Inert gas plasma spraying for cavity stiffening using copper coating

Superconducting cavities required a high mechanical stability not to be affected by Lorentz forces detuning or by external mechanical vibrations which could induce large frequency changes. One possibility to improve the mechanical stability of SRF cavities is to coat the external cavity surface with an appropriate material. Since a few years, we have studied different coating techniques and materials, which could be used for this stiffening method. The thermal and mechanical properties of the different coatings obtained have been systematically measured and compared. An interesting process, the inert gas plasma spraying has been recently investigated: the copper coating obtained is characterized by a low porosity and a reduced oxidation. Measurements performed on samples showed that the coating meet the required thermal and mechanical performances. From the industrial feasibility point of view, this method is fully realistic and brings interesting performances at moderate costs. (author)