Towards a Cryogen-Free MgB$_{\mathrm{2}}$-Based Superconducting Radio Frequency Accelerating Cavities

Studies on the application of Magnesium diboride (MgB$_{\mathrm{2}})$ superconducting films have shown promise for use with the radio-frequency (SRF) accelerating cavities. MgB$_{\mathrm{2\thinspace }}$coating is a potential candidate to replace bulk niobium (Nb) SRF cavities. The ultimate goal of our research is to demonstrate MgB$_{\mathrm{2}}$ coating on copper cavities to allow operation at about 20 K or so as a result of the high transition temperature (T$_{\mathrm{c}})$ of MgB$_{\mathrm{2}}$ and taking advantage of the excellent thermal conductivity of copper. Here, we will report on our recent experimental results of applying hybrid physical-chemical vapor deposition (HPCVD) to grow MgB$_{\mathrm{2}}$ films on 2-inch diameter copper discs as well as on a 2.8 GHz resonator cavity