| Electromagnetically-driven high energy density physics (HEDP) is a fast developing frontier of modern science. High power electric pulses with current of 100～101 MA and power of 101～102 TW are transmitted to load in centimeter dimension, achieving the high energy density conditions for inertial confinement fusion (ICF), equation of state, nuclear weapon physics and other HEDP investigations. Due to small load dimension and the induced high power density (up to 1012 W/cm2), vacuum magnetically insulated transmission line (MITL) is inevitable for high power pulse transmission.The characteristics of MITL are relevant to the voltage, current, line impedance and load impedance. The relationships between them had been studied widely in the past decades, which supported the construction of a series of high power pulse facilities. With the increasing of power density, the mechanism which influences MITL characteristics becomes much more complex. The energy loss to electrode increases evidently, and then the resulted ion emission, electrode plasma forming and expansion cannot be ignored. More importantly, the electrode with current density up to MA/cm will be physically damaged in one shot. Whether the electrode can withstand enough time to make energy transmit to load before its disruption is the bottleneck of feasibility. Therefore, the investigations on the relationship of current rise time and MITL characteristics are critical important.This dissertation pays special attentions to the influence of current rise time to characteristics of multi-level MITL system. Special emphasis is on the rise time of a few hundreds of nanosecond, which has not been thoroughly studied so far. Current loss in the outer MITL during the establishment of magnetic insulation, loss in the post-hole convolute (PHC) area after the establishment of magnetic insulation and energy loss to conductor with current density above MA/cm in inner MITL are investigated. According to theoretical analysis and numerical simulations, the dissertation tries to establish connections between measurable parameters (i.e. current, voltage and rise time) and un-measurable parameters (for example current loss and energy deposition to anode, temperature and current density distribution in electrode). These works help us to better understand the magnetic insulation problem, and also promote the ability in numerical simulations, which we hope to be helpful for future investigations. The main achievements and conclusions of this thesis are as follow:(1). A Full-circuit Analysis and Simulation Tool (FAST), which takes current loss during the establishment of magnetic insulation into consideration, was developed for the Primary Test Stand (PTS) facility. The code reliability was validated with Pspice and experimental result. The FAST code gives a new tool for experiment design, performance prediction and results analysis with higher efficiency. The tool also makes it possible to analyze MITL characteristics in different rise time.(2). Current loss in outer MITL during the establishment of magnetic insulation and current loss in the PHC area after the establishment of magnetic insulation was analyzed for two types of experiment on the PTS, in which fast and slow current rise time are covered. It shows that, for z-pinch experiment with faster rise time, and higher load impedance, more current is lost to anode. And for magnetically driven isentropic compression, less current is lost due to slower rise time. However, the trends for current loss in the outer MITL are the same for different rise time.(3). The mechanism for energy loss to conductor in inner MITL was studied, where current density is up to MA/cm. A1D magneto-hydrodynamic (MHD) code for magnetic field diffusion and resulted plasma generation on electrode surface was developed. The influence of current rise time to energy deposition was numerically investigated. The result indicates that, for given current density, energy deposition is nearly proportional to current rise time. In order to mitigate magnetic diffusion into conductor and energy deposition to conductor, slower current rise time is beneficial. However, this will introduced higher voltage to MITL.
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