Numerical Analysis Of Pre-charge And Turn-on Process And Voltage Measurement Of RSD

The fundamental concept of pulse power technology and the advantages and disadvantages of traditional switch devices and semiconductor switch devices used in pulsed power system were introduced first. RSD is a novel kind of pulsed power devices based on controllable plasma layer. Compared with traditional semiconductor devices, RSD has characteristics of high forward blocking voltage, great peak current, high di/dt, long lifetime and high repetitive rate et al, which lead to RSD's great prospects in pulsed power system. Accurate measurement and modeling analysis are needed to get a clear picture of the mechanisms of RSD and to direct design for higher performance.RSD is one kind of pnpn device with short points at both of cathode and anode. The basic principle of RSD is introduced, and the working process was analyzed. Based on semiconductor theory, Grekhov model and the improved model were also introduced. Analytic expressions of distribution of plasma,electric field and voltage were deduced during both pre-charge and turn-on process.The problem of traditional measurement of voltage waveform was analyzed. Two methods, decrease voltage with serial devices and multiply current with parallel circuit, were designed. Relatively accurate waveforms were measured by experiment devised with RSDs in series. The reliability of the method was proved by the consistent of measurement results in conditions of different voltage ration.Based on the full set of semiconductor device equations, a 2-dimension numerical model of RSD was set up in a cell structure with finite difference method. Included in the model were the physical mechanisms such as carrier-carrier scattering, SRH and Auger recombination, impact ionization and so on. Besides, Circuit model triggered by resonant method was built upon the parameters extracted from experiment conditions. Together with the circuit model, the devices model was calculated by program written in MatLab with Runge-Kutta and Newton iterative method to get the distribution of carries and the waveform of current and voltage. Based on the comparison between the result of calculation and experiment, validity of the model was analyzed and explanation of error was given. The pre-charge process was also analyzed with the help of concentrations of n, p and current density derived from the simulation. Significant Auger recombination and withdraw current during the pre-charge process diminished the quantity of plasma injected by the pre-charge current, which demonstrate that the current integral during the pre-charge process can not represent the whole quantity of pre-charge. During the turn-on process, the carriers in p-base region decreased a lot and the re-injection of carriers from cathode was much slower than that from anode, so it's reasonable to believe the structure of cathode played a much more important role in the trun-on process. Those results could be used to direct the design and application of RSD.