Surface Rf Magnetic Field Enhancement Due To Closely Spaced Cylindrical Protrusions

The magnetic field enhancement caused by closely spaced, cylindrical, metallic protrusions in an rf cavity is studied theoretically and compared to field solver results for such micro-structures. It is found that the enhancement between the protrusions can be large when the magnetic field is perpendicular to the gap between them, and that the enhancement increases as this gap is reduced. This mechanism could help explain the observation of melting on normal-conducting cavity surfaces subjected to non-enhanced pulsed heating well below that required to melt the surface material. It could also help explain quenching in superconducting cavities when the nominal magnetic fields are below the critical value. (C) 2014 AIP Publishing LLC.