X-ray diffractometer for mechanically correlated movement of the source, detector, and sample position
An X-ray diffractometer has a mechanism without toothed ring and is suited to move the two legs of a goniometer, on which the source and detector are respectively disposed, at the same time and in a correlated fashion. Each goniometer leg (or linkage) thereby has a common main center of rotation HDP and also one respective auxiliary center of rotation HD 1 , HD 2 . The two auxiliary centers of rotation are symmetrically disposed with respect to a symmetry plane E which contains the main center of rotation, and can be moved on a guidance that is symmetrical with respect to the plane E. The main center of rotation can only be moved in the plane E, e.g. along a rail guidance. The movement of the main center of rotation relative to the guidance can be easily driven by means of one single motor.
1. A diffractometer comprising:
a source for generating X-ray radiation;
means defining a sample position for disposition of a sample;
a detector for registration of X-ray radiation emitted by the sample, wherein said source and said detector can be rotated with respect to an axis A that extends through said sample position, said source, said sample position and said detector being disposed in a common plane M that is perpendicular to said axis A;
a first linkage disposed for rotation about said axis A and to which said source is mounted, said first linkage disposed at a first auxiliary center for rotation about a first auxiliary axis extending parallel to said axis A and at a fixed first separation therefrom;
a second linkage disposed for rotation about said axis A and to which said detector is mounted, said second linkage disposed on a second auxiliary center for rotation about a second auxiliary axis extending parallel to said axis A at said fixed first separation therefrom;
a guidance along which said first and/or said second auxiliary centers can be moved, said guidance extending mirror-symmetrically with respect to a plane E that contains said axis A and that has a same second separation from each of said first and said second auxiliary centers, wherein said sample position can be moved relative to said guidance in an x-direction extending in said plane E, perpendicularly to said axis A.
2. The diffractometer of claim 1 , wherein a separation between said source and said sample position is equal to a separation between said sample position and said detector.
3. The diffractometer of claim 1 , wherein said guidance extends in a straight line.
4. The diffractometer of claim 1 , wherein said first and said second auxiliary centers can be moved in opposite directions on said guidance.
5. The diffractometer of claim 1 , wherein said first auxiliary center, said source and said sample position define a first triangle in said common plane M and said second auxiliary center, said detector and said sample position define a second triangle in said common plane M.
6. The diffractometer of claim 5 , wherein said first triangle and said second triangle are equilateral triangles.
7. The diffractometer of claim 1 , further comprising a motor drive for moving said sample position relative to said guidance.
8. The diffractometer of claim 7 , wherein said guidance is stationary and said sample position can be moved along a stationary rail by means of said motor drive.
9. The diffractometer of claim 7 , wherein said guidance comprises a threaded rod that is driven by said motor drive.
10. The diffractometer of claim 7 , further comprising a control means for said motor drive, said control means advancing said sample position in said x-direction in accordance with a predetermined time function x(t).
11. The diffractometer of claim 10 , wherein said detector sweeps a same angular increment within a same time.
12. The diffractometer of claim 10 , wherein said control means advances said sample position in said x-direction in accordance with a predetermined time function x(t) with d/dt x(t)=const., and further comprising an evaluation means which takes into consideration a non-linear dependence Θ (x) for determining an intensity profile I(Θ) of the sample.
13. The diffractometer of claim 12 , wherein said control means corrects an intensity I(t i ) determined in a time interval t i through multiplication by a factor of
ⅆ
ϑ
ⅆ
x
❘
xi
,
wherein i is an index of integral individual measurements and x i an average x-value for an individual measurement i.
14. The diffractometer of claim 1 , wherein said detector is a one-dimensional detector with an elongated detector window, wherein said detector window lies in said common plane M over an entire length thereof.
15. The diffractometer of claim 1 , wherein said diffractometer is designed in such a fashion that a sample disposed at said sample position maintains an orientation thereof during relative motion of said sample position with respect to said guidance.
16. The diffractometer of claim 15 , wherein the sample is horizontal.
17. The diffractometer of claim 15 , wherein the sample is vertical.