SIMBUCA, using a graphics card to simulate Coulomb interactions in a Penning trap

In almost all cases, N-body simulations are limited by the computation time available. Coulomb interaction calculations scale with O(N^2) with N the number of particles. Approximationmethods exist already to reduce the computation time to O(N logN), although calculating the interaction still dominates the total simulation time.We present Simbuca, a simulation package for thousands of ionsmoving in a Penning trap whichwill be applied for the WITCH experiment. Simbuca uses the output of the Cunbody-1 library, which calculates the gravitational interaction between entities on a graphics card, and adapts it for Coulomb calculations. Furthermore the program incorporates three realistic buffer gasmodels, the possibility of importing realistic electric andmagnetic fieldmaps and different order integratorswith adaptive step size and error control. The software is released under the GNU General Public License and free for use.