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Published on: March 30, 2017
Dynamic nuclear polarization by frequency modulation of a tunable gyrotron of 260GHz
Dongyoung Yoon1, Murari Soundararajan1, Philippe Cuanillon1
1École Polytechnique Fédérale de Lausanne, Institute of Condensed Matter Physics, CH-1015 Lausanne-EPFL, Switzerland.
Abstract:
An increase in Dynamic Nuclear Polarization (DNP) signal intensity is obtained with a tunable gyrotron producing frequency modulation around 260GHz at power levels less than 1W. The sweep rate of frequency modulation can reach 14kHz, and its amplitude is fixed at 50MHz. In water/glycerol glassy ice doped with 40mM TEMPOL, the relative increase in the DNP enhancement was obtained as a function of frequency-sweep rate for several temperatures. A 68 % increase was obtained at 15K, thus giving a DNP enhancement of about 80. By employing λ/4 and λ/8 polarizer mirrors, we transformed the polarization of the microwave beam from linear to circular, and achieved an increase in the enhancement by a factor of about 66% for a given power.
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