Theoretical Analysis of Metamaterial Insertions for Resistive-wall Beam-coupling Impedance Reduction

Resistive-wall impedance usually constitutes a significant percentage of the total beam-coupling impedance budget of an accelerator. Reduction techniques often entail high electrical-conductivity coatings. This paper investigates the use of negative-permittivity or negative-permeability materials for sensibly reducing or theoretically nearly cancelling resistive-wall impedance. The proposed approach is developed by means of an equivalent transmission-line model. The effectiveness of such materials is discussed both for negative-permittivity and for negative-permeability cases, which actually show different impacts and can be then target of proper engineering. This first-stage study opens the possibility of considering metamaterials for impedance mitigation or for proper experimental setups.