Design Analysis and Simulation Investigation of S-band MILO

Abstract

The Magnetic Insulated Line Oscillator (MILO) has gained popularity in recent decades as a useful high-power microwave device, due to its inherent property of self-insulating magnetic field. The self-generated magnetic field acts as an internal insulation barrier within the device and prevents electrical breakdown, which is important for gigawatt range operation. S-band MILO design, analysis, simulation and parameter optimization has been studied and presented in this paper. The presented MILO design consists of a three-stage choke cavity, three- cavity extraction region, and a slow wave structure. An attempt is made to increase the efficiency by using the concept of a tapered extraction region which improves wave extraction at the output a beam dump disk which acts as a tool to properly utilize the load current for self-insulating magnetic field generation. The disk is supported by four appropriately sized and positioned stubs for impedance matching, and hence improve output power. A parametric optimization run on both the structural and beam parameters provides the best values for operation. The results presented are obtained using the commercial software CST Studio, using its 3D Particle-In-Cell (PIC) simulation method. Eigenmode analysis is also performed on the slow wave structure to get dispersion curves for resonant frequency of MILO and verify its operation in n-mode. Simulation results reveal that the S-band MILO generates dominant TM01 mode at the desired frequency of 3.4 GHz. The results show a stable frequency response throughout the time of operation, as well as a high dominant mode efficiency of 98%. The generated wave has a peak power of 6.8 GW and a peak efficiency of 22.5% with the application of an input pulse voltage of 530kV and 57kA current.