Dynamic nuclear polarization in thin polyethylene foils cooled via a superfluid 4He film

We report on preliminary results of dynamic polarization at 2.5 T and below 0.3 K of protons in a polyethylene foil covered by a superfluid 4He film, providing the thermal contact to the mixing chamber of a dilution refrigerator. The results obtained let appear possible the development of ultrathin polarized solid targets, without solid walls and bulk liquid helium around, for particle scattering experiments.