Abstract:

"When charged particle bunches travel at relativistic speeds through cavity-like discontinuities in an accelerator beam pipe, they excite electromagnetic resonant modes that can affect the motion of subsequent bunches and/or lead to excessive heating of surrounding structures. This beam–cavity interaction, commonly described through the concept of beam-coupling impedance, is a key factor limiting beam stability and overall accelerator performance. Traditional mitigation techniques, such as higher-order-mode (HOM) couplers or lossy ferrite materials, are effective but suffer from integration challenges and limited selectivity.

In this seminar, the exploration of a novel approach based on metamaterials will be presented. Metamaterials are one of the most intriguing developments in electromagnetism of the last 20 years, enabling innovative solutions across fields ranging from antenna design to imaging systems. Their electromagnetic response is determined not by their intrinsic material composition, but by their engineered sub-wavelength structuring. By tailoring this geometry, metamaterials can be designed to interact selectively with specific frequency bands.

This raises the main point of the talk: can metamaterial-based insertions be employed to effectively target and suppress harmful higher-order impedance modes? This presentation attempts to address the question and illustrate how metamaterials could open new pathways for more efficient and tunable impedance control in particle accelerators."