IMPEDANCE CRLCULC\TION m RF CFlVITIES FILLED WITH GYROTROPIC LOSSY MATERIfAL

Usually ferrites are used in tunable cavities of particle accelerators hardware. Properties of ferrite5 (especially permeability) strongly depend on frequency. fittempts to use usual codes (like SUPERFISH Cl31 to evaluate RF cavity characteristics in wide frequency range give unreliable results. Using finite element5 method, special code was developed to calculate fields, exited b!. beam current, in cavities with either rotational or translational symmetry and arbitrary cross-section, be1 “W cut-off. In general case nonhermitian tensor with frequency dependent components describes the properties of material. Some examples of application are given. JNTRDDUCTION One of most serious problem in the development of high intensity cyclic accelerators is one to construct chamber with possible low impedance. In f requencv range be1 ow..ilt-of f are essent i al narrow-band impedances due to RF cavities of the accelerating system. Rs usual, to change operating frequency during accelerating cycle, RF cavities partially filled with ferrite are used. The permeability of the ferrite essential 1 y depends on frequency and RF 1 asses in ferrite may exceed RF losses in cavity walls in several orders. For these reasons problem of simulation of the electromagnetic field distribution (especially for high order modes) can not come to 1 i near eigenvalue problem, as it is done in usual codes for RF cavities calculations. FORMULATION:?- THE PROBLEM _-- _ __I Consider the problem of excitation of the cavity with driving beam current given by j = j