A wireless method for beam coupling impedance bench measurement of resonant structures

The Beam Coupling Impedance (BCI) is a crucial aspect in the world of accelerator physics, as it describes the electromagnetic interactions between charged particle beams and the accelerator structure. The measurement and quantification of BCI is an essential requirement to assess and mitigate its impact, particularly when introducing new components or addressing issues in existing devices. The stretched Wire Method is a well-established technique for BCI evaluation, although it has well-known limitations particularly evident when dealing with cavity-like structures. In such cases, the estimates obtained below the cut-off frequency of the beam pipe can be inaccurate, where this frequency range holds particular relevance for many accelerator applications. To overcome these recognized limitations, an alternative bench measurement technique has been identified and thoroughly examined. This novel approach has been subjected to comprehensive testing in both virtual and real measurements, with a particular focus on a pillbox cavity.