Recent progress at MIT on THz gyrotron oscillators for DNP/NMR

Signal-to-noise is a key ingredient in successful NMR experiments, a fact that has stimulated the development of dynamic nuclear polarization (DNP). In solid state magic angle spinning (MAS) NMR experiments, we have observed signal enhancements of 50-400 at 140 and 250 GHz operating frequencies, depending on a variety of experimental conditions. These experiments are possible because of the development of gyrotrons for generating the high frequency microwaves needed for DNP/NMR. We report progress in the development of tunable gyrotrons at 330 and 460 GHz for DNP/NMR spectroscopy. The successful recent demonstration of DNP/NMR enhancements using the 460 GHz gyrotron with a 700 MHz NMR spectrometer makes it the highest frequency DNP/NMR system currently in operation worldwide. A 527 GHz gyrotron is now under development for application in an 800 MHz NMR system. We present an overview of the systems and related THz technologies developed at MIT for DNP/NMR spectroscopy.