In the injector section of electron linacs, both internal space charge forces and wakefield effects influence the beam dynamics. So far, existing simulation approaches can not account for both effects simultaneously. To fill this gap, we have developed a computational method to account for both effects self-consistently*. It couples a space charge solver in the rest frame of the bunch with a wakefield solver by means of a scattered field formulation. The novelty of this approach is that it enables us to simulate the creation of wakefields throughout the emission and acceleration process. In our contribution, we present extensive studies of the coupled wakefield and space charge effects in a traveling wave electron gun under development at the Paul Scherrer Institute. Wakefields created by the multi-cell design and the transition to the beam pipe are accounted for. Hence, the respective influences of these causes for geometric wakefields on particle dynamics are compared, providing detailed insights into the coupling of wakefields on bunches at low energies. Specifically, uncorrelated energy spread and emittance are investigated which are of key interest for FEL operation.

In the injector section of electron linacs, both internal space charge forces and wakefield effects influence the beam dynamics. So far, existing simulation approaches can not account for both effects simultaneously. To fill this gap, we have developed a computational method to account for both effects self-consistently*. It couples a space charge solver in the rest frame of the bunch with a wakefield solver by means of a scattered field formulation. The novelty of this approach is that it enables us to simulate the creation of wakefields throughout the emission and acceleration process. In our contribution, we present extensive studies of the coupled wakefield and space charge effects in a traveling wave electron gun under development at the Paul Scherrer Institute. Wakefields created by the multi-cell design and the transition to the beam pipe are accounted for. Hence, the respective influences of these causes for geometric wakefields on particle dynamics are compared, providing detailed insights into the coupling of wakefields on bunches at low energies. Specifically, uncorrelated energy spread and emittance are investigated which are of key interest for FEL operation.

The beam coupling impedance is a key design parameter for all accelerator structures. Recently, we have introduced a novel simulation approach for impedance calculations in 3D-geometry. Unlike conventional methods, this approach is based on the solution of Maxwell’s equations in the frequency domain using a high-order finite element technique. The main challenge for all impedance simulations, however, is the huge amount of computational resources that is required for the numerical discretization of electromagnetically large accelerator structures. In this contribution, we introduce a specialized domain decomposition technique for impedance simulations. The technique allows to handle large accelerator structures by decomposing the computational domain into subdomains that interact by means of suitably chosen boundary conditions. We describe a class of such boundary conditions that accurately take into account the modal wave contributions traveling through domain interfaces in the presence of a particle beam. An application of the method considered in the paper is the full impedance characterization of a large in-vacuum undulator for the PETRA IV synchrotron source.