Dynamic nuclear polarization at 700MHz/460GHz
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Griffin_Dynamic nuclear.pdf
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663.18 KB
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Checksum (MD5)
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Author(s)
Herzfeld, Judith
Barnes, Alexander
Markhasin, Evgeny
Daviso, Eugenio
Michaelis, Vladimir K.
Nanni, Emilio Alessandro
Jawla, Sudheer K.
Mena, Elijah L.
Thakkar, Ajay V
Temkin, Richard J
Date Issued
August 2012
Journal
Journal of Magnetic Resonance
Publisher
Elsevier
Citation
Barnes, Alexander B.; Markhasin, Evgeny; Daviso, Eugenio; Michaelis, Vladimir K.; Nanni, Emilio A.; Jawla, Sudheer K. and Mena, Elijah L. et al. “Dynamic Nuclear Polarization at 700MHz/460GHz.” Journal of Magnetic Resonance 224 (November 2012): 1–7 © 2012 Elsevier Inc
Version
Author's final manuscript
Abstract
We describe the design and implementation of the instrumentation required to perform DNP-NMR at higher field strengths than previously demonstrated, and report the first magic-angle spinning (MAS) DNP-NMR experiments performed at ¹H/e⁻ frequencies of 700 MHz/460 GHz. The extension of DNP-NMR to 16.4 T has required the development of probe technology, cryogenics, gyrotrons, and microwave transmission lines. The probe contains a 460 GHz microwave channel, with corrugated waveguide, tapers, and miter-bends that couple microwave power to the sample. Experimental efficiency is increased by a cryogenic exchange system for 3.2 mm rotors within the 89 mm bore. Sample temperatures ⩽85 K, resulting in improved DNP enhancements, are achieved by a novel heat exchanger design, stainless steel and brass vacuum jacketed transfer lines, and a bronze probe dewar. In addition, the heat exchanger is preceded with a nitrogen drying and generation system in series with a pre-cooling refrigerator. This reduces liquid nitrogen usage from >700 l per day to <200 l per day and allows for continuous (>7 days) cryogenic spinning without detrimental frost or ice formation. Initial enhancements, ε = −40, and a strong microwave power dependence suggests the possibility for considerable improvement. Finally, two-dimensional spectra of a model system demonstrate that the higher field provides excellent resolution, even in a glassy, cryoprotecting matrix.
MIT Department
Massachusetts Institute of Technology. Plasma Science and Fusion Center
Francis Bitter Magnet Laboratory (Massachusetts Institute of Technology)
Terms of Use
Creative Commons Attribution-NonCommercial-NoDerivs License
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DOI of Published Version
https://doi.org/10.1016/j.jmr.2012.08.002
