Vacuum Arc Deposited Boron Carbide Films for Fusion Plasma Facing Components

Boron carbide is an ideal coating for radio-frequency antennas in magnetic fusion energy, due to a combination of desirable properties: high hardness at high temperature, high melting point, low Z and high thermal conductivity. In this paper, the feasibility of using vacuum arc technology for coating antennas and other magnetic fusion energy plasma facing components is explored. This technique has the potential of producing much denser film than plasma spray and substantially higher deposition rates than magnetron sputtering. In addition, the use of hyper-thermal species may result in the formation of high thermal conductivity crystalline phase at lower deposition temperatures than would otherwise be expected. Finally, the compatibility of the vacuum arc with ultra-high vacuum conditions raises the possibility of in situ repair of components in a fusion reactor. Initial deposition studies are presented, which produced primarily amorphous film, but with the correct stoichiometry and a high deposition rate (>10nm/s). The properties of this film are presented in this paper. Some of the properties of the vacuum arc discharge, the first to be operated successfully with a sintered boron carbide cathode, are also presented.