Enhancement of nuclear polarization with frequency modulated microwaves
The authors report their discovery of a gain by a factor of two in the growth rate and of a gain by {approx} 1.7 in the maximum dynamic nuclear polarization (DNP) of deuteron in the large polarized targets of the Spin Muon Collaboration. These large gains resulted from a frequency modulation (FM) of the {approx} 69 GHz microwave field used for DNP; this FM had a 30 MHz amplitude and {approx} 1 KHz frequency. The target material is glassy deuterated 1-butanol doped with a paramagnetic Cr(V) complex. Measurements of the 430 MHz broad electron paramagnetic resonance (EPR) absorption spectrum in the 2.5 T field were performed by a novel differential bolometric technique. They show that FM gives rise to an additional microwave absorption which depends on the amplitude and frequency of FM and which is more pronounced in the edges of the EPR spectrum. For deuterons, polarizations of 0.46 and {minus}0.53 have been obtained. Similar although less dramatic effects were observed for protons where FM increased the polarization by less than 10% and the growth rate by {approx} 20%.
- OSTI ID:
- 374940
- Report Number(s):
- CONF-9304297-; ISSN 0003-0503; TRN: 96:004080-0327
- Journal Information:
- Bulletin of the American Physical Society, Vol. 40, Issue 2; Conference: 1993 joint meeting of the American Physical Society and the American Association of Physics Teachers, Washington, DC (United States), 12-15 Apr 1993; Other Information: PBD: Apr 1995
- Country of Publication:
- United States
- Language:
- English
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