Coaxial–Conical Transition in Magnetically Insulated Transmission Line

Coaxial magnetically insulated transmission line (MITL) was widely used in high-current pulsed power facilities. It is also an important option in future high-current accelerators based on the linear transformer driver (LTD) technology, in which the output line is usually coaxial to fit the component layout. In one of the schemes for high-current LTD accelerator, tens of coaxial MITLs are connected to conical disk lines in parallel. As a special structure, the coaxial-conical transition is a key component of the system. The feasibility of efficient current transmission under magnetic insulation condition is the precondition for building such a pulsed power facility. In this paper, we report the results of coaxial-conical MITL transition experiment which were conducted on the primary test stand (PTS). At the inner MITL of PTS, four coaxial MITLs were connected, gradually changed to mini-triplate and finally connected two conical MITLs. The total current at the entrance of coaxial lines (input) and at the conical MITL (output) were recorded. It showed that an output-to-input current efficiency of above 96% and of 87% across the transition was achieved with short load connection and open load connection, respectively. The 3-D transient electromagnetic simulation and 3-D particle-in-cell simulations were conducted to check the transmission efficiency, which confirmed very tiny loss when the load was short connected.