Recent progress in the dynamic nuclear polarization of solid deuterated butanol targets

Polarized solid targets have been used in nuclear and particle physics experiments since the early 1960s, and with the development of superconducting magnets and He-3/He-4 dilution refrigerators in the early 1970s, proton polarization values of 80-100% have been achieved routinely in various target materials at two standard magnetic field and temperature conditions (2.5 T, <0.3 K and 5 T, 1 K). Due to the much lower magnetic moment of the deuteron compared with that of the proton, deuteron polarization values have been considerably lower, typically 30-40% in chemically doped alcohols (d-butanol), 40-45% in radiation-doped ammonia (ND3), and 50-55% in irradiated lithium-deuteride. Now, however, research at the University of Bochum - including systematical electron spin resonance (ESR) investigations in order to study the properties of the paramagnetic dopants (i.e., their ESR line width) - is yielding alcohol and diol materials with deuteron polarizations as high as 80%.