Synchronization effect in an ion trap resonator

Abstract

Abstract.Using a resonator-like electrostatic ion trap, we demonstrate that, under certain condition, it is possible to keep constant the width of a packet of ions oscillating between two mirrors. We show, using one dimensional calculations, that the effect is the result of Coulomb repulsion which, in a counter-intuitive way, keeps the ions together. Preliminary results of the exploitation of this phenomenon for high precision mass spectrometery are given. I INTRODUCTIONThe dynamics of a cloud of ions stored in an ion trap has been the subject of extensive studies for many years [1]. Using various techniques of cooling, such as laser cooling, it has been shown that transitions from "gas" to "liquid" and finally to "solid" phases can be observed. In this last case, ordering is achieved by the superposition of a strong external focusing force and the Coulomb repulsive force between the stored ions. In general, very low temperatures are needed in order to bring the system to an "organized" state, and usually the experiments can be performed with only a limited set of ions, such as Li+, Be+ and Mg+.During the last four years, our group (at the Weizmann Institute of Science) has developed and studied a new type of ion trap [2,3], in which fast (keV) ions are stored between two electrostatic mirrors, much like photons in an optical resonator. This ion trap has been used for the study of metastable negative ions [4,5], metastable states in atomic and molecular ions [6,7], and collision induced dissociation, using a beam extraction scheme [8]. In these studies, the trap was used as a "cooling" device, where the excited states produced by the ionization process in the ion source were allowed to decay. Recently [9], we have found that a certain type of ordering can be achieved in such a device with ions at high temperature (,,_ 1 eV). In this paper, we present a short overview of this new phenomenon which is related to the dynamics of small bunches of ions oscillating between the trap CP606, Non-Neutral Plasmna Physics IV, edited by F. Anderegg et al.