can be arbitrarily set within the range of 0.01 μm to 1 μm. Two back-to-back K-shaped pieces k1 and k2 are integrally bonded by sandwiching the piezoelectric element p2 and fitted in the guide groove V. Now, when voltage is applied to the piezoelectric element p1, the arm of the piece k1 is expanded.
k1 is clamped in the groove V. When a voltage is applied to p2 in this state, p2 extends and piece k2 is moved rightward by a step. When voltage is applied to p3 while voltage is applied to p1 and p2, the piece k2 is clamped in the groove V. Therefore, when the voltage applied to p1 and p2 is released, one side of k1 is pulled to the right and the entire one-step movement is completed. When moving the whole to the left, the order of voltage application may be reversed. Drive unit 6,
6'comprises a body B having a groove V formed therein and a rod b joined to the piece k1, and drives the crystals 1 and 3 by changing the length between the right end of the body B and the left end of the rod b. To do.

G. Effect The present invention is one in which a dispersive crystal is divided and approximated to an ideal toroidal surface, but the divided crystals are not fixed to each other, and the tilt with respect to the reference plane of the spectroscope is controlled, Since the curvature in the cross section perpendicular to the reference plane is always matched with the curvature of the ideal toroidal surface in conjunction with the wavelength scanning, the same high efficiency and resolution can be obtained in the entire measurement wavelength range of the spectrometer.

[Brief description of drawings]

FIG. 1 is a perspective view for explaining the outline of the present invention, FIG. 2 is a longitudinal sectional view of an essential part of an embodiment of the present invention, FIG. 3 is an overall view of the same embodiment, and FIG. 4 is for the same embodiment. FIG. 5 is a plan view of the driving device 6, 6 ', and FIG. 5 is a perspective view of a conventional example. S1 …… X-ray incident point on the spectrograph, S2 …… X-ray converging point on the spectrograph, C, 1,2,3 …… Dispersing crystal, R …… Roland circle, 5,5 ′
…… Holding plate, 6,6 ′ …… Drive device, 7 …… Substrate, 8 ……
Groove, 9 …… Slipper, 10 …… Control circuit, 11 …… Pin, 12 ……
Spring, 13 ... tension spring, G ... X-ray detector, e ... electron beam, S ... sample, V ... groove, k1, k2 ... piece, p1, p2, p
3 ... Piezoelectric element, B ... Driving device body, b ... Rod.

Claims (1)

[Claims] 1. An X-ray spectroscope having a curved crystal as a spectroscopic element, wherein the curved crystal is divided into a plurality of lines along a line parallel to a reference plane including a Rowland circle passing through the center, and each of the divided spectra. The crystal that intersects with the reference plane is fixed to the substrate, and the dispersive crystals that do not intersect are mounted on the substrate so that the position in the direction perpendicular to the center of each crystal surface and the inclination with respect to the reference plane are variably attached, and the crystal is movable with the substrate. A movable device is interposed between the dispersive crystal and the surface of the dispersive crystal so that the normal to the surface center of each dispersive crystal is always the same as the straight line connecting the incident point and the focusing point of the X-ray on the reference plane. An X-ray spectroscope in which means for controlling the driving device is provided so as to pass through an intersection with a perpendicular line drawn from the center of the circle to the straight line, and the substrate is driven by a wavelength scanning mechanism.