Experiments on the beam dynamics and on the internal cooling of ions stored in a linear electrostatic
ion beam trap operated at < 15K are reported. The extremely low density of residual gas and resulting long storage times afforded by the cold environment have enabled observation of ion bunches maintained by a self-synchronizing mechanism for up to 12 s. The experiment is compared with a model of the bunch decoherence process to illuminate the mechanisms behind both the long persistence of the bunches and their eventual decay into a continuous beam. In a different experiment the change in the vibrational temperature of stored
cluster anions via radiative cooling was monitored by using the laser-induced detachment of electrons as a diagnostic.