The ELTRAP device installed at the Department of Physics of the University of Milan is a Malmberg–Penning trap, with a magnetic field up to 0.2 T, equipped with charge coupled device optical diagnostics. It is intended to be a small scale facility for electron plasma and beam dynamics experiments, and in particular for the study of collective effects, equilibrium states, and the formation of coherent structures in these systems. The device features a relatively long solenoid, corrected by 4 shims and 16 dipole coils, in order to obtain a large uniform magnetic field region. The modular electrode design allows several variations of the experimental configuration. The first experiments which assess the operation of the facility are described. Plasma confinement times up to several minutes have been obtained and an electron temperature of 4–8 eV has been measured.

An investigation of the ions induced diocotron instability in an electron plasma confined in a Malmberg-Penning trap is presented. The detection of the instability is based on the spectral analysis of the induced charge signals on the walls of the confining electrodes, which allows tracking of the plasma displacement from the axis. The dependence of the instability on the electron energy is analysed by three different methods: (i) injecting electrons with different energies, (ii) heating the electrons with a single radio frequency burst, (iii) varying the ramp-up time of the confining voltage. An experimental technique to limit the ion resonance instability, based on the application of suitable potentials on a set of electrodes, is presented.

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