Dynamic nuclear polarization apparatus for contrast variation neutron scattering experiments on iMATERIA spectrometer at J-PARC

We have introduced a 7 T dynamic nuclear polarization apparatus for contrast variation neutron scattering experiments on iMATERIA spectrometer at the Materials and Life Science Facility at the J-PARC spallation neutron source. At 1.2 K and 6.7 T, we have achieved high proton spin polarizations (76%/$-$84%) and short buildup time constants (3.2 min/4.1 min) for a polystyrene cast film doped with 50 mM 2,2,6,6-tetramethylpiperidine 4-oxy (TEMPO), after applying microwave frequency modulation. The instrument realizes easy sample exchange and significant contrast variation beyond what is available by deuterium substitution.