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Proceedings Paper

Laterally graded multilayer optics for x-ray analysis
Author(s): Manfred R. Schuster; H. Goebel; Lutz Bruegemann; D. Bahr; F. Burgaezy; Carsten Michaelsen; Michael Stoermer; P. Ricardo; Reiner Dietsch; Thomas Holz; Hermann Mai
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Paper Abstract

Periodic multilayers are well known as Bragg reflectors for X- rays. A high reflectivity and a wide reflection width are their outstanding features. However, if multilayers shall be used as reflective coating for X-ray optics, especially for wide acceptance angles, uniform layer thicknesses cause chromatic aberrations. These aberrations can be overcome by laterally graded multilayer optics. Their Bragg angle is matched laterally to the incidence angle so that for all points on the reflector, Bragg reflection is obtained for the same wavelength. Three major types of laterally graded multilayer mirrors ('Gobel Mirrors') are applied in X-ray diffractometry: (1) parabolic, (2) elliptic and (3) planar. In this paper, we give design criteria and formulae for these mirrors. Furthermore, we discuss the requirements on the dimensions and the fabrication process. Two different processes suitable for the fabrication, sputter coating and pulsed laser deposition (PLD), are described. The X-ray optical parameters and their characterization are presented for various mirrors designed for Cu K(alpha) , Mo K(alpha) and Cr K(alpha) radiation. From Ni/C and Ni/B4C multilayers, high-photon-flux monochromators with a Cu K(beta) /K(alpha) intensity ratio of about 1:1000 have been realized. The divergence of the 'parallel' beam reflected from parabolic mirrors is about 0.02 degrees, which is one order of magnitude lower than the divergence of polycapillary optics, monocapillary optics and waveguides. Comparing the photon flux density in a high resolution diffraction setup with and without mirror optics a gain factor of 16 was achieved for parabolic Ni/B4C multilayer mirrors.

Paper Details

Date Published: 23 November 1999
PDF: 16 pages
Proc. SPIE 3767, EUV, X-Ray, and Neutron Optics and Sources, (23 November 1999); doi: 10.1117/12.371116
Show Author Affiliations
Manfred R. Schuster, Siemens AG (Germany)
H. Goebel, Siemens AG (Germany)
Lutz Bruegemann, Bruker AXS GmbH (Germany)
D. Bahr, Bruker AXS GmbH (Germany)
F. Burgaezy, Bruker AXS GmbH (Germany)
Carsten Michaelsen, GKSS Research Ctr. (Germany)
Michael Stoermer, GKSS Research Ctr. (Germany)
P. Ricardo, GKSS Research Ctr. (Germany)
Reiner Dietsch, Fraunhofer Institute for Material and Beam Technology (Germany)
Thomas Holz, Fraunhofer Institute for Material and Beam Technology (Germany)
Hermann Mai, Fraunhofer Institute for Material and Beam Technology (Germany)

Published in SPIE Proceedings Vol. 3767:
EUV, X-Ray, and Neutron Optics and Sources
Carolyn A. MacDonald; Kenneth A. Goldberg; Juan R. Maldonado; Huaiyu Heather Chen-Mayer; Stephen P. Vernon, Editor(s)

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