EIGENMODE COMPUTATION FOR THE GSI SIS18 FERRITE CAVITY

At the GSI Helmholtzzentrum fur Schwerionen- forschung in Darmstadt the heavy-ion synchrotron SIS18 is operated to further accelerate stable nuclei of elements with different atomic numbers. Two ferrite-loaded cavity resonators are installed within this ring. During the accel- eration phase their resonance frequency has to be adjusted to the revolution frequency of the heavy ions to reflect their increasing speed. To this end, dedicated biased ferrite-ring cores are installed inside the cavities for a broad frequency tuning. By properly choosing a suited bias current, the dif- ferential permeability of the ferrite material is modified, which finally enables to adjust the eigenfrequency of the resonator system. Consequently, the actual resonance fre- quency strongly depends on the magnetic properties of the ferrites. The goal of the current study is to numerically de- termine the lowest eigensolutions of the GSI SIS18 ferrite- loaded cavity. For this purpose, a new solver based on the Finite Integration Technique has been developed.