  For the radiofrequency (RF) applications of normal conducting film with large
mean free path at high frequency and low temperature, the anomalous skin effect
differs considerably from the normal skin effect with field decaying
exponentially in the film. Starting from the relationship between the current
and the electric field (E field) in the film, the amplitude of E field along
the film depth is calculated, and is found to be non-monotonic. The surface
impedance is found to have a minimum value at certain film thickness. We apply
this calculation into a Cu coated S.S. beam pipe used in an accelerator to
reduce the ohmic power loss to determine the minimum thickness that should be
applied.
