  Results of testing the fast CASCIE (Code for Accelerating Structures -
Coupled Integral Equations) code developed as an analytical-numerical tool for
studying the properties of inhomogeneous structured waveguides are presented.
We have used this code to numerically tune the resonator chain, which is very
similar to the classic 3m SLAC accelerating structure. During testing, we
discovered a problem that, in our opinion, was overlooked in the development of
the accelerating sections, namely the appearance of a constant phase shift when
determining the dimensions of the resonator radii from the characteristics of
homogeneous structures. This issue is particularly relevant in the development
of short accelerating structures.
