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 C2H12B10 are presented. As a result of boronization, the film with thickness up to 0.2 μm at deposition rate ∼25 nm/s was produced. The microhardness of the formed boron containing film H10 – 600, which indicates on structuredness of coating (the microhardness of the CVD B4C films was H100 – 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 ne = 1.3 × 1013 cm−3, Ip = 70 kA a shot duration was 350 ms and at the density of ne = 4.65 × 1013 cm−3, Ip = 70 kA was ∼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.