Pinched Plasma Study in a Filippov-Type Plasma Focus “Dena”

A characteristic feature of physical processes occurring in pinched plasma is their tendency to generate thermal and nonthermal emissions. In this case, the roles played by plasma compression dynamics such as pinch formation, pinch disruption, expansion, etc., are predominant. In this paper, first, we present some of the experimental results concerning the thermal and nonthermal neutron emissions. Then, a new approach based on some theoretical assumptions and the experimental data for which the pinched plasma density evolution was studied are introduced. In the new approach, the compression dynamics are divided into two phases: plasma compression (thermal) and plasma expansion (nonthermal). For each phase, electron distribution functions such as a parabolic and a hyperbolic are attributed, respectively. Assuming a maximum electron density for each phase and an Abel integral equation (used in laser interferometry method), the fringe density maps in a new Filippov-type plasma focus “Dena” (25 kV, 288 $\mu\hbox{F}$, and 90 kJ) operating in deuterium gas were obtained in the approximation of low collision frequencies.