A magnetically insulated transmission line oscillator working at HEM11 mode

A novel magnetically insulated transmission line oscillator (MILO) which takes HEM₁₁ mode as its main interaction mode is put forward for the first time in this paper. The excitation of HEM₁₁ mode is made possible by carefully adjusting the structure parameters of each resonant cavity. The high frequency characteristics are analyzed. The special feature of such a device is that, in the slow-wave-structure (SWS) region, the interaction mode is HEM₁₁ mode which is a TM-like one that could interact with electron beams effectively; and in the coaxial output region, the microwave mode is TE₁₁ mode which has a favorable field density pattern to be directly radiated. An experiment is carried out on the HEM₁₁ mode MILO and the detailed experiment results are discussed in this paper. Employing an electron beam of about 480 kV and 39 kA, HEM₁₁ mode MILO generates a high power microwave output of about 1.2 GW with 40 ns pulse duration at 1.98 GHz. The power conversion efficiency is about 6.5% and the generated microwave mode is TE₁₁ mode.