MgB$_{2}$ Coating by HPCVD for 1.3-GHz Superconducting RF Cavities

While MgB₂ possesses promising material parameters for SRF cavities with higher Q, higher gradient, and higher operation temperatures than Nb cavities, such cavity properties have not been demonstrated using MgB₂. As part of a continuing effort to fabricate MgB₂-coated SRF cavities by hybrid physical chemical vapor deposition (HPCVD), we present here an HPCVD system design for coating the inside wall of 1.3-GHz copper cavities with MgB₂. The cavity is heated using a pair of clamshell resistive heaters that directly contact the cavity body. Here, the new heater design is more compact and requires less power to reach the deposition temperature (~500°C for MgB₂ deposition on copper.) Preliminary test of MgB₂ films grown on small copper substrates, mounted at different locations on the cavity, shows T_c of 28.4 ~ 34.3 K, measured by AC susceptibility.