Approaches to achieving high efficiency, long pulse, vacuum backward wave oscillator operation

This paper describes recent achievements in the study of short pulse (10s of nanoseconds) high power backward wave oscillators (BWOS) and the difficulties associated with applying these results to long pulse (100s of nanoseconds) microwave generation. Finite length effects observed in the short pulse studies were reproduced in electromagnetic particle-in-cell simulations. These results motivated the incorporation of concepts from control theory to design a frequency agile BWO. High temporal and spatial resolution plasma diagnostics will be installed on the long pulse experiment to assess the effects of plasma on pulse shortening.