3D Particle-in-Cell Modeling of the Saturn Post-Hole Convolute

Summary form only given. Most of the previous convolute simulations have used either short-circuit or Z-pinch loads. For Z-pinch loads the impedance starts as a short circuit and rises near the peak of the X-ray signal as the Z-pinch collapses causing a rapid change in the inductance. Electron-beam-diode loads are currently being developed for the Saturn machine located at Sandia National Laboratories. The impedance history for an electron beam diode is quite different than a Z-pinch. The impedance history of the diode can lead to dramatically higher flow currents in the magnetically insulated transmission lines (MITL´s) and produce higher electron losses in the convolutes. These enhanced losses can cause plasmas to short out the convolutes leading to a substantial loss of usable power at the load. The diode impedance is initially very high during the time when electron and ion emission thresholds are being met and electrode plasmas are being formed. It is during this critical time when the voltage is high and the current is low that substantial losses can occur. In recent experiments, it was shown that a plasma-filled diode (PFD) substantially improved the power delivered to an electron beam diode load on Saturn. In a PFD, the diode impedance is initially a short circuit which then rises to a finite value as the current pulse redistributes the plasma. The impedance history of the PFD has many potential advantages over the vacuum diode. The early-time power-flow through the convolutes should improve with a PFD since the current is initially high and the voltage is low. The three-dimensional particle-in-cell code, LSP, is being used to study the effect of the load-impedance history on power-flow through the Saturn convolutes. Available simulation results will be discussed