Optimization of non-oxidative carbon-removal techniques by nitrogen-containing plasmas

• Published in: Journal of nuclear materials Vol. 390; pp. 593 - 596
• Main Authors: Ferreira, J.A., Tabarés, F.L., Tafalla, D.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15-06-2009; Elsevier
• Subjects: Applied sciences; Controled nuclear fusion plants; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fuels; Installations for energy generation and conversion: thermal and electrical energy; Nuclear fuels; 52.75.Rx; 33.15.Ta; 52.40.Hf; Tokamak; Plasma; Gas mixture; Glow discharge; Tritium; Nitrogen; Helium; Carbon; Optimization; Nuclear reactor; Nuclear fusion reactor; Laser; Surface plasma interaction; Safety; Mass spectrometry; Erosion; Interferometry
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2009.01.121

The continuous control of tritium inventory in ITER calls for the development of new conditioning techniques [G. Federici et al., Nucl. Fus. 41 (2001) 1967]. For carbon plasma-facing components, this implies the removal of the T-rich carbon co-deposits. In the presence of strong oxygen getters, such Be, the use of oxygen-based techniques will be discouraged. In addition, tritiated water generated by these techniques poses extra problems in terms of safety issues [G. Saji, Fus. Eng. Des. 69 (2003) 631; G. Bellanger, J.J. Rameau, Fus. Technol. 32 (1997) 196; T. Hayashi, et al., Fus. Eng. Des. 81 (2006) 1365]. In the present work, oxygen-free (nitrogen and ammonia) glow discharge plasmas for carbon film removal were investigated. The following gas mixtures were fed into a DC glow discharge running in a ∼200
nm carbon film coated chamber. Erosion rate was measured in situ by laser interferometry, RGA (Residual Gas Analysis) and CTAMS (Cryotrapping Assisted Mass Spectrometry) [J.A. Ferreira, F.L. Tabarés, J. Vac. Sci. Technol. A25(2) (2007) 246] were used for the characterization of the reaction products. Very high erosion rates (similar to those obtained in helium–oxygen glow discharge [J.A. Ferreira et al., J. Nucl. Mater. 363–365 (2007) 252]) were recorded for ammonia glow discharge.