High Power Microwave Sources design and experiments

Abstract: High-Power Microwaves (HPM) can be used to intentionally disturb or destroy electronic equipment at a distance by inducing high voltages and currents. This thesis presents results from experiments with a narrow band HPM source, the vircator. The high voltages needed to generate HPM puts the vircator under great stress, especially the electrode materials. Several electrode materials have been tested for endurance and their influence on the characteristics of the microwave pulse. With the proper materials the shot-to-shot variations are small and the geometry can be optimized in terms of e.g. output power or frequency content. Experiments with a resonant cavity added to the vircator geometry showed that with proper tuning of the cavity, the frequency content of the microwave radiation is very narrow banded and the highest radiated fields are registred. Since HPM pulses are very short and have high field strengths, special field probes are needed. An HPM pulse may shift in frequency during the pulse so it is very important to be able to compensate for the frequency dependence of the entire measurement system. The development and use of a far-field measurement system is described.