1. Dynamic nuclear polarization at 700MHz/460GHz
- Author
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Sudheer Jawla, Emilio A. Nanni, Robert G. Griffin, Ajay Thakkar, Elijah L. Mena, Ronald DeRocher, Eugenio Daviso, Richard J. Temkin, Paul P. Woskov, Evgeny Markhasin, Vladimir K. Michaelis, Judith Herzfeld, Alexander B. Barnes, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Francis Bitter Magnet Laboratory (Massachusetts Institute of Technology), Barnes, Alexander, Markhasin, Evgeny, Daviso, Eugenio, Michaelis, Vladimir K., Nanni, Emilio Alessandro, Jawla, Sudheer K., Mena, Elijah L., DeRocher, Ronald C, Thakkar, Ajay V, Woskov, Paul P, Temkin, Richard J, and Griffin, Robert Guy
- Subjects
Nuclear and High Energy Physics ,Magnetic Resonance Spectroscopy ,Materials science ,business.industry ,Transducers ,Biophysics ,Refrigerator car ,Analytical chemistry ,Refrigeration ,Equipment Design ,Cryogenics ,Microwave transmission ,Liquid nitrogen ,Condensed Matter Physics ,Biochemistry ,Article ,Specimen Handling ,Equipment Failure Analysis ,Heat exchanger ,Optoelectronics ,business ,Spinning ,Microwave - 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 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., National Institutes of Health (U.S.) (EB002804), National Institutes of Health (U.S.) (EB003151), National Institutes of Health (U.S.) (EB002026), National Institutes of Health (U.S.) (EB001960), National Institutes of Health (U.S.) (EB001035), National Institutes of Health (U.S.) (EB001965), National Institutes of Health (U.S.) (EB004866)
- Published
- 2012
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