The 6th International Conference on Matter and Radiation at Extremes (ICMRE2023)

112 / 2023-04-13 22:20:44

On the design of magnetically insulated transmission line for China next generation pulsed power machine

Inertial Confinement Fusion Physics > Alternative ICF and pulsed power technology-I

We describe the design of magnetically insulated transmission line (MITL) system by circuit simulation for China next generation pulsed power machine. This facility can produce a maximum current over 50 MA with a rise time less than 150 ns. It mainly consists of 3600 LTD cavities, 72 water-insulated transmission-line impedance transformers, 144 bi-plate transmission-line impedance transformers, an insulation stack of six-layer, and an MITL system. The MITL system is composed of six-level outer MITLs, triple post-hole convolute, and inner MITL. The outer diameter and height of the entire system are about 5.5 m and 6.8 m, respectively. It combines and transmits the currents from the upstream LTD cavities to the target. A circuit model including the insulation stack, vacuum flare, and MITL is proposed. The circuit model of the MITL section has incorporated the following processes: explosive electron emission, current loss prior to magnetic insulation, electron current flow after the establishment of magnetic insulation, electrode temperature increasing due to joule heating and electron-energy deposition, generation of plasmas on anode and cathode electrodes and their effects on the vacuum impedances of MITLs, the electron flow currents lost at the TPHC region. The whole circuit model contains more than 2000 transmission line elements and the time step of circuit simulation is about 0.04 ns. The electron loss currents occurring within the outer MITL and TPHC regions are obtained. Finally, particle-in-cell (PIC) simulation is also performed to check the exactness of circuit simulation results. Although circuit and PIC simulations are performed which could model the behavior of electrons accurately, the plasmas forming with the TPHC and inner MITL regions will strongly degrade the current transmission efficiency, especially for the load with high inductance. This mechanism will decrease the amplitude of the load current evidently. This will be subject to future work.