Pulse shortening in high-power backward wave oscillators

Chris Grabowski; John Michel Gahl; Edl Schamiloglu; Charles B. Fleddermann

doi:10.1117/12.255386

28 October 1996 Pulse shortening in high-power backward wave oscillators

Chris Grabowski, John Michel Gahl, Edl Schamiloglu, Charles B. Fleddermann

Proceedings Volume 2843, Intense Microwave Pulses IV; (1996) https://doi.org/10.1117/12.255386
Event: SPIE's 1996 International Symposium on Optical Science, Engineering, and Instrumentation, 1996, Denver, CO, United States

Abstract

Pulse shortening is a phenomenon common to all high-power microwave devices. Whereas in electron beam driven sources the electron beam propagation in the device may be for several microseconds or more, the microwave pulse duration is typically no greater than approximately 100 ns. Specific reasons for pulse shortening may vary among devices, but all explanation of the phenomenon put forth involve the introduction of plasma into the interaction region near the walls and/or the degradation of the beam quality. To gain a better understanding of pulse shortening in high power backward wave oscillators (BWO's), an investigation is being conducted at the University of New Mexico (UNM) on the UNM Long-Pulse BWO Experiment. Recent experiments have involved monitoring the beam current in the slow-wave structure (SWS) at different radii as a function of time. The current waveforms are correlated with the time histories of microwave pulses measured in separate experiments. The results reveal the appearance of electrons between SWS ripples at times corresponding to when the microwave signal peaks. A drop in the main beam current is observed shortly thereafter. Coatings of TiO₂ and Cr have been placed on the inner surface of the SWS in an effort to suppress electron emission. Initial results with the TiO₂ coatings have shown a measurable increase in microwave pulse width.

Citation Download Citation

Chris Grabowski, John Michel Gahl, Edl Schamiloglu, and Charles B. Fleddermann "Pulse shortening in high-power backward wave oscillators", Proc. SPIE 2843, Intense Microwave Pulses IV, (28 October 1996); https://doi.org/10.1117/12.255386

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