A table‐top PXI based low‐field spectrometer for solution dynamic nuclear polarization. (24th November 2017)

• Record Type: Journal Article
• Authors: Biller, Joshua R.; Stupic, Karl F.; Moreland, J.
• Is Part Of: Magnetic resonance in chemistry. Volume 56:Number 3(2018)
• Page Start: 153
• Page End: 163
• Publication Date: 2017-11-24
• Subjects: 1H -- DNP -- Hyperpolarization -- LabVIEW -- Nitroxide -- PXI -- Resonator efficiency; Nuclear magnetic resonance spectroscopy -- Periodicals; Chemistry, Organic -- Periodicals; Magnetic resonance -- Periodicals; 538.36
• DOI: 10.1002/mrc.4672
• Languages: English
• ISSNs: 0749-1581

Abstract

Abstract : We present the development of a portable dynamic nuclear polarization (DNP) instrument based on the PCI eXtensions for Instrumentation platform. The main purpose of the instrument is for study of 1 H polarization enhancements in solution through the Overhauser mechanism at low magnetic fields. A DNP probe set was constructed for use at 6.7 mT, using a modified Alderman–Grant resonator at 241 MHz for saturation of the electron transition. The solenoid for detection of the enhanced 1 H signal at 288 kHz was constructed with Litz wire. The largest observed 1 H enhancements (ε) at 6.7 mT for 14 N‐CTPO radical in air saturated aqueous solution was ε~65. A concentration dependence of the enhancement is observed, with maximum ε at 5.5 mM. A low resonator efficiency for saturation of the electron paramagnetic resonance transition results in a decrease in ε for the 10.3 mM sample. At high incident powers (42 W) and long pump times, capacitor heating effects can also decrease the enhancement. The core unit and program described here could be easily adopted for multi‐frequency DNP work, depending on available main magnets and selection of the "plug and play" arbitrary waveform generator, digitizer, and radiofrequency synthesizer PCI eXtensions for Instrumentatione cards. Abstract : A low‐cost homebuilt digital dynamic nuclear polarization spectrometer was constructed with commercially available boards. The operational range of the current configuration is up to 1 GHz (40 mT), with demonstration at 6.7 mT. A maximum ε~65 was observed for air saturated nitroxide solutions. Details are provided on probe construction, and experimental artifacts which can decrease enhancement. The overall goal is an easily reproducible system that can be adopted for dynamic nuclear polarization measurements in other laboratories.