Observations of Ordered Beams in CRYRING

In the CRYRING storage ring weak beams of electron-cooled highly charged ions have been studied. When the intensity of the ion beam decays below a certain limit the momentum spread of the beam show a sudden transition to a state with much lower momentum spread. Similar observations have earlier been made at GSI, and have been interpreted as a one-dimensional ordering of the beam. For a beam of 7.4 MeV/u Xe36+ we have varied the electron density and studied how that affects the particle number at transition, the momentum spread of the ion beam, and the Schottky power. The transition occurs at particle distances between 1 and 35 cm, depending on the cooling rate.