A study on collective acceleration of barium ions

Barium iOLs were collectively accelerated to a peak energy on order of GeV using an intense relativistic electron beam (IREB). The IREB generator used was a Physics International Pulserad 110A which produces a 1.5-MV, 27-kA, 30-ns pulse in a conventional diode configuration. Two rail-type plasma guns with barium electrodes produced a barium plasma in a partitioned space (the anode space), which was used as a plasma anode and as an ion source. Electrons field-emitted from a 3-mm-diam tungsten cathode were injected into vacuum through this plasma. Without this preformed barium plasma, an IREB could hardly propagate in a drift tube (30 cm long and 16 cm in diameter). At the best timing of firing, the peak kinetic energy of beam electrons and the peak beam current at 20 cm from the cathode were 1.3 MeV and 16 kA respectively. Ion energies were measured using a time-of-flight method and stacked foil-8SNTD (solid state nuclear track detector) combinations. From the time-of-flight, the maximum ion energy was 7.4 MeV/amu., which corresponds to 1.0 GeV for barium ions. Ions with energy above 1.8 GeV were detected using a stacked aluminum foil-8SNTD combination.