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Title: Graded Multilayers For Synchrotron Optics

Abstract

I will give a comprehensive overview on the use of multilayers as optical elements on 3rd generation synchrotron sources, in particular at the ESRF. In most reflecting multilayer optics, a synchrotron beam hits the optical surface under varying incident angles along the footprint of the element. Therefore, the multilayer period generally requires a lateral thickness gradient to keep the Bragg condition fulfilled over the full length of the optics. This gradient can be considerable, is typically non-linear, and has to be realized with a precision better than the width of the Bragg reflection. In particular cases, additional depth gradients or non-periodic structures may be applied. I will discuss the basic design ideas, the fabrication scheme, and the principal applications of graded multilayers at ESRF beamlines. A central part will deal with focusing devices based on the Kirkpatrick-Baez technology and their performance.

Authors:
 [1]
  1. European Synchrotron Radiation Facility, BP 220, F-38043, Grenoble Cedex (France)
Publication Date:
OSTI Identifier:
21052629
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 879; Journal Issue: 1; Conference: 9. international conference on synchrotron radiation instrumentation, Daegu (Korea, Republic of), 28 May - 2 Jun 2006; Other Information: DOI: 10.1063/1.2436173; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ACCURACY; BEAM OPTICS; BEAM PRODUCTION; BRAGG REFLECTION; DESIGN; EUROPEAN SYNCHROTRON RADIATION FACILITY; FOCUSING; LAYERS; NONLINEAR PROBLEMS; PERFORMANCE; PERIODICITY; PHOTON BEAMS; SYNCHROTRON RADIATION; X RADIATION

Citation Formats

Morawe, Christian. Graded Multilayers For Synchrotron Optics. United States: N. p., 2007. Web. doi:10.1063/1.2436173.
Morawe, Christian. Graded Multilayers For Synchrotron Optics. United States. doi:10.1063/1.2436173.
Morawe, Christian. Fri . "Graded Multilayers For Synchrotron Optics". United States. doi:10.1063/1.2436173.
@article{osti_21052629,
title = {Graded Multilayers For Synchrotron Optics},
author = {Morawe, Christian},
abstractNote = {I will give a comprehensive overview on the use of multilayers as optical elements on 3rd generation synchrotron sources, in particular at the ESRF. In most reflecting multilayer optics, a synchrotron beam hits the optical surface under varying incident angles along the footprint of the element. Therefore, the multilayer period generally requires a lateral thickness gradient to keep the Bragg condition fulfilled over the full length of the optics. This gradient can be considerable, is typically non-linear, and has to be realized with a precision better than the width of the Bragg reflection. In particular cases, additional depth gradients or non-periodic structures may be applied. I will discuss the basic design ideas, the fabrication scheme, and the principal applications of graded multilayers at ESRF beamlines. A central part will deal with focusing devices based on the Kirkpatrick-Baez technology and their performance.},
doi = {10.1063/1.2436173},
journal = {AIP Conference Proceedings},
number = 1,
volume = 879,
place = {United States},
year = {Fri Jan 19 00:00:00 EST 2007},
month = {Fri Jan 19 00:00:00 EST 2007}
}
  • We describe the development of depth-graded W/Si multilayer films prepared by magnetron sputtering for use as broad-band reflective coatings for hard x-ray optics. We have used specular and nonspecular x-ray reflectance analysis to characterize the interface imperfections in both periodic and depth-graded W/Si multilayer structures, and high-resolution transmission electron microscopy (TEM) and selected area electron diffraction (SAED) to characterize the interface structure and layer morphology as a function of depth in an optimized depth-graded multilayer. >From x-ray analysis we find interface widths in the range {sigma}=0.275-0.35 nm for films deposited at low argon pressure (with a slight increase in interfacemore » width for multilayers having periods greater than {approx}20 nm, possibly due to the transition from amorphous to polycrystalline metal layers identified by TEM and SAED), and somewhat larger interface widths (i.e., {sigma}=0.35-0.4 nm) for structures grown at higher Ar pressures, higher background pressures, or with larger target-to-substrate distances. We find no variation in interface widths with magnetron power. Nonspecular x-ray reflectance analysis and TEM suggest that the dominant interface imperfection in these films is interfacial diffuseness; interfacial roughness is minimal ({sigma}{sub r}{approx}0.175 nm) in structures prepared under optimal conditions, but can increase under conditions in which the beneficial effects of energetic bombardment during growth are compromised. X-ray reflectance analysis was also used to measure the variation in the W and Si deposition rates with bilayer thickness: we find that the W and Si layer thicknesses are nonlinear with the deposition times, and we discuss possible mechanisms responsible for this nonlinearity. Finally, hard x-ray reflectance measurements made with synchrotron radiation were used to quantify the performance of optimized depth-graded W/Si structures over the photon energy range from 18 to 212 keV. We find good agreement between the synchrotron measurements and calculations made using either 0.3 nm interface widths, or with a depth-graded distribution of interface widths in the range {sigma}=0.275-0.35 nm (as suggested by 8 keV x-ray and TEM analyses) for a structure containing 150 bilayers, and designed for high reflectance over the range 20 keV<E<70 keV. We also find for this structure good agreement between reflectance measurements and calculations made for energies up to 170 keV, as well as for another graded W/Si structure containing 800 bilayers, designed for use above 100 keV, where the peak reflectance was measured at E=212 keV to be R=76.5{+-}4% at a graze angle of {theta}=0.08 degree sign . (c) 2000 American Institute of Physics.« less
  • The temperature stability of metal (W, WRe, Co, Cr)-carbon multilayers has been studied using x-ray diffraction (theta--2theta and Debye--Scherrer) and electron microscopy. The results show that in all cases a crystallization occurs in the temperature range 650--750 /sup 0/C. As a consequence of this crystallization, the layered structure is destroyed, the surface of the film becomes rough, and the x-ray reflectivity is considerably reduced. These results imply that efficient cooling or new multilayer structures will have to be developed for use at high temperatures or under high x-ray incident flux.
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