Superconductor magnesium diboride is considered one of the viable materials to substitute bulk niobium for superconducting radio frequency cavities. Utilizing a MgB 2 coating on the inner wall of a copper cavity will allow operation at higher temperatures (20-25 K) than Nb cavities due to the high transition temperature of MgB 2 (39 K) and the high thermal conductivity of Cu. In this paper, we present results of MgB 2 coating on Cu tubes with similar dimensions to a 3 GHz cavity, as the first step towards coating the actual cavity, using the hybrid physical chemical vapor deposition technique. The results show successful coating of a uniform MgB 2 layer on the inner wall of the Cu tubes with T c as high as 37 K.

We report on the growth of high quality MgB 2 thin films on silicon and silicon-on-insulator substrates by hybrid physical chemical vapor deposition. A boron buffer layer was deposited on all sides of the Si substrate to prevent the reaction of Mg vapor and Si. Ar ion milling at a low angle of 1°was used to reduce the roughness of the boron buffer layer before the MgB 2 growth. An Ar ion milling at low angle of 1°was also applied to the MgB 2 surface to reduce its roughness. The resultant MgB 2 films showed excellent superconducting properties and a smooth surface. The process produces thin MgB 2 films suitable for waveguide-based superconducting hot electron bolometers and other MgB 2 -based electronic devices.