The effect of helium impurity addition on current sheath speed in argon-operated plasma focus using a tridimensional magnetic probe

Abstract

Using the tridimensional magnetic probe, the current sheath velocity at 0.25 Torr is studied in Sahand, a Filippov-type plasma focus facility. The current sheath velocity in argon-filled plasma focus with different percentages of helium impurity at different operating voltages was studied. The highest average current sheath velocity of 12.26 ± 1.51 cm μs −1 at the top of the anode in the axial phase was achieved at 17 kV. Minimum average current sheath velocity is 5.24 ± 1.18 cm μs −1 at 12 kV with 80% argon + 20% helium as a working gas. The full width at half-maximum of peaks of the magnetic probe was found to be inversely related to the current sheath velocity, i.e. smaller at higher voltages for different impurity and decreased with increasing of impurity.