Axial Distribution Profile of Magnetic Field and Plasma Sheath Velocity in Argon Plasma Focus Device

Abstract

The main aim of this work is to study dynamics of plasma current sheath, PCS during the axial acceleration phase in term of its axial velocity, V_z and the induced azimuthal magnetic field induction, B_θ in 2.2 KJ plasma focus, PF device of Mather type. It powered by a capacitor bank of 30 µf capacity with charging voltage of 12 KV. In the present paper all the experimental work are performed for Argon gas pressure in the range of 0.2 1.8 Torr. The length of the inner electrode, IE has been changed to 9.5, 10.5 and 11.5 cm respectively. To detect, B_θ and V_z three identical magnetic probes are located at radial distance r₁ = 2.75 cm, r₂ = 3.5 cm and r₃ = 4.25 cm from the IE axis and at axial distance z = 8.15 cm from coaxial electrodes breech.The dependence of V_z and B_θ on gas pressures are measured and the results of them clear that, V_z is decayed with increasing of gas pressures and it has a maximum value for IE length of 10.5 cm, P = 0.2 Torr and at r₁, while B_θ has a maximum value for IE length = 11.5 cm, 1.2 Torr at r₁ . Also distribution of V_z with p in linear fitting shows that efficient a snow-plough action is obtained approximately for IE length = 10.5 cm. Results of V_z versus radial distance demonstrated that the PCS has a parabolic shape especially at lower Argon gas pressures. Results of modification factor, F as a function of gas pressures show that at IE = 10.5 cm, r₁ and for most Argon gas pressures F has a higher values than any others IE lengths and radial distances. Also the decay of dF/dp along radial distances has a smaller values at IE length = 11.5 cm than any other lengths (9.5 and 10.5 cm).