Production of a polarizable target using mechanical doping method and trial of dynamic nuclear polarization

Dynamic Nuclear Polarization (DNP) which is often employed for polarized solid targets, needs free electron doping to transfer high electron polarization to target nuclei. A newly proposed “mechanical-doping” method was applied in preparation of a polarized target material. A solid material having been crushed into small particles with a diameter of about 20 nm, is mixed with a free radical. This allows target nuclei to have more chance to interact with the free electrons or polarized nuclei surrounding the small particles. A first DNP test at a magnetic field of 2.5 T and a temperature of 0.9 K was performed with a sample of LaF_{3} processed in the mechanical-doping method to introduce a free radical TEMPO dispersed in ethanol. ^{19}F polarizations of 3.3 % and -2.7 % were achieved. The obtained polarization enhancement for ^{19}F demonstrated effectiveness of the new method.