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Development of Grazing Incidence Multilayer Mirrors for Hard X-ray Focusing Telescopes

Mao, Peter H. and Harrison, Fiona A. and Platonov, Y.Y. and Broadway, D. and DeGroot, B. and Christensen, F. E. and Craig, William W. and Hailey, C. J. (1997) Development of Grazing Incidence Multilayer Mirrors for Hard X-ray Focusing Telescopes. In: Proceedings of SPIE. Vol.3114. Society of Photo-Optical Instrumentation Engineers (SPIE) , Bellingham, WA, pp. 526-534.

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We are developing depth-graded, multilayer-coated mirrors for astrophysical hard X-ray focusing telescopes. In this paper, we discuss the primary technical challenges associated with the multilayer coatings, and report on progress to date. We have sputtered constant cl-spacing and depth-graded W / Si multilayers onto 0.3- 0.5 mm thick DURAN glass (AF45 and D263) and 0.4 mm thick epoxy replicated aluminum foils (ERAFs) , both of which are potential mirror substrates. We have characterized the interfacial roughness, uniformity, and stress of the coatings. The average interfacial roughness of each multilayer was measured from specular reflectivity scans (Bi = Br) using Cu K0 X-rays. The thin film stress was calculated from the change in curvature induced by the coating on flat glass substrates. Thickness and roughness uniformity were measured by taking specular reflectivity scans of a multilayer deposited on the inside surface of a quarter cylinder section. We found that interfacial roughness (a) in the multilayers was typically between 3.5 and 4.0 A on DESAG glass, and between 4.5 and 5.0 A on the ERAFs. Also, we found that coatings deposited on glass that has been thermally formed into a cylindrical shape performed as well as flat glass. The film stress, calculated from Stoney's equation, for a 200 layer graded multilayer was approximately 200 MPa. Our uniformity measurements show that with no baffles to alter the deposition profile on a curved optic, the layer thickness differs by "'203 between the center and the edge of the optic. Interfacial roughness, however, remained constant, around 3.6 A, throughout the curved piece, even as the layer spacing dropped off.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Harrison, Fiona A.0000-0003-2992-8024
Christensen, F. E.0000-0001-5679-1946
Additional Information:© 1997 Copyright SPIE--The International Society for Optical Engineering We acknowledge the support of NASA's SR&T (NAGW-1919) and SBIR (NASB-97016) programs. PHM acknowledges the support of a NASA GSRP Fellowship (NGT-50006).
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Non-Subject Keywords:hard X-ray astrophysics; multilayers; X-ray optics
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory1997-39
Record Number:CaltechAUTHORS:20141120-142647126
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52015
Deposited By: Deborah Miles
Deposited On:03 Dec 2014 01:44
Last Modified:09 Mar 2020 13:18

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