Effect of ion emission on power flow in an MITL feeding a Z-pinch load

Summary form only given. Power from the Z machine at Sandia National Laboratories is delivered to the Z-pinch load via a magnetically insulated transmission line (MITL). The electric field stresses on the cathode of the MITL exceed the turn-on threshold and cause electron emission; however, electrons are magnetically insulated from the anode due to the high currents. As long as the anode does not emit ions, the MITL can be confidently designed to efficiently deliver power to the load. However, high current density can resistively heat the anode to a sufficient temperature so that gas is desorbed, which can then ionize to form an anode plasma. In fact, near the load where the power converges to small radius, the heating can be so severe that surface melting can occur. In this work, the effects of ion emission from anode plasma on power flow are considered. Ion emission over a significant length of the MITL could result in large current losses if the anode-cathode gap in the MITL is small and the ions are not magnetically insulated. Analytic theory was developed and PIC simulations were performed to evaluate the power flow efficiency in this environment. Available results are presented and implications for Z and future systems are discussed. In particular, the impact of extending this architecture to a Z-pinch-driven inertial fusion energy power plant is considered