MILO research at ARFL: Past and present

Summary form only given, as follows. MILO (Magnetically Insulated transmission Line Oscillator) is a crossed-field microwave tube that requires no externally applied magnetic field to insulate the electron flow under the slow-wave structure. This self-insulating property, inherent in magnetically insulated transmission lines, allows the tube to handle an extremely large input beam power (tens of gigawatts) without ensuing electrical breakdown of the anode-cathode gap. We review MILO research at AFRL, which was initiated in 1985 by Dr. Collins Clark. Experimental results have progressed from the early, radially-extracted MILOs generating 50-MW, 50-ns RF pulses to today´s gigawatt-class, axially-extracted tubes with a pulse duration of several hundred nanoseconds. Theoretical understanding of MILO physics via computer simulation has undergone a similar advancement and is also reviewed.