dorsal/arxiv
View SchemaUnderstanding transverse coherence properties of X-ray beams in third generation Synchrotron Radiation sources
| Authors | Gianluca Geloni, Evgeni Saldin, Evgeni Schneidmiller, Mikhail Yurkov |
|---|---|
| Categories | |
| ArXiv ID | physics/0506231 |
| URL | https://arxiv.org/abs/physics/0506231 |
Abstract
This paper describes a theory of transverse coherence properties of Undulator Radiation. Our study is of very practical relevance, because it yields specific predictions of Undulator Radiation cross-spectral density in various parts of the beamline. On the contrary, usual estimations of coherence properties assume that the undulator source is quasi-homogeneous, like thermal sources, and rely on the application of van Cittert-Zernike (VCZ) theorem, in its original or generalized form, for calculating transverse coherence length in the far-field approximation. The VCZ theorem is derived in the frame of Statistical Optics using a number of restrictive assumptions: in particular, the quasi-homogeneous assumption is demonstrated to be inaccurate in many practical situations regarding undulator sources. We propose a technique to calculate the cross-spectral density from undulator sources in the most general case. Also, we find the region of applicability of the quasi-homogeneous model and we present an analytical expression for the cross-spectral density which is valid up to the exit of the undulator. For the case of more general undulator sources, simple formulas for the transverse coherence length, interpolated from numerical calculations and suitable for beamline design applications are found. Finally, using a simple vertical slit, we show how transverse coherence properties of an X-ray beam can be manipulated to obtain a larger coherent spot-size on a sample. This invention was devised almost entirely on the basis of theoretical ideas developed throughout this paper.
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"abstract": "This paper describes a theory of transverse coherence properties of Undulator\nRadiation. Our study is of very practical relevance, because it yields specific\npredictions of Undulator Radiation cross-spectral density in various parts of\nthe beamline. On the contrary, usual estimations of coherence properties assume\nthat the undulator source is quasi-homogeneous, like thermal sources, and rely\non the application of van Cittert-Zernike (VCZ) theorem, in its original or\ngeneralized form, for calculating transverse coherence length in the far-field\napproximation. The VCZ theorem is derived in the frame of Statistical Optics\nusing a number of restrictive assumptions: in particular, the quasi-homogeneous\nassumption is demonstrated to be inaccurate in many practical situations\nregarding undulator sources. We propose a technique to calculate the\ncross-spectral density from undulator sources in the most general case. Also,\nwe find the region of applicability of the quasi-homogeneous model and we\npresent an analytical expression for the cross-spectral density which is valid\nup to the exit of the undulator. For the case of more general undulator\nsources, simple formulas for the transverse coherence length, interpolated from\nnumerical calculations and suitable for beamline design applications are found.\nFinally, using a simple vertical slit, we show how transverse coherence\nproperties of an X-ray beam can be manipulated to obtain a larger coherent\nspot-size on a sample. This invention was devised almost entirely on the basis\nof theoretical ideas developed throughout this paper.",
"arxiv_id": "physics/0506231",
"authors": [
"Gianluca Geloni",
"Evgeni Saldin",
"Evgeni Schneidmiller",
"Mikhail Yurkov"
],
"categories": [
"physics.optics",
"physics.acc-ph"
],
"title": "Understanding transverse coherence properties of X-ray beams in third generation Synchrotron Radiation sources",
"url": "https://arxiv.org/abs/physics/0506231"
},
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