Generation of sub-GW RF pulses in nonlinear transmission lines

The paper presents the results of recent experiments on the generation of subgigawatt RF pulses using two types of nonlinear transmission lines (NLTL´s). In the high-voltage coaxial lines, we used: (1) periodic gas gap structure and (2) uniformly loaded saturated ferrite with axial bias. The concept of the first element is based on the in-phase composition of RF fields produced by currents in the periodic gas gap structure of the inner conductor. The most stable and efficient narrow-band operation of the system with 12 cylindrical gas gaps (200 kV, 18 ns) was realized at a radio frequency of 1 GHz and an RF power of several hundreds of megawatt. The maximum efficiency of power conversion was 10%. The bandwidth was about 10 % at a -3 db level. The second NLTL lacked spatial dispersion and self-consistent dynamics of the traveling wave was observed in the coherent magnetic switching in ferrites with axial bias. The pulsed voltage driver produced 9-ns pulses of voltage between 110 and 290 kV. With the optimum external magnetic field, the efficiency of energy conversion for the first eight oscillations was ~10%. The peak power of oscillations produced on a resistive load was ~400 MW. A linear increase in central frequency from 600 MHz to 1.1 GHz with incident pulse amplitude was found.