STUDY OF COLLECTIVE ION-ACCELERATION IN VACUUM

Theoretical and experimental studies of the collective acceleration of ions by a linear electron beam in an evacuated drift tube are presented. A one-dimensional theoretical model of the collective acceleration process that predicts accelerated proton energies of many times the electron-beam energy is presented. The formation of a virtual cathode downstream of the anode-cathode gap is discussed, and the subsequent movement of the virtual cathode downstream as the anode plasma expands allows for enhanced acceleration of ions trapped in the potential well of the virtual cathode. Experiments reported indicate that effective electron beam propagation and effective collective acceleration occurs when a plasma source initially well confined to the anode is present.