Near infrared spectra of carbon deposited layers from Tore Supra under plasma particle bombardment
For long discharges in tokamaks as Tore Supra, great attention must be paid to prevent overheating of the Plasma Facing Components (PFCs). Tore Supra explores the possibility to provide a comprehensive safety system using thermography. With infrared (IR) thermography, the surface temperature of PFCs is deduced assuming that they radiate as a grey body with a uniform temperature distribution in the field of view and in the case of carbon with a high emissivity coefficient Sigma 0.8. During the 1999 experimental campaign of Tore-Supra, spectral luminance has observed, in the near infrared range 0.9 . 1.55 µm, on neutraliser plates of the Modular Pump Limiter (MPL) that could not be described with these assumptions. Spectral luminance distributions deviating from a Planck distribution make it difficult to obtain a well defined surface temperature. To explain the observed modified spectra, contributions from dust and/or strong temperature gradients in the surface layers have been proposed. These neutraliser plates made of pyrolitic graphite were covered with flaky carbon deposits of up to 200 µm of thickness. In 2002, during the initial phase directly after the installation of the new PFCs, similar results on the neutralisers placed underneath the Toroïdal Pumped Limiter (TPL) have also been observed. Later in the campaign when the leading edge of the TPL.s neutraliser was completely covered with deposited carbon, the spectral luminance observed was in good agreement with the assumptions of a grey body (Sigma. 0.8) and a uniform temperature distribution in the field of view. Here we present results of laboratory investigations that show spectral luminance distributions similar to those obtained in the Tokamak experiments.
Bibliographic Reference: An oral paper given at: 30th EPS Conference on Controlled Fusion and Plasma Physics Organised by: European Physical Society Held at: St. Petersburg, Russia, 7-11 July 2003 Proceedings available online at: http://eps2003.ioffe.ru/
Availability: Available from Association EURATOM-CEA, Département de Recherches sur la Fusion Contrôlée, CEA Cadarache, F-13108 St Paul-Lez-Durance, France Tel: (+33) 4 42 25 70 01; Fax: (+33) 4 42 25 64 21 E-mail: email@example.com
Record Number: 200317058 / Last updated on: 2003-10-29
Original language: en
Available languages: en