Renewed first wall coating in plasma shots at the T-11M tokamak

Experimental results on boronization in situ in the tokamak T-11M plasma shots using non-toxic and not explosive metacarborane C(2)H(12)B(10) are presented. As a result of boronization, the film with thickness up to 0.2 mu m at deposition rate similar to 25 nm/s was produced. The microhardness of the formed boron containing film H(10) - 600, which indicates on structuredness of coating (the microhardness of the CVD B(4)C films was H(100) - 1800). Injection of carborane in the plasma shots has improved a stabilization of plasma filament. The impurities in wall area have been suppressed, high-vacuum characteristics of the discharge chamber were stabilized. Plasma shot duration without disruption increased essentially. At the density of n(e) =1.3 x 10(13) cm(-3), I(p) = 70 kA a shot duration was 350 ms and at the density of n(e) = 4.65 x 10(13) cm(-3), I(p) = 70 kA was similar to 250 ms. High repeatability of experimental results has appeared. Boronization results in to an essential decrease of the volt-second consumption rate and, correspondingly, to an increase of shot duration. Developed technology opens an opportunity of practical production of renewed structured boron-carbon coatings using of plasma shots in existing large-scale tokamaks and plasma devices. (C) 2010 Elsevier B.V. All rights reserved.