Transfer and Deposition of Carbon- and Nitrogen-containing Radicals and Ions Produced by Glow Discharge in Hydrogen/Methane/Nitrogen Mixtures A. E. Gorodetskiia, R. Kh. Zalavutdinova, V. L. Bukhovetsa, A. P. Zakharova, G. T. Razdobarin†,b, E. E. Mukhinb, and V. V. Semenovb a Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119991 Russia b Ioffe Physicotechnical Institute, Russian Academy of Sciences, Politekhnicheskaya ul. 26, St. Petersburg, 194021 Russia E-mail:
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Received November 11, 2007 Abstract — Transfer and deposition of the decomposition products of a dc glow discharge with hollow cathode in a hydrogen/methane flow are discussed. Hydrocarbon (a-C:H) films were deposited at inner surfaces of the hollow cathode and quartz tube bounded the discharge. The carbon deposition rate in the hollow cathode was 3–10 times higher than in the positive column and in afterglow range. Acetylene, ethylene, and ethane prevailed in the plasma-reaction gaseous products. When molecular nitrogen was introduced to the near-cathode plasma at a flow rate equal to or higher than that of methane, the carbon deposition rate at the cathode inner surfaces dropped down by 1.5 to 2 orders of magnitude. The carbon that has been consumed in the a-C:H films formation in the cathode is now transformed mainly to hydrogen cyanide (HCN). The carbon deposition rate in the positive column and in afterglow range (T = 300 K) were comparable with those in the H2/CH4 mixture. In the a-C/N:H deposits, the nitrogen concentration was 15 to 25 at %. The experiments showed that nitrogen can be used as a component of the gas flow specially introduced near the mirror in protecting the optical surfaces in diagnostic channels of the ITER tokamak against a-C:H film deposition. PACS numbers: 52.77.Bn; 52.77.Dq; 81.05.Uw; 81.15.Jj DOI: 10.1134/S0033173208060027
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