Laser Cooling of Intense Relativistic Ion Beams

Doppler laser cooling is a technique to reduce the longitudinal momentum spread of an ion beam in a circular accelerator. In the past, the principle was investigated and verified on non-relativistic ion beams. Within the FAIR project, laser cooling will be applied to high intensity and relativistic ion beams for the first time. Laser cooling results in a further increase of the longitudinal ion density and creates exotic longitudinal phase space distributions. In order to ensure stable operation and optimize the cooling process, this dissertation numerically investigates the particle dynamics and the interplay of the laser force and high intensity effects. This work describes the ion-photon interaction and derives the laser force on ions at relativistic energies. The force is calculated for continuous wave and pulsed laser excitations. The pulsed laser excitation results in a broadband force, which interacts with all ions simultaneously, whereas the width of the continuous wave laser force is typically three to four orders of magnitude smaller. In order to interact with all ions, the position of the continuous wave laser force is scanned during the cooling process. The particle dynamics during the cooling processes for both laser forces are analyzed and compared. The impact of heating effects during the laser cooling process is also investigated. Scattering events within the beams limit the maximum ion intensity for the cooling for both a continuous wave or a pulsed laser system. In addition, numerical simulations show two instabilities, that arise during the scan of the continuous wave laser force and are triggered by space charge. This work describes the development of the instabilities and the impact on the laser cooling process. Analytical expressions for the threshold of instabilities and maximum ion intensities are given. The scaling of the cooling process and intensity limitations with beam energy is discussed in order to evaluate the prospects of laser cooling experiments at relativistic energies. The work concludes with the comparison of the cooling process of non-relativistic carbon ions and relativistic titanium ions. The comparison emphasizes the main challenges for laser cooling experiments in the SIS100 synchrotron at FAIR