Irradiation of KU1 and KS-4V substrate SiO2 overcoated Al mirrors

Piedad Martin; Teresa Hernandez; Andrei Goussarov; Eric R. Hodgson; Andrey M. Litnovsky; Mario Di Fino; Francesco Orsitto

doi:10.1016/j.fusengdes.2012.11.016

Irradiation of KU1 and KS-4V substrate SiO₂ overcoated Al mirrors

Piedad Martin, Teresa Hernandez, Andrei Goussarov, Eric R. Hodgson, Andrey M. Litnovsky, Mario Di Fino, Francesco Orsitto

Research output › peer-review

1 Scopus citations

Abstract

Previous work on overcoated dielectric mirrors identified several radiation problems; UV-visible reflectivity degradation, unreliability of manufacturers coating specifications, and conversion of SiO coatings to SiO₂ leading to swelling and cracking, and hence possible corrosion during LOCAs (loss of coolant accident). We report the results obtained for gamma and neutron irradiation of prototype mirrors with KU1 and KS-4V high purity silicas replacing the standard Pyrex substrate to overcome the problem of activation due to high impurity content. To avoid the SiO to SiO₂ conversion problem, the Al layer has been overcoated with SiO₂. The mirrors show high reflectivity (>80%) down to 200 nm. After gamma irradiation at 170 C in a dry nitrogen atmosphere to 10 MGy, no degradation in reflectivity was observed. They were then neutron irradiated in vacuum at 35 C to 6.8 × 10¹⁶ n/cm² (fast fluence) and reflectivity examined with a specially designed spectrometer system with a remote integrating sphere for hot cell use. Again no degradation in reflectivity was observed.

Original language	English
Pages (from-to)	1224-1227
Number of pages	4
Journal	fusion engineering and design
Volume	88
Issue number	6-8
DOIs	https://doi.org/10.1016/j.fusengdes.2012.11.016
State	Published - 2013

ASJC Scopus subject areas

Civil and Structural Engineering
Nuclear Energy and Engineering
General Materials Science
Mechanical Engineering

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10.1016/j.fusengdes.2012.11.016

Cite this

@article{556988d3005348e18027892e5bc2848d,

title = "Irradiation of KU1 and KS-4V substrate SiO2 overcoated Al mirrors",

abstract = "Previous work on overcoated dielectric mirrors identified several radiation problems; UV-visible reflectivity degradation, unreliability of manufacturers coating specifications, and conversion of SiO coatings to SiO2 leading to swelling and cracking, and hence possible corrosion during LOCAs (loss of coolant accident). We report the results obtained for gamma and neutron irradiation of prototype mirrors with KU1 and KS-4V high purity silicas replacing the standard Pyrex substrate to overcome the problem of activation due to high impurity content. To avoid the SiO to SiO2 conversion problem, the Al layer has been overcoated with SiO2. The mirrors show high reflectivity (>80%) down to 200 nm. After gamma irradiation at 170 C in a dry nitrogen atmosphere to 10 MGy, no degradation in reflectivity was observed. They were then neutron irradiated in vacuum at 35 C to 6.8 × 1016 n/cm2 (fast fluence) and reflectivity examined with a specially designed spectrometer system with a remote integrating sphere for hot cell use. Again no degradation in reflectivity was observed.",

keywords = "Dielectric mirrors, Irradiation effects, Reflectivity, X-ray photoelectron spectroscopy (XPS)",

author = "Piedad Martin and Teresa Hernandez and Andrei Goussarov and Hodgson, {Eric R.} and Litnovsky, {Andrey M.} and {Di Fino}, Mario and Francesco Orsitto",

note = "Acknowledgements The authors wish to thank J. Valle for his help in preparing the irradiation experiments and to C. Maffiotte for the XPS analysis of mirror surface. This work, supported by the European Communities under contracts of Association between Euratom/CIEMAT, and Euratom/SCK·CEN was carried out within the framework of the European Fusion Development Agreement. The views and opinions expressed herein do not necessarily reflect those of the European Commission.",

year = "2013",

doi = "10.1016/j.fusengdes.2012.11.016",

language = "English",

volume = "88",

pages = "1224--1227",

journal = "fusion engineering and design",

issn = "0920-3796",

publisher = "Elsevier",

number = "6-8",

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TY - JOUR

T1 - Irradiation of KU1 and KS-4V substrate SiO2 overcoated Al mirrors

AU - Martin, Piedad

AU - Hernandez, Teresa

AU - Goussarov, Andrei

AU - Hodgson, Eric R.

AU - Litnovsky, Andrey M.

AU - Di Fino, Mario

AU - Orsitto, Francesco

N1 - Acknowledgements The authors wish to thank J. Valle for his help in preparing the irradiation experiments and to C. Maffiotte for the XPS analysis of mirror surface. This work, supported by the European Communities under contracts of Association between Euratom/CIEMAT, and Euratom/SCK·CEN was carried out within the framework of the European Fusion Development Agreement. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

PY - 2013

Y1 - 2013

N2 - Previous work on overcoated dielectric mirrors identified several radiation problems; UV-visible reflectivity degradation, unreliability of manufacturers coating specifications, and conversion of SiO coatings to SiO2 leading to swelling and cracking, and hence possible corrosion during LOCAs (loss of coolant accident). We report the results obtained for gamma and neutron irradiation of prototype mirrors with KU1 and KS-4V high purity silicas replacing the standard Pyrex substrate to overcome the problem of activation due to high impurity content. To avoid the SiO to SiO2 conversion problem, the Al layer has been overcoated with SiO2. The mirrors show high reflectivity (>80%) down to 200 nm. After gamma irradiation at 170 C in a dry nitrogen atmosphere to 10 MGy, no degradation in reflectivity was observed. They were then neutron irradiated in vacuum at 35 C to 6.8 × 1016 n/cm2 (fast fluence) and reflectivity examined with a specially designed spectrometer system with a remote integrating sphere for hot cell use. Again no degradation in reflectivity was observed.

AB - Previous work on overcoated dielectric mirrors identified several radiation problems; UV-visible reflectivity degradation, unreliability of manufacturers coating specifications, and conversion of SiO coatings to SiO2 leading to swelling and cracking, and hence possible corrosion during LOCAs (loss of coolant accident). We report the results obtained for gamma and neutron irradiation of prototype mirrors with KU1 and KS-4V high purity silicas replacing the standard Pyrex substrate to overcome the problem of activation due to high impurity content. To avoid the SiO to SiO2 conversion problem, the Al layer has been overcoated with SiO2. The mirrors show high reflectivity (>80%) down to 200 nm. After gamma irradiation at 170 C in a dry nitrogen atmosphere to 10 MGy, no degradation in reflectivity was observed. They were then neutron irradiated in vacuum at 35 C to 6.8 × 1016 n/cm2 (fast fluence) and reflectivity examined with a specially designed spectrometer system with a remote integrating sphere for hot cell use. Again no degradation in reflectivity was observed.

KW - Dielectric mirrors

KW - Irradiation effects

KW - Reflectivity

KW - X-ray photoelectron spectroscopy (XPS)

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