Drive parameter as a design consideration for mather and filippov types of plasma focus

Abstract

Summary form only given. The operating conditions of the plasma focus depend strongly on several macroscopic parameters like energy of cap bank, current, voltage, electrodes dimension, and curvature of current sheath in axial phase. The drive parameter (Ip/a)/radicrho which is proportional to the speed of the plasma in both axial and radial phases is one of the most important parameter which determines the performance of a DPF as a source of fusion neutron. Experiments on 2-3 kJ DPF have been done to show that this parameter is important over a wide range of other parameters like anode length, insulator sleeve length and operating gas pressures. The NX2 machine was modified to have different aspect ratios ranging from A = L/2a ap 0.2 (NX2-F) to 1.52 (NX2). Here 2a, the diameter of the anode is taken from the flat top of the anode and L is taken as the free length of the anode, i.e. between the tip of anode to the insulator sleeve. In the case of neutron yield the speed is critical as the highest temperature ~1 keV needs to be achieved as the cross section is strongly dependent on temperature. A between high speed which implies high and low speeds which implies longer time gives the optimum yield for drive parameter 89 kA/cm/torr1/2 for Mather type focus and a drive parameter of 50 kA/cm/torr1/2 for Filippov type focus. The NX2-F with its mushroom shaped anode has a drive parameter intermediate between the Filippov and Mather type plasma focus is due to the shape intermediate between the Filippov and Mather type plasma focus devices. The drive parameter for NX2-F is found to keep constant at different voltages. In addition, neutron yields from the modified plasma focus tube without original cathode rods were also found to have the same order magnitude as the original electrode systems and reach the highest at the same gas pressure. This confirms that the drive parameter has an importance over cathodes at a big range of gas pressures