Calculations of resonance enhancement factor in axion-search
  tube-experiments
  It is pointed out that oscillating current density, produced due to the
coupling between an external magnetic field and the cosmic axion field, can
excite the TM resonant modes inside an open-ended cavity (tube). By
systematically solving the field equations of axion-electrodynamics we obtain
explicit expressions for the oscillating fields induced inside a cylindrical
tube. We calculate the enhancement factor when a resonance condition is met.
While the power obtained for TM modes replicates the previous result, we
emphasize that the knowledge of explicit field configurations inside a tube
opens up new ways to design axion experiments including a recent proposal to
detect the induced fields using a superconducting LC circuit. In addition, as
an example, we estimate the induced fields in a cylindrical tube in the
presence of a static uniform magnetic field applied only to a part of its
volume.
