Study of the anomalous skin effect of normal conducting film

TL;DR

This paper investigates the anomalous skin effect in normal conducting films at high frequency and low temperature, revealing non-monotonic electric field behavior and optimal film thickness for minimal surface impedance.

Contribution

It provides a theoretical analysis of the anomalous skin effect, including electric field distribution and surface impedance, and applies findings to optimize copper-coated stainless steel beam pipes.

Findings

Electric field amplitude along the film is non-monotonic.

Surface impedance has a minimum at a specific film thickness.

Optimal film thickness reduces power loss in accelerator components.

Abstract

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.