Research On A Wave Erection Marx Generator And Its Applications

Driven by national defense and industrial applications, pulsed power technology has been advancing towards higher average power and more compact structure. A wave erection Marx generator is one of the important candidates for these development trends. It has been well developed by foreign researchers, whereas domestic reports have not been found yet in literature. In this dissertation, a 10-stage wave erection Marx generator is developed based on detailed theoretical analysis, total circuit simulations and experimental design. Preliminary researches are also made on its potential applications and repetitive operation characteristics. These efforts are instructive for the further development of this kind of pulse generator, and also set a good foundation for the realization of higher performance as well as more extensive applications.This dissertation mainly consists of the following aspects.The wave erection Marx generator is investigated theoretically in detail. Through the analysis of the factors influencing the amplitude of over voltage across gas spark gap in a single stage, it is found that eliminating the coupling stray capacitance between stages and increasing the stray capacitance between the electrode and the ground are favorable for the formation of erected waveform of the Marx generator. Equations describing the equivalent discharging circuit of an N-stage wave erection Marx generator are established and numerically calculated. The results show that under the specific structure parameters of the single stage, the generator has an optimum number of stages to obtain an output pulse with both a fast rise time and a quasi-square waveform. Considering the impedance and the charging uniformity synthetically, the optimum number of stages is chosen to be 10 at last. The effects of parameters on performance of the 10-stage wave erection Marx generator are analyzed. The analysis results show that the single stage circuit inductance slightly affects the variation trend of output voltage waveforms, however a larger inductance will reduce the pulse amplitude, and increase both the pulse width and the rise time; while the stray capacitance between the electrode and the ground is the critical component and it should be of a proper value to form a high voltage pulse with fast rise time on the load. Calculation results also show that the switch-closing in order is very important for the wave erection process. A total circuit model of the 10-stage wave erection Marx generator is developed via PSpice software and detailed simulations are performed based on the model. The simulation results agree well with the above calculation results.Based on the theoretical analysis results, a resistively isolated 10-stage wave erection Marx generator is designed and constructed with 3 nF high voltage low inductance capacitors and 50 k? high power solid resistors, respectively, as its energy storage and isolation components. The dimension of this generator isΦ0.22 m×1.6 m. At a 40 kV charging voltage, the generator can deliver a high voltage pulse with amplitude of ~210 kV, rise time of ~5 ns, and pulse width (FWHM) of ~40 ns to the 90Ωmetal film resistor load. It is the first domestic report on this type of pulse generator with such performance. Through experiments it is found that a coaxial structure is important for both the design and the diagnostics of the wave erection Marx generator. Due to proper design with respect to the over voltage across spark gap to realize the spark gaps closing rapidly in order, the generator can produce a fast rise time and high voltage pulse even without the help of ultraviolet (UV) coupling between stages; however its performance may be enhanced with UV coupling introduced by further modification of the generator structure. Compared to the copper sulphate solution load, the metal film resistor load combines such two virtues that nearly without stray capacitance and adopting an impedance tapering structure to reduce wave reflection, thus it can make a more precise measurement in cooperation with a capacitive divider. The output performance of the generator has been analyzed through defining two kinds of impedances, Z0, the lumped impedance of the generator, and ZN, the impedance raised from the effective transmission line formed by stray parameters of the generator. Then a further improvement suggestion of the generator is put forward.Preliminary research is made on the application of the 10-stage wave erection Marx generator. When applied as a high voltage trigger, it is found to be suitable for triggering the systems where strict synchronization is required. The generator is successfully utilized to drive a field-emission diode directly, which accomplishes the joint function of a transformer and a pulse forming line (PFL) and verifies the possibility to drive an intense relativistic electron beam (REB) accelerator. This result indicates that the wave erection Marx generator driven REB accelerator may open a new economical and reliable route for the minimization of the REB generators. The 10-stage wave erection Marx generator is also found to be applicable for producing ns range underwater shockwave to simulate the electric water hammer effect of the water transmission line based REB generator in operation. The energy transformation rate of electrical pulse and shockwave is obtained under certain conditions. All the above applications show that the wave erection Marx generator has a promising future.The 10-stage wave erection Marx generator is modified from a resistively isolated configuration to an inductively isolated configuration for the investigation on its repetitive operation characteristics. The experimental results show that at a 30 kV charging voltage, the 10-stage wave erection Marx generator can operate stably at 8.2 Hz repetition rate without gas blow-off from the internal spark gaps, producing an output pulse of 150 kV and 1.8 kA.