Analysis of carbon deposited layer growth processes in Tore Supra

Deposited layers in Tore Supra are graphitic disordered carbons and contain spherical nanoparticles, proving the existence of homogeneous growth within the plasma edge, in an unexpected state of advancement. Evidence of homogeneous catalysis comes from the observation of graphite-encapsulated metal particles. Here, carbon particle properties such as temperature and ablation rate in tokamak plasmas are modeled with the DUSTT code, showing that growth can occur in the far scrape-off-layer during normal operation of Tore Supra. These particles can be generated either through plasma chemistry, thanks to efficient trapping in the scrape-off-layer due to sheath repulsion, or through arcing, thanks to transient optimal conditions for catalysis. Their observation on the neutralizer surfaces shows that they are then transported, avoiding destruction.