High-power terahertz source and transmission line for 400MHz DNP NMR system

A 263GHz frequency-tunable gyrotron is investigated experimentally, its frequency-tuning range is about 1.45GHz and the output power is from 26 W to 463 W when the operating magnetic field changes at a fixed operating voltage of 20 kV and a beam current of 0.8 A. The operating mode TE
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mode is converted into a linearly gaussian beam efficiently with a Valsov-type quasi-optical mode converter. At the same time, the Gaussian beam is transmitted and focused with a low loss overmoded corrugated waveguides and quasi-optical units. The preliminary experiment on enhanced DNP-NMR system is carried out with the gyrotron and the transmission line.