Hot spot effect on infrared spectral luminance emitted by carbon under plasma particles impact

During the last Tore Supra campaigns, an anomalous deformation in the near infrared spectrum of radiation has been observed on neutraliser underneath the Toroidal Pumped Limiter (TPL) on which we have observed the growth of carbon layer. The consequence is the difficulty to assess the surface temperature of the components and the power loaded. Laboratory experiment has been performed, using an Electron Cyclotron Resonance (ECR) ions source, to reproduce, characterize and explain this phenomenon. The luminance emitted by Carbon Fibre Composite (CFC) and pyrolytic graphite, have been observed under 95 keV of H+ bombardments. The amplitude of the deformation was found to depend on the type of material used and the power density of the incident power loaded. This paper presents the possible hot spots explanation. The experimental luminance deformation is reproduced and these results are validated using a thermal model of dust in radiative equilibrium.