Improved waveguide coupling for 1.3 mm MAS DNP probes at 263 GHz
Abstract
We consider the geometry of a radially irradiated microwave beam in MAS DNP NMR probes and its impact on DNP enhancement. Two related characteristic features are found to be relevant: (i) the focus of the microwave beam on the DNP MAS sample and (ii) the microwave magnetic field magnitude in the sample. We present a waveguide coupler setup that enables us to significantly improve beam focus and field magnitude in 1.3 mm MAS DNP probes at a microwave frequency of 263 GHz, which results in an increase of the DNP enhancement by a factor of 2 compared to previous standard hardware setups. We discuss the implications of improved coupling and its potential to enable cutting-edge applications, such as pulsed high-field DNP and the use of low-power solid-state microwave sources.
- Publication:
-
Journal of Magnetic Resonance
- Pub Date:
- May 2019
- DOI:
- 10.1016/j.jmr.2019.03.009
- Bibcode:
- 2019JMagR.302...43P
- Keywords:
-
- Dynamic nuclear polarization;
- DNP;
- Sub-THz microwave fields;
- Simulation of electromagnetic fields;
- Nuclear magnetic resonance;
- Solid-state NMR instrumentation;
- Magic angle spinning