Power Flow in a Magnetically Insulated Recyclable Transmission Line for a Z-Pinch-Driven Inertial-Confinement-Fusion Energy System

Power flow in a recyclable transmission line (RTL) for a z-pinch-driven inertial-confinement fusion energy (IFE) system is studied. In a magnetically insulated transmission line, plasma forms by explosive emission on the cathode but emission from the anode does not occur. However, in an RTL, the large linear current density that flows in the electrodes at small radius near the load resistively heats the anode surface, leading to anode plasma formation and ion emission. If the impedance of the RTL is too small, large ion current losses can occur and large electron flow currents can be launched into the z-pinch load region. If only the boundary current drives the z-pinch load, then these large electron flow currents can introduce a polarity effect with more bound current in the anode than the cathode. While being mindful of the IFE system requirement to maintain a small RTL inductance, these problems are avoided by choosing the line impedance at the load end of the RTL to be well above the effective impedance of the imploding load. In this case, the ion current losses are tolerable and the electron flow current is negligibly small. For the present baseline design with a peak current of 60 MA driving a 100-ns implosion, these power flow constraints require a gap of order 2 mm or more at the load end of the RTL