A 460 GHz gyrotron oscillator for use in DNP/NMR spectroscopy

Summary form only given, as follows. We report the design of a gyrotron oscillator for continuous operation at 460 GHz at a power level of 25 to 100 W. The gyrotron oscillator are used for electron paramagnetic resonance (EPR) studies at 460 GHz and for dynamic nuclear polarization (DNP) studies with a 700 MHz, 16.5 T NMR system. The gyrotron design is closely modeled on a previous successful design of a 25 W, 250 GHz CW gyrotron oscillator. The present design operates at the second harmonic of the cyclotron frequency, /spl omega/-2/spl omega//sub c/. Second harmonic operation requires careful analysis in order to optimize the oscillator design under conditions of high ohmic loss. In addition, an internal mode converter is used. The output radiation travels out of the tube through a window and perpendicular to the magnetic field through a cross-bore pipe in the magnet. Details of the experimental design are presented.