Anomalous Schottky Signals from a Laser-Cooled Ion Beam

Abstract

Longitudinal Schottky signals from a laser-cooled, spatially dense, ion beam have been studied in the ASTRID storage ring. The fluctuation signals are distorted by the effects of space charge, as is observed in electron cooling experiments. However, the spectra also exhibit previously unobserved coherent components. The ions' velocity distribution, measured by a laser fluorescence technique, suggests that the coherence is due to suppression of Landau damping. The observed behavior has important implications for the attainment of a crystalline ion beam in a storage ring.