Ion resonance instability in the Eltrap electron plasma

A small fraction of ions can destabilize the diocotron mode (off axis rotation) of an electron plasma confined in a Malmberg-Penning trap. In this paper a set of experimental measurements performed in the ELTRAP device on the ions induced diocotron instability is presented. In particular, the dependence of the instability on the electron energy has been analyzed, by heating the plasma with a RF burst or by injecting into the trap electrons with different energies. A simple experimental technique to limit the instability is also described.