Proof-of-principle demonstration of Nb_3Sn superconducting radiofrequency cavities for high Q_0 applications

摘要

Many future particle accelerators require hundreds of superconducting radiofrequency (SRF) cavities operating with high duty factor. The large dynamic heat load of the cavities causes the cryogenic plant to make up a significant part of the overall cost of the facility. This contribution can be reduced by replacing standard niobium cavities with ones coated with a low-dissipation superconductor such as Nb_3Sn. In this paper, we present results for single cell cavities coated with Nb_3Sn at Cornell. Five coatings were carried out, showing that at 4.2 K, high Q_0 out to medium fields was reproducible, resulting in an average quench field of 14 MV/m and an average 4.2 K Q_0 at quench of 8 × 10~9. In each case, the peak surface magnetic field at quench was well above H_(c1), showing that it is not a limiting field in these cavities. The coating with the best performance had a quench field of 17 MV/m, exceeding gradient requirements for state-of-the-art high duty factor SRF accelerators. It is also shown that-taking into account the thermodynamic efficiency of the cryogenic plant-the 4.2 K Q_0 values obtained meet the AC power consumption requirements of state-of-the-art high duty factor accelerators, making this a proof-of-principle demonstration for Nb_3Sn cavities in future applications.