Dynamic nuclear polarization requires a waveguide that connects the cold (1–10 K) sample space to the outside. To reduce the heating of the sample, a waveguide is produced from steel which has low thermal conductivity but attenuates the microwaves. Therefore, the inside of the waveguide should be plated with silver to reduce electrical losses. We show a new simple way to electroplate such waveguides with a thin silver layer and show that this improves the experimental performance.

The signals that are attainable in conventional NMR are tiny, and consequentially, NMR is often slow and insensitive. The intensity may be increased by hyperpolarization, provided that the spectral quality is essentially preserved. We have recently reported a potentially powerful hyperpolarization scheme, named bullet-DNP (dynamic nuclear polarization). Here, we report a 10-fold improvement in resolution for that method, which may enable new applications in metabolomics and drug discovery.

The sensitivity of magnetic resonance imaging can be increased by coupling of the less sensitive nuclear spins which are excited at radio frequencies to unpaired electron spins of radicals which are excited at microwave frequencies. Here we demonstrate how a Fabry–Perot-type microwave resonance structure can be used to significantly enhance the polarization transfer from electron to water proton nuclear spins under constant flow conditions for imaging applications at 1.5 T.