Research On The PIC Simulation Of POS Operation In External Magnetic Field And The Experimental System

Plasma opening switch (POS) has good advantages of inducting large current, opening circuits fast and generating high voltage. It has become one of the critical components in inductive energy storage pulsed power technique. To enhance the energy transmission efficiency and increase the voltage and power multiplication in opening process, it is especially important to pay more attention to improving the opening characteristics of POS. Adding assistant magnetic field can bring great benefits. The effects are demonstrated in: the increase of magnetomotive force will promote the magnetic insulation of emission electronics in cathode. Limiting the distribution of plasma particles can make the particles easier to be cleared in opening process and then the POS can open the circuits thoroughly. The thesis is aimed to investigate the internal complex physical phenomena and principles of POS when adding the assistant magnetic field and search for effective ways and develop techniques to improve the opening characteristics. Based on the theoretical analysis, the plasma generation source and POS inductive energy storage pulsed power system was designed and the relative experiments were carried out.The dissertation firstly summarized the general situations and representative studies of POS techniques in and out of China, including the physical principles in opening process and the experimental studies in recent 30 years. The characteristics and working states of POS are mainly determined by the factors including geometrical shapes of electrodes, the density and distribution of plasma, the strength of conducting current, conducting period and adding magnetic fields etc. Therefore, the development stages of POS were reviewed through different categories of electrode geometrical shapes combining other factors. The summary and review work can provide references for experimental device design and optimization.To investigate effect of external quasi-axial magnetic field on the opening characteristic of the coaxial POS, particle-in-cell (PIC) method was applied to simulate the operation characteristics of the coaxial POS with inner cathode in external quasi-axial magnetic field. The opening process was simulated in two conditions, the excited magnetic coils placed inside the cathode and outside the anode respectively. The space-time changing of electric and magnetic field and the kinetic behaviors of plasma electrons in POS have been analyzed from the views of obtaining higher opening voltage, less current loss, greater opening efficiency etc. The key is the opening process of POS with inner cathode. Based on the simulation results, symmetrically, we can conclude that for coaxial POS with extra anode, the excited coils of quasi-axial magnetic field should be placed outside of extra anode so that the opening process can be accelerated and higher opening voltage, greater current transmitting efficiency and lower current loss can be obtained.To study the opening process of coaxial POS affected by the external added azimuthal magnetic field, PIC method was also applied. The complex physical phenomena in opening process of POS were analyzed completely. The studying points included the azimuthal magnetic field distribution between electrodes, penetration of magnetic field, the distortion of electric field and its effect, spatial distribution of particles, characteristics of particle beams and the spatial distribution of electrons beams etc. It can be concluded that the electronics drifted to the load side clearly from the electronic spatial distributions; the plasma magnetic pressure was enhanced by the external added azimuthal magnetic field in the turn-on period, and the switching voltage was multiplied.Based on the above theoretical analysis, an integrated system with flashbard plasma gun, coaxial POS excitation source and diagnostic parts is designed. Some key parameters, including switching geometric parameters and material parameters, are proposed in structural design. The POS experimental device was used for investigating experiments. The performances of the POS inductive energy storage pulsed power system were estimated and some application studies were carried out.The results of theoretical and experimental research presented in this dissertation are useful for the design and establishment of higher current facilities based on inductive energy storage technology.