الفهرس 
INTRODUCTION .Only 14 pages are availabe for public view
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Abstract
Recently, interest has been shown in using the plasma focus (PF) device as pulsed soft x-ray source for x-ray spectroscopy, x-ray cinematography, laser pumping, and high-density microelectronic lithography. It also could be used as a portable neutron source, as a source of energetic ions for nanofabrication and as testbeds for the study of neutron and x-ray generation as well as studies of high energy and density physics. A great deal of numerical research has been done into the mathematical models of dense plasma focus (DPF) devices to describe their behavior during different time phases. One of the most authenticated models for single pinch Mather-type devices is the six phases model invented by Lee. The main objectives of this thesis are firstly improving and refining Lee model for conventional single pinch DPF devices through studying the effect of breakdown phase and current sheath (CS) inclination during the axial phase on the current drive factor (𝑓𝑐 ) of Lee model, which is used to fit the greater calculated current to the lower measured one. This effect has been proved using a 2-D model that considers the breakdown phase and the thickness of the CS. The modulation and refinement of the parameter will be shown. The movement, shaping and thickness of the two-dimensional plasma sheath will also be presented. Secondly, A generalized model for the multistage sequential plasma focus has been developed and used. This model is derived from Lee model, where the phases are adapted to describe several plasma current sheaths (PCS) that produce consequence focus events. The model simulates the performance of such devices by cyclic five phases to consider all the states of the formed current sheaths. Comparison shows a remarkable agreement of the measured current with that computed from the multistage model code in the case of dual stage pinch PF. Using the model, the sequential focus events could be optimized, and the effective parameters could be investigated.