Second Harmonic 527 GHz Gyrotron for DNP-NMR

We have built a frequency tunable 527 GHz gyrotron for an 800 MHz DNP-NMR spectrometer. The gyrotron is designed at the second harmonic (ω=2ω
_c
) of the electron cyclotron frequency. It produces ~10 W continuous microwave power at 527.12 GHz frequency using a diode type electron gun (V ~ 16.5 kV, I
_b
~110 mA). The gyrotron is tunable within ~ 0.5 GHz by combining voltage and magnetic field tuning. The gyrotron comprises an internal periscope assembly to internally convert a Gaussian beam to an HE
₁₁
mode in a 12 mm i.d. corrugated waveguide. The corrugated waveguide transmission line system is built including 3 m long 16 mm i.d. waveguide and a corrugated taper from 12 mm to 16 mm i.d. waveguide.