Observations of Ordered Ion Beams in Cryring

A sudden drop in momentum spread of electron-cooled beams of highly charged Ni and Xe ions, similar to what has earlier been seen at GSI, has been observed at CRYRING. The transition occurs at particle distances between 1 and 35 cm depending on the cooling rate, and it has been interpreted as an ordering of the ion beam. We have studied how the particle number and the momentum spread at the transition depend on the electron density in the cooler. We have also observed that the drop in momentum spread is accompanied by a reduction in Schottky power when the electron density is high.