Circuit Simulation of the MITL in an IVA with a Non-Ideal Center Conductor

Abstract

The present MITL (magnetically-insulated transmission line) center conductor of the Mercury IVA (inductive voltage adder) tapers down in diameter at each cell feed so as to have the ideal, uniformly increasing steps in impedance as the line voltage increases. This provides optimal power coupling to a self-limited load and ensures that electron flow will not be lost at the impedance transitions of the MITL, thereby retaining magnetic insulation. The output voltage of Mercury into a self-limited load can be increased by decreasing the diameter of the center conductor, increasing the MITL impedance. A simple, low-cost way to do this is to reuse some small segments of the existing center conductor, even though they have non-ideal diameters in this new configuration, and add a few, smaller diameter components. However, impedance mismatches and current loss down the MITL can reduce the output voltage in this non-ideal case. So, simulations were required to verily that the new MITL would still be magnetically insulated and efficiently couple power to the load. A new MITL circuit element that has a variable impedance and that can model current loss at non-ideal impedance transitions was used in a transmission-line circuit code to quickly evaluate possible combinations of new and existing center conductor elements. In two MITL configurations tested, insulation (or the loss thereof) and power coupling predicted in the circuit code was verified by PIC (particle-in-cell) simulations using LSP, So, with the aid of a transmission-line circuit model that includes a new MITL circuit element, a simple, low cost modification to the existing Mercury MITL center conductor that increases the output voltage has been designed.