In Fraunhoffer diffraction we use optical lens for focussing the diffracted light to meet at different points of maxima or minima. For X-RAY diffraction we don't.
ALSO FOR LASER DIFFRACTION WE DON'T USE LENS FOR FOCUSING THE DIFFRACTED LASER LIGHT. WHAT IS THE CAUSE BEHIND? SHALL WE GET EXTRA ACCURACY BY USING LENSING ?
Regards
Nityananda Das
Traditional focusing x-ray with lenses like in optical and IR spectral region impossible to use because RI in x-ray spectra equal forever ever 1, 000000..
Focussing of x-rays at the wavelengths used for x-ray diffraction is hardly to perform. Eugene already stated above that the refractive index of the x-rays is very close to 1. Its decrement from 1 is in the order of 10-6.
I have doubts whether the XRD accuracy will be increased via any lens because the primary angular distribution of the x-rays impinging onto the sample will be changed too. So the measured diffraction pattern will be changed too (at least a bit).
Dear Eugene, how do you calculate RI of a material w.r.t. X Ray ? Do you use Cauchy Formula ? Then I would like to say that Cauchy Formula ,I think, is not applicable through the entire range of EM waves .
Regards
Nityananda Das
You may calculate the index of refraction online, I can strongly recommend the centre of X-ray optics website, i.e. http://cxro.lbl.gov/, and there you may find
http://henke.lbl.gov/optical_constants/getdb2.html
where you get an interface for the materials of desire.
The basic functionality of an x-ray lense is explained here:
http://photon-science.desy.de/research/research_teams/fs_petra/overview/x_ray_optics/nanofocusing_lenses/index_eng.html
and here:
http://photon-science.desy.de/research/research_teams/fs_petra/overview/x_ray_optics/refractive_x_ray_lenses/index_eng.html
Good luck, Dirk
Respected Prof. Dirk
Thank you for your good reference and guide.
Regards
Nityananda Das
Dirk has given excellent references (thanks for them);
but in general focussing of x-rays via lenses or mirrors is accompanied by a huge loss of x-ray flux. If there is no need of focussing to small spot, as it is mostly the case for XRD, focussing makes no sense.
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