Title:

Techniques for Dynamic Nuclear Polarization NMR Analysis of Spin 1 Systems

Polarized target material is essential for the study of nucleon spin structure in high energy scattering experiments. The polarization of manufactured targets must be known prior to their use in an accelerator. Nuclear magnetic resonance (NMR) is used to determine the polarization of the target material. The polarization is computed by comparing the NMR signal size (area) to that of a reference where the polarization is known. Currently, the known polarization value is calculated at thermal equilibrium (TE) where Boltzmann statistics describe the equilibrium polarization. Unfortunately, the signal TE is tiny and must be obtained from thousands of sweeps over many days to separate the signal from the noise. Maintaining the low temperature (1 K) and magnetic field (5 T) required for the TE over extended periods of time is a difficult experimental demand. Ideally, our polarization reference would generate a large NMR signal. While it is easy to obtain a large signal during manufacturing, Boltzmann statistics no longer apply for calculating polarization. Past efforts have exploited the signal shape to determine polarization (O.Hamada et al., C.Dulya et al., W.F.Kielhorn). Such methods employ the use of complex mathematical fits and functions to describe the data. These methods can fail to model the polarization of the target accurately during the dynamic nuclear polarization process (when the microwave system is on). Two alternative hybrid methods for fitting the data and determining polarization from signal shape will be proposed and the potential drawbacks of both discussed. The first relies on the ratio of peaks and plateaus in a spin 1 NMR signal, and the second exploits the signal symmetry from spin transitions. Both methods use large NMR signals and allow for accurate polarization measurements without a TE signal, providing correct results throughout the dynamic nuclear polarization process.

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