Research on spatial and energetic characteristics of the ion beams emitted in the PF - 360 discharges

Experimental results are presented on the spatial structure and energetic characteristics of the fast ion beams produced by high-current discharges in a PF-360 device operated at the National Centre for Nuclear Research (NCBJ, Otwock/Świerk, Poland). The 105 kJ discharges were initiated at the initial deuterium pressure around p0 = 6 hPa and were powered from a 234 miF capacitor bank charged up to 30 kV. The spatial structure of the ion beams was recorded using pinhole cameras equipped with the solid-state nuclear track detectors of the PM-355 type, placed at two different angles (0 centigrade, 45 centigrade) relative to the discharge axis. The detectors were shielded by thin absorption filters made of pure Al foils of various thickness, which made it possible to record only ions with energies exceeding a chosen threshold value. Similarly as in other plasma focus (PF) experiments, energies of the emitted ions ranged from about 30 keV to about 3 MeV, i.e. they were much higher than the voltage applied to the electrodes. The recorded ion images showed a complex spatial structure of the fast ion beams, which consisted of many micro-beams of different energies. It is possible that these beams were emitted by various local micro-sources (e.g. plasma micro-diodes) the were formed inside the PF pinch column.