260 GHz quasioptical setup for EPR and DNP experiments on the 9.2 Tesla DNP/NMR/EPR spectrometer

Abstract

Transmission of microwave signals under low-losses conditions is highly demanding task in sub-mm EPR and DNP spectroscopy. We have designed and built a quasioptical setup in the Michelson interferometer configuration using oversized metallo-dielectric waveguides (MDW) of a square-shape cross-section and components such as attenuators, beam splitters, wavemeter, tapers to fundamental TE10 mode which have extremely low losses in sub-mm wave range. Following features of the setup such as total transmission losses below 2 dB from the source port to a resonator with a sample inside the cryomagnet; fine balance tuning between signal and reference channels affording up to 36 dB background signal suppression, linear-to-circular polarization conversion with a possibility to tune its phase, which allows effective suppression of reflected signal with respect to induction signal; switching between two microwave sources; and high power handling up to 20 Watt helped to reach high performance of the 9.2 Tesla DNP/NMR/EPR spectrometer. First liquid-state DNP results on nitroxide radicals in water will be presented.