Dynamic Nuclear Polarization System Research Articles

Portable X-band system for solution state dynamic nuclear polarization

This paper concerns instrumental approaches to obtain large dynamic nuclear polarization (DNP) enhancements in a completely portable system. We show that at fields of 0.35T under ambient conditions and at X-band frequencies, 1H enhancements of >100-fold can be achieved using nitroxide radical systems, which is near the theoretical maximum for 1H polarization using the Overhauser effect at this field. These large enhancements were obtained using a custom built microwave transmitter and a commercial TE102 X-band resonant cavity. The custom built microwave transmitter is compact, so when combined with a permanent magnet it is readily transportable. Our commercial X-band resonator was modified to be tunable over a range of ∼9.5–10GHz, giving added versatility to our fixed field portable DNP system. In addition, a field adjustable Halbach permanent magnet has also been employed as another means for matching the electron spin resonance condition. Both portable setups provide large signal enhancements and with improvements in design and engineering, greater than 100-fold 1H enhancements are feasible.

Development of a dynamic nuclear polarization system based on the optical pumping method

We have developed a dynamic nuclear polarization system based on the optical pumping NMR method. It consists of an NMR spectrometer, laser and optical system, optical-pumping double-resonance probe, cryostat and superconducting magnet. The double-resonance probe newly developed for this system is of a top-loading type, characterized by a single-coil double-tuning tank circuit with traps. The system allows simultaneous control of two radio-frequency fields and a light beam irradiated to samples, enabling us to perform cross-polarization experiments under the optical pumping condition. As a test of the system, a cross-polarization experiment has been performed with indium phosphide doped with iron.