BEAM-CAVITY INTERACTIONS IN THE RING CYCLOTRON

Beam excited Higher Order Modes (HOMs) are observed in the cavities of the Ring Cyclotron. Since a self consistent simulation is not feasible, a simplified computation method is developed: The parallel eigensolver Omega3P of the Stanford Linear Accelerator Center (SLAC) allowed us to calculate the eigenmodes of the entire Ring Cyclotron for the first time ever. The RF fields are expanded onto a superposition of these modes and the excitation is calculated in the frequency domain. Trajectories of the particles in the static magnetic field, superimposed with the space charge fields and the beam excited HOMs, are then simulated. The simulation results confirm that only a small deformation of the charge distribution appears up to proton beam currents of 2 mA