CW second harmonic results at 460 GHz of a gyrotron oscillator - for sensitivity enhanced NMR

We report 460 and 233 GHz CW results of a gyrotron operating at the second electron cyclotron harmonic and fundamental, respectively. A record CW power level of over 8 W has been obtained at 460 GHz in the TE_0,6 mode with 12.4 kV and 135 mA. The gyrotron has operated under computer control for over an hour with stable power output of better than 1%. Fundamental CW studies at 233 GHz in the TE_2,3 mode reveal that oscillations start with less than 7 W of beam power below 3.5 kV. The gyrotron will extend sensitivity-enhanced NMR through dynamic nuclear polarization to the highest field ever used, 16.5 T (700 MHz ¹H).