M. Bussmann

The dynamics of bunched laser-cooled ion beams at relativistic energies

We discuss the axial dynamics of laser-cooled relativistic C3+ ion beams at moderate bunching voltages. Schottky noise spectra measured at a beam energy of 122 MeV/u are compared to simulations of the axial beam dynamics. Ions confined in the bucket are addressed by the narrow-band force of a laser beam counter-propagating to the ion beam, while the laser frequency is detuned relatively to the cooling transition frequency in the rest frame of the bucket. At large detuning comparable to the momentum acceptance of the bucket, the axial dynamics can be well explained by the secular motion of individual non-interacting ions. At small detuning, corresponding to a small axial momentum spread Δpaxial/paxial < 10−6 of the ions, the measured Schottky noise spectra can no longer be explained using an approach which neglects the ion-ion interaction. Instead, the model fails when the ion bunch enters the space-charge dominatedregime, at which the mutual Coulomb-energy of the ions becomes comparable to the kinetic energy of the ions.

Simulating strongly coupled plasmas at low temperatures

Realistic molecular dynamics (MD) simulations of the particle dynamics in strongly coupled plasmas require the computation of the mutual Coulomb‐force for each pair of charged particles if a correct treatment of long range correlations is required. For plasmas with N > 104 particles this requires a tremendous number of computational steps which can only be addressed using efficient parallel algorithms adopted to modern super‐computers.We present a new versatile MD simulation code which can simulate the non‐relativistic mutual Coulomb‐interaction of a large number of charged particles in arbitrary external field configurations. A demanding application is the simulation of the complete dynamics of in‐trap stopping of highly charged ions in a laser cooled plasma of N = 105 24Mg+ ions. We demonstrate that the simulation is capable of delivering results on stopping times and plasma dynamics under realistic conditions. The results suggest that this stopping scheme can compete with in‐trap electron cooling and m...