Transcript Optical glasses under radiations

Optical glasses under radiations
Isabelle Savin de Larclause, DCT/AQ/LE
Toulouse, 11/05/10
Outline
■ Introduction
■ Schott glasses
■ Suprasil
■ ESA results
■ Ohara glasses
■ Luminescent
■ Conclusion
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Introduction
This presentation on radiation effect on optical material is principally
based on bibliography results, some CNES results are also
included.
 Radiations can modify the transmittance of the material (creation of
colored centers), but also the refractive index.
NB : 1Gy=100rad
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Schott glasses
All the Schott results is extracted from the Schott technical document TIE-42:
Radiation Resistant Optical Glasses.
Transmittance of non stabilized BK7 and stabilized BK7G18 before and after
irradiation
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Transmittance loss of BK7G18 as a function of wavelength for different kind
of radiations.
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Transmittance loss of different radiation stabilized glasses as a function of wavelength for
an absorption of 108 rad.
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CNES test on Schott glasses
■ Silex project : - LaK9G15 at 1Mrad → transmittance -0.5% for a
thickness of 5mm
- BK7G18 at 1Mrad → degradation < 0.2% for a
thickness of 4mm
 Picard project : - SF6G05 at 5krad → no degradation
- LaK9G15 at 5krad → -1.6% between 380nm and
390nm
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Suprasil
 Heraeus test : No degradation of visible transmittance after exposure to
Co60 γ-radiation (1.15 MeV) with 0.063 Mrad/h for 98 h→ 6,2Mrad
 CNES test : Silex project : 1Mrad → no degradation
 CNES background : used on several project (Jason, ISS laser target,
etc..) without any problem
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Ohara Glasses
All the Ohara results are extracted from the publication of Kyle B. Miller, James
Leitch, and Chandra Lyons-Mandel, in IEEE in 2001
The samples were irradiated with 152.5 MeV protons
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« As the protons pass through the material, they ionize impurities or dopants in
the glass. This ionization leads to creation of absorption sites (color centers)
and a net loss in the optical transmissivity. The loss is both wavelength
dependent and dopant dependent, with degradation greater in the near UV
wavelengths and virtually no degradation in the IR wavelengths.»
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Luminescence
Hardened glasses with cerium atoms, like BK7G14 is luminescent around 420nm under
radiation
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Conclusion
■ 2 main effects of the radiation : transmittance loss and refractive
index change
■ No significative transmission loss on hardened glasses for
exposure > 100krad
■ Sensibility of the refractive index of hardened glasses under
radiation
■ Very hight resistance of the Suprasil
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