On RF residual losses and phonon generation

One restriction against applying superconducting rf cavities is the achievable rf residual surface resistance Rres, especially after surface damage. A theory is presented, where by interfacial quantum mechanic exchange between conduction band and localized states, momentum of the shielding current is transfered to the traps. For rf shielding currents this oscillating force on the localized states coherently generates transverse phonons. This transfer of momentum, due to the overlap of band and trap states, corresponds to an rf residual resistance which, for the first time, is able to describe consistently the observed Rres. In addition, the presented theory explains microscopically the observed rf-phonon-coupling.