Structural analysis of diamond mosaic crystals for neutron monochromators using synchrotron radiation
(2013) In Diamond and Related Materials 37. p.41-49- Abstract
- The beams extracted from thermal neutron sources such as nuclear reactors are monochromatised by Bragg diffraction using imperfect single crystals with an angular mosaic spread of typically 0.2-0.8 degrees. For neutron wavelengths below 1.5 angstrom, the highest reflectivity of all crystalline materials is expected for diamond. Nowadays diamond single crystals with an appropriate mosaic spread exceeding a thickness of 1 mm can be grown by heteroepitaxy on an Ir/yttria-stabilised zirconia bilayer deposited on a Si(001) single crystal. To explain the observed neutron reflectivity being below the theoretically expected value, we have studied the spatial distribution of the mosaic structure of two crystals by high resolution X-ray diffraction... (More)
- The beams extracted from thermal neutron sources such as nuclear reactors are monochromatised by Bragg diffraction using imperfect single crystals with an angular mosaic spread of typically 0.2-0.8 degrees. For neutron wavelengths below 1.5 angstrom, the highest reflectivity of all crystalline materials is expected for diamond. Nowadays diamond single crystals with an appropriate mosaic spread exceeding a thickness of 1 mm can be grown by heteroepitaxy on an Ir/yttria-stabilised zirconia bilayer deposited on a Si(001) single crystal. To explain the observed neutron reflectivity being below the theoretically expected value, we have studied the spatial distribution of the mosaic structure of two crystals by high resolution X-ray diffraction using a laboratory X-ray source and synchrotron radiation. The first sample (A) showed a uniform mosaic spread of 0.18 degrees +/- 0.02 degrees across the 1 cm wide sample. The peak shift of the X-ray rocking curves of 0.08 degrees indicated a weak curvature of the crystal lattice. The measured absolute neutron peak reflectivity of 34% corresponded to 90% of the value predicted by theory. The peak width of the neutron rocking curve for the second sample (B) was twice as big, but here the peak reflectivity of 13% corresponded to only half of the theoretical value. This unfavourable behaviour could be assigned to a substantial spatial variation of the mosaic spread deduced from the synchrotron X-ray studies. X-ray diffraction with high spatial resolution indicated a mosaic block size below 50 pm for sample A. This was consistent with chemical etching experiments on the surface of a comparable sample which showed both randomly distributed dislocations and others that are arranged in boundaries of several 10 mu m large domains. (C) 2013 Elsevier B.V. All rights reserved. (Less)
Please use this url to cite or link to this publication:
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- author
- Fischer, M. ; Freund, A. K. ; Gsell, S. ; Schreck, M. ; Courtois, P. ; Stehl, C. ; Borchert, G. ; Ofner, A. ; Skoulatos, M. and Andersen, Ken LU
- organization
- publishing date
- 2013
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Diamond single crystal, Heteroepitaxy, Neutron monochromator, Mosaic, spread
- in
- Diamond and Related Materials
- volume
- 37
- pages
- 41 - 49
- publisher
- Elsevier
- external identifiers
-
- wos:000321536900006
- scopus:84878355371
- ISSN
- 0925-9635
- DOI
- 10.1016/j.diamond.2013.04.012
- language
- English
- LU publication?
- yes
- id
- 3f4f3058-bec6-45f8-a4ea-5e2f18d8bbd1 (old id 3975492)
- date added to LUP
- 2016-04-01 13:03:44
- date last changed
- 2022-01-27 17:06:31
@article{3f4f3058-bec6-45f8-a4ea-5e2f18d8bbd1,
abstract = {{The beams extracted from thermal neutron sources such as nuclear reactors are monochromatised by Bragg diffraction using imperfect single crystals with an angular mosaic spread of typically 0.2-0.8 degrees. For neutron wavelengths below 1.5 angstrom, the highest reflectivity of all crystalline materials is expected for diamond. Nowadays diamond single crystals with an appropriate mosaic spread exceeding a thickness of 1 mm can be grown by heteroepitaxy on an Ir/yttria-stabilised zirconia bilayer deposited on a Si(001) single crystal. To explain the observed neutron reflectivity being below the theoretically expected value, we have studied the spatial distribution of the mosaic structure of two crystals by high resolution X-ray diffraction using a laboratory X-ray source and synchrotron radiation. The first sample (A) showed a uniform mosaic spread of 0.18 degrees +/- 0.02 degrees across the 1 cm wide sample. The peak shift of the X-ray rocking curves of 0.08 degrees indicated a weak curvature of the crystal lattice. The measured absolute neutron peak reflectivity of 34% corresponded to 90% of the value predicted by theory. The peak width of the neutron rocking curve for the second sample (B) was twice as big, but here the peak reflectivity of 13% corresponded to only half of the theoretical value. This unfavourable behaviour could be assigned to a substantial spatial variation of the mosaic spread deduced from the synchrotron X-ray studies. X-ray diffraction with high spatial resolution indicated a mosaic block size below 50 pm for sample A. This was consistent with chemical etching experiments on the surface of a comparable sample which showed both randomly distributed dislocations and others that are arranged in boundaries of several 10 mu m large domains. (C) 2013 Elsevier B.V. All rights reserved.}},
author = {{Fischer, M. and Freund, A. K. and Gsell, S. and Schreck, M. and Courtois, P. and Stehl, C. and Borchert, G. and Ofner, A. and Skoulatos, M. and Andersen, Ken}},
issn = {{0925-9635}},
keywords = {{Diamond single crystal; Heteroepitaxy; Neutron monochromator; Mosaic; spread}},
language = {{eng}},
pages = {{41--49}},
publisher = {{Elsevier}},
series = {{Diamond and Related Materials}},
title = {{Structural analysis of diamond mosaic crystals for neutron monochromators using synchrotron radiation}},
url = {{http://dx.doi.org/10.1016/j.diamond.2013.04.012}},
doi = {{10.1016/j.diamond.2013.04.012}},
volume = {{37}},
year = {{2013}},
}