Simulation and observation of the long-time evolution of the longitudinal instability in a cooler storage ring

In the ESR heavy-ion cooler storage rings at GSI the exponential growth and the subsequent saturation phase of the longitudinal instability in space c harge dominated ion beams can be monitored with high resolution. Kinetic si mulations together with the experimental data lead to a new insight into th e effects of space charge and electron cooling on the long-time evolution o f the instability. In the simulations we observe the continuous excitation of long-lived collective modes generated by particle trapping in the self-e xcited potential, which suggest that previous "overshoot" concepts need rev ision. [S0031-9007(99)08941-3].