Dynamics of Hot Spots Formation in a Dense Plasma Focus Optical and X‐ray Observations

Hot spots are dense plasma formations emitting strongly in the medium to hard X‐ray regions. Their presence can be detected in a dense plasma focus when high Z impurities are added to the main gas of hydrogen or deuterium. Experiments have been carried out on DPF 78, a medium size, 28 kJ, 60 kV Mather type Plasma Focus operating with heavy gas admixtures to the hydrogen or deuterium fill gas. Using a range of time and space resolved diagnostics in the optical and X‐ray region, the dynamics and properties of hot spots were investigated. The complementary nature of these diagnostics working in conjunction allowed us to construct a physical description on the evolution of these dense plasma formations. The first appearance of hot spots was detected within 5 ns of first compression, at a time when the bulk of the plasma column is grossly stable. However this gross stability coexists with strong local density gradients as observed in Schlieren photographs which are correlated to the hot spots. The existence of...