Preliminary Experiment on enhanced DNP-NMP system based on a frequency-tunable terahertz gyrotron

A 263GHz frequency-tunable gyrotron is investigated theoretically and experimentally, its frequency-tuning range is 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 gyrotron's operating mode TE 72 mode is converted into a linearly gaussian beam efficiently with a quasi-optical mode converter. The Gaussian beam is transmitted and focused with a low loss with overmoded corrugated waveguides and quasi-optical units. The preliminary experiment on enhanced DNP-NMR system is carried out with the frequency-tunable gyrotron, the quasi-optical mode converter and the overmoded corrugated waveguides.