Particle beams and current distribution in 5-25 kJ PF machines

The current distribution in the interelectrode gap of plasma focus machines (PF) is modified via controlled (as opposed to random) processes, affecting distribution lumpishness and multiplicity of plasma current sheath (CS) between electrodes. Magnetic probes, schlieren, image converter photography and particle emission from the pinch provide basic quantitative information from each discharge. CS characteristic parameters are recorded simultaneously with ion beam fluence from PF machines of different powering energy values V, 5 kJ ≲ W ≲ 25 kJ. A correlation analysis for variations of W, CS parameters and beam fluence is carried out with the objective of determining general scaling laws. Current patterns of minimum inductance in the plasma compete with current patterns of maximum efficiency for magnetically compressing energy in the pinch. The desirable latter patterns are favored by using suitable field distortion elements, which also increase the fast ion emission in all discharges with a "medium" value (as opposed to extremely-high or extremely-low values) of the neutron yield from D-D fusion reactions.