Study of DPF working with high density neutral gas concentrated in the focus zone

In the dense plasma focus (DPF) PACO (2 kJ, 31 kV, 250 kA in the focus) operated with D2, the gas density in the focus region is locally increased, before the electrical discharge, by the injection of a subsonic gas jet. This gas density profile is theoretically predicted, and it is experimentally checked with schlieren photographs of the jet and by temporal resolved measurements of density with a fast probe. The timing of the electrical discharge respect to the density evolution is experimentally adjusted to obtain the maximum D-D neutron yield. A systematic study shows a sensitive improvement of the average neutron yield respect to the operation with uniform gas filling pressure. (author)