Real-time detector for plasma diagnostic in antimatter experiment

In the ATHENA experiment, which has recently produced and detected cold antihydrogen, the antiatoms formation is performed by mixing two cold (meV) charged clouds of positrons and antiprotons. The antihydrogen production is strictly dependent on positron plasma parameters. For this purpose we developed a new system to investigate such properties in a non-destructive way. The method is based upon the measurement of the plasma response under a frequency sweep RF excitation and its subsequent analysis. Plasmas trapped in Penning trap exhibit typical resonant collective modes characterized by frequencies, amplitudes and widths dependent on the particle number, density, spatial extent and temperature. With this system it is so possible to have a real-time monitor of the plasma during antihydrogen production.