Improved NMR resonator for diamond anvil cells

A new hairpin resonator efficiently couples to nuclear spins in diamond anvil cell-nuclear magnetic resonance (DAC-NMR) experiments. The hairpin resonator is essentially a single turn coil of copper sheet, resonated with a chip capacitor. A modest tuning range is provided by trimmer capacitors. This resonator has so far been the most satisfactory of the DAC-NMR schemes tried in our laboratory. It is easy to make, robust, and reusable, and is easily cleaned to eliminate contaminant signals. The H₁ homogeneity is good; the rf performance is described.