Absolute cross sections for fast electron ejection by swift highly charged ions and evidence for ''Fermi shuttle'' acceleration

We report the results of recent experiments performed at the CS (Catania) and GANIL (Caen) cyclotron accelerators, with 45 A MeV 19+ and 28+58Ni and 95 A MeV 18+36Ar pulsed beams, respectively. Electron velocity spectra were measured in a large angular range with different target foils (C, Al, Ni, Ag, Au). Besides electrons with the beam velocity (convoy electrons, CE) and two times the beam velocity (binary encounter electrons, BE), we observe also a high velocity tail in the case of the Au target only, which can be explained by a ''Fermi-shuttle'' mechanism. We also give absolute BE and CE production cross-sections. As a preliminary result of the recent GANIL experiment, we observe the lack of the CE component at the most forward angles in the case of the carbon target. For the other targets the CE yield increases as a function of the target atomic number. (orig.)