A 140 GHz gyro-amplifier using a dielectric-loaded, sever-less confocal waveguide

摘要

We report results of the high gain operation of a pulsed 140 GHz gyro-amplifier system under development at MIT for pulsed Dynamic Nuclear Polarization NMR (DNP-NMR). With a 46 kV, 3 A beam, the gyro-amplifier operated with 23 dB of device gain at 140 GHz, measured from the input port to the output port. With input / output coupling losses estimated at 12 dB, the gain of the confocal circuit itself is estimated to be 35 dB at 140 GHz. The gyro-amplifier uses a sever-less, confocal geometry to provide an overmoded interaction circuit with reduced mode competition. Higher gain has been achieved by including ceramic absorbers in order to attenuate unwanted oscillations due to spatial modes that are reflected from the outer vacuum tube wall.