HOM-free accelerating dielectric cavities with metallic inclusions

Previous investigations demonstrated that point-defected photonic bandgap cavities based on periodic and aperiodic dielectric arrangements can be successfully employed as single cell in particle accelerators. In this paper, we present a study aimed at highlighting the possible advantages of using hybrid structures based on the above dielectric configurations, but featuring metallic rods in the outermost regions, for the design of accelerating resonators of extremely high-quality factor. In this framework, we consider diverse configurations, with different (periodic and aperiodic) lattice geometries, sizes, and dielectric/metal fractions. The use of superconducting plates to further increase the cavity performances is taken into account. Results from our comparative studies, based on numerical full-wave simulations backed by experimental validations (at room and cryogenic temperatures) in the microwave region, identify the candidate parametric configurations capable of yielding the highest quality factor. © Società Italiana di Fisica.