Generation, propagation and diagnostics of a long pulse annular electron beam for an HPM source

We are in the process of re-assembling the injection-locked relativistic Klystron oscillator to increase the duration of the high power microwave pulse. This HPM source is designed to use a 500 kV, 10 kA annular electron beam and generate /spl sim/1.5 GW microwave pulse. Previously we published that the microwave pulse length was experimentally observed to be limited to a finite change in the beam current. These initial experiments focus on controlling the total variation of the emitted beam current. That is, our goal is to have the vacuum diode behave as a resistive load at the desired voltage. We will be presenting results of experiments on the materials used to fabricate the cathode and its emission surface, results from X-ray and optical diagnostics of the unmodulated electron beam position and thickness, and finally results from X-ray and optical diagnostics of the modulated electron beam position and thickness. These results will be compared with different time dependent and steady state computational tools.