High resolution X-ray diffraction method and apparatus
An X-ray diffraction apparatus for high resolution measurement combines the use of an X-ray source with a target having an atomic number Z less 50 with an energy resolving X-ray detector having an array of pixels and a beta radiation multilayer mirror for selecting the K-beta radiation from the X-ray source and for reflecting the K-beta radiation onto the sample where it is diffracted onto the energy resolving X-ray detector. The sample may in particular be in transmission. The sample may be a powder sample in a capillary.
1. An X-ray diffraction apparatus, comprising:
an X-ray source with a target having an atomic number Z less than 50 for emitting a beam of X-rays;
an energy resolving X-ray detector, wherein the energy resolution of the X-ray detector is sufficient to select for K-beta radiation over K-alpha radiation with a sensitivity to K-beta radiation of at least 10 times the sensitivity to K-alpha radiation; and
a sample holder for holding a sample such that the beam of X-rays from the X-ray source are incident on the sample and are diffracted onto the X-ray detector;
wherein the X-ray diffraction apparatus further comprises a K-beta radiation multilayer mirror for selecting the K-beta radiation from the X-ray source and for reflecting the K-beta radiation onto the sample.
2. The X-ray diffraction apparatus according to claim 1 , wherein the sample holder is adapted to hold the sample in a transmission geometry such that the beam of X-rays from the X-ray source passes through the sample and is diffracted onto the X-ray detector.
3. The X-ray diffraction apparatus according to claim 1 , wherein the sample holder is adapted to hold, as the sample, a capillary holding a powder.
4. The X-ray diffraction apparatus according to claim 1 , wherein the K-beta radiation multilayer mirror is a focussing multilayer mirror arranged to focus the diffracted beam onto the energy resolving X-ray detector.
5. The X-ray diffraction apparatus according to claim 1 , wherein the combination of the K-beta radiation multilayer mirror and energy resolving X-ray detector is sufficient to attenuate the measured intensity of K-alpha radiation with respect to K-beta radiation by at least 1000 times.
6. The X-ray diffraction apparatus according to claim 5 , wherein each of the K-beta radiation multilayer mirror and energy resolving X-ray detector is sufficient to attenuate the measured intensity of K-alpha radiation with respect to K-beta radiation by at least 5 times.
7. The X-ray diffraction apparatus according to claim 1 , wherein the only components in the beam path after the K-beta radiation multilayer mirror are the sample in the sample holder and the energy resolving X-ray detector.
8. The X-ray diffraction apparatus according to claim 1 , wherein the multilayer K-beta radiation mirror is the only monochromator.
9. The X-ray diffraction apparatus according to claim 1 , wherein the X-ray detector has a linear array of pixels.
10. The X-ray diffraction apparatus according to claim 1 , wherein the target has an atomic number Z less than 30.
11. A method of X-ray diffraction, comprising:
a. generating a beam of X-rays from an X-ray source with a target having an atomic number Z less than 50;
b. directing the beam of X-rays onto a K-beta radiation multilayer mirror to select the K-beta radiation from the X-ray source and to reflect the K-beta radiation onto the sample;
c. directing the K-beta X-rays onto a sample such that the X-rays are diffracted by the sample; and
d. measuring the diffracted X-rays using an energy resolving X-ray detector, and selecting for K-beta radiation over K-alpha radiation by the energy resolving X-ray detector, wherein the energy resolving X-ray detector has a sensitivity to K-beta radiation of at least 10 times the sensitivity to K-alpha radiation.
12. The method of X-ray diffraction according to claim 11 , wherein the sample is held in a transmission geometry such that the beam of X-rays from the X-ray source passes through the sample and is diffracted onto the X-ray detector.
13. The method of X-ray diffraction according to claim 11 , wherein the sample is a capillary holding a powder.
14. The method of X-ray diffraction according to claim 11 , wherein the K-beta radiation multilayer mirror is a focussing multilayer mirror, the step of directing the beam of X-rays comprising focussing the beam of X-rays so that the diffracted beam is focussed on the energy resolving X-ray detector.
15. The method of X-ray diffraction according to claim 11 , wherein the combination of the K-beta radiation multilayer mirror and energy resolving X-ray detector is sufficient to attenuate the measured intensity of K-alpha radiation with respect to K-beta radiation by at least 1000 times.
16. The method of X-ray diffraction according to claim 11 , wherein the only components in the beam path after the K-beta radiation multilayer mirror are the sample in the sample holder and the energy resolving X-ray detector.
17. The method of X-ray diffraction according to claim 11 , wherein the X-ray detector has an array of pixels.
18. The method of X-ray diffraction according to claim 11 wherein the sample is a powder sample.