Barrier bucket systems are planned for the SIS100 Synchrotron (part of the future accelerator facility FAIR) and the ESR storage ring to facilitate several longitudinal beam manipulations [9] [15]. In order to achieve a single-sine gap signal of the desired amplitude and quality, effects in the linear and nonlinear region of the RF systems have to be investigated and included in the design of the overall system. Therefore, the cavities and the amplifier stages are to be modeled in PSpice. In this contribution, a cavity model will be presented. In a first step, a model for the magnetic alloy (MA) ring cores, which highly account for the properties of the cavity, has been found based on measurement data. In a second step, the future setup of ...