Recent results in the hard-tube MILO experiment

Summary form only given. The Hard-Tube MILO (Magnetically Insulated transmission Line Oscillator) is a gigawatt-class high-power microwave tube which employs conventional tube brazing techniques rather than finger stock RF joints in its construction. We report on recent improvements made to the cathode and to the extractor in order to improve the shot-to-shot reproducibility of the tube by eliminating breakdown at triple points. Results from optimizing the impedance match of the extractor circuit to the tube, which has been predicted to increase the output power by up to 50%, are also presented. Finally, we report on Hard-Tube MILO results when using the recently upgraded IMP pulser. This upgrade gives us the potential to increase the output microwave pulse duration from its previously pulsed-power-limited value of 170 ns (FWHM) to nearly 500 ns.