Renewable boron carbide coating in plasma shots of tokamak T11-M

Experimental results on boronization in plasma shots of the tokamak T-11M are presented. Non-toxic and not explosive metacarborane C2H12B10 was used in the boron deposition process. Experiments have been carried out in shots with parameters: toroidal field ∼1-1.2 T, plasma current Ip = 70 kA, average shot duration tp ∼ 150 ms and electron density along the central chord ne ∼ 2.5 x 1013 cm-3. As a result of experiment, a dense film of ∼0.2 microns thickness with good adhesion to a surface has formed on the reference specimens after 8 s boronization. After boronization the impurities in wall areas have been suppressed. High vacuum characteristics of the discharge chamber were stabilized. Working vacuum was reached without a preliminary induction heating and cleaning by a glow discharge, and stabilization of the plasma filament has improved. Shot duration without disruption at densities of ne = 1.3 x 1013 cm-3, Ip = 70 kA was 350 ms and ne = 4.64 x 1013 cm-3, Ip = 70 kA was 250 ms. High repeatability of experimental results has appeared. Developed technology opens an opportunity of practical production of renewable structured boron-carbon coatings with use of plasma shots in large-scale tokamaks, such as DIII-D, JET, JT-60 UP, ITER, DEMO.