Pulsed RF Signal Diagnostic System for Cyro-Amplified Research

摘要

The diagnostic equipment purchased under this DURIP grant directly supported University of Maryland basic research under the DoD MURI on Innovative Vacuum Electronics (AFOSR subcontract 99RA073403). Specifically, we studied advanced gyro-amplifiers and phase-locked oscillators operating at harmonics of the electron cyclotron frequency. Recently, a Ka-band harmonic inverted gyrotwystron (phigtron) was studied for which 720 kW of peak power, with a bandwidth of 0.7%, saturated gain of 30 dB and efficiency of 35% was demonstrated. Phase stability, noise spectrum and nonlinear gain characteristic were investigated using the new pulsed RF signal diagnostics system purchased under this grant. The experiments not only confirmed theory, but were also in very good agreement with numerical analysis using the electro-dynamic code, MAGY. The results represent the first demonstration that 'backed-off' operation improves phase stability in frequency-doubling harmonic gyro-amplifiers. The key factor for success in achieving the results has been the high dynamic range and accuracy afforded by the new diagnostic system. So far, six Ph.D. and numerous undergraduate students have employed the system in the course of their research projects. The impact on their training has been invaluable.