Low-Temperature Dynamic Nuclear Polarization of Gases in Frozen Mixtures

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Abstract

Purpose:

To present a new cryogenic technique for preparing gaseous compounds in solid mixtures for polarization using dynamic nuclear polarization (DNP).

Methods:

129Xe and 15N2O samples were prepared using the presented method. Samples were hyperpolarized at 1.42K at 5 Tesla. 129Xe was polarized at 1.65K and 1.42K to compare enhancement. Polarization levels for both samples and T1 relaxation times for the 129Xe sample were measured. Sample pulverization for the 129Xe and controlled annealing for both samples were introduced as additional steps in sample preparation.

Results:

Enhancement increased by 15% due to a temperature drop from 1.65K to 1.42K for the 129Xe sample. A polarization level of 20 ± 3% for the 129Xe sample was achieved, a two-fold increase from 10 ± 1% after pulverization of the sample at 1.42K. T1 of the 129Xe sample was increased by more than three-fold by means of annealing. In the case of 15N2O, annealing led to a ∼two-fold increase in the signal level after DNP.

Conclusion:

The presented technique for producing and manipulating solid gas/glassing agent/radical mixtures for DNP led to high polarization levels in 129Xe and 15N2O samples. These methods show potential for polarizing other gases using DNP technology. Magn Reson Med 76:1007–1014, 2016. © 2015 Wiley Periodicals, Inc.

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