Plasma Current Sheath Dynamics and Energy Dissipation in a Low-Energy Plasma Focus Device

Abstract

This paper reports the measurements of plasma current sheath (PCS) dynamics, the energy dissipation processes, and the plasma focus (PF) electrical characteristics, particularly during the axial phase discharge in a Mather-type PF device (EAEA-PF1) energized with a 30 µF capacitor bank charged with 8, 10 and 12 kV. All these works are carried out under discharge conditions where the optimal PF action is achieved. At each charging voltage (Vch), 8 kV, 10 kV and 12 kV, the optimal PF action is studied for different Argon gas pressures (P) ranging from 0.4 to 1.2 Torr. The results show that the best PF is formed at Vch = 8 kV and P = 0.6 Torr, Vch = 10 kV and P = 0.8 Torr, and Vch = 12 kV and P = 0.8 Torr. The implosion velocity (Vz) results of PCS show that the maximum value of Vz (4.48 cm/µs) occurs at the end of the axial phase (i.e., at the coaxial electrode muzzle), which is detected at Vch = 12 kV and P = 0.8 Torr. Moreover, a less inefficient snowplow action is observed under these discharge conditions. The energy dissipation process data indicate that at Vch = 12 kV and P = 0.8 Torr, the ratio between the total energy dissipation and the input energy has a maximum value of ≅ 90%, and the minimum residual energy left on the condenser bank (175.39 J) is also achieved under these discharge conditions.