Radiation-hardening techniques of dedicated optical fibres used in plasma diagnostic systems in ITER B. Brichard a, * , A. Fernandez Fernandez a , H. Ooms a , F. Berghmans a , M. Decr  eton a , A. Tomashuk b , S. Klyamkin b , M. Zabezhailov b , I. Nikolin b , V. Bogatyrjov b , E. Hodgson c , T. Kakuta e , T. Shikama d , T. Nishitani f , A. Costley f , G. Vayakis f a SCKCEN, Belgian Nuclear Research Centre, Boeretang, 200, 2400 Mol, Belgium b FORC, Fiber Optic Research Centre, 38-119991 Moscow, Russia c Euratom-CIEMAT, 22-28040 Madrid, Spain d Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan e Japan Atomic Energy Research Institute, Naka 311-0193, Japan f ITER-JWS-Naka, Naka 311-0193, Japan Abstract This paper addresses the particular need to develop suitable fabrication techniques of glasses to improve the radi- ation-resistance and extend the lifetime of optical fibres in high radiation background. Two radiation hardening techniques based on hydrogen and fluorine doping of glass have been applied on step index pure silica core optical fibres. The radiation-induced optical absorption and luminescence have been measured in gamma and fission reactor irradiation conditions at SCKCEN, Mol Belgium. The experimental results show that the lowest optical absorption is achieved in the hydrogen-treated fibre sample. However, the luminescence effect remains significant in any type of fibre and cannot be reduced by the investigated radiation hardening techniques. Ó 2004 Elsevier B.V. All rights reserved. 1. Introduction Optical plasma diagnostic systems are usually com- binations of mirrors, lenses and windows to transport light emitted from the plasma edge to the remote diag- nostic area. The optical path is generally complex and involves numerous components. The practical attrac- tiveness of optical fibre to transport light contributes in reducing the complexity of the optical path design. Successful demonstrations of the application of the fibre technology in tokamak environment have been carried out in the early 90s at TFTR [1] and JET [2]. At that occasion, plasma diagnosticians used the optical fibres to transport the plasma emission to the diagnostic area where the light is spectrally dispersed to extract the plasma parameter information (e.g. charge exchange recombination spectroscopy). In contrast to TFTR and JET, ITER plasma diag- nostic systems [3] will have to face additional problems regarding radiation damage. Plasma pulse durations in ITERwilllasttypicallyseveralhundredseconds.During this period, the plasma will be producing a significant amount of radiation, implying in the long term signifi- cant radiation damage for components installed close to the plasma vessel. Consequently, chemical and physical properties of the material will change and in turn may compromise the performances of the systems. Inthecaseofopticalcomponentssuchassilicabased optical fibres, radiation affects the optical properties in * Corresponding author. Tel.: +32-143 32640; fax: +32-143 11993. E-mail address: bbrichar@sckcen.be (B. Brichard). 0022-3115/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jnucmat.2004.04.159 www.elsevier.com/locate/jnucmat Journal of Nuclear Materials 329–333 (2004) 1456–1460