  We report on a polarized-neutron Laue diffraction experiment on a single
crystal of neodynium doped lanthanum magnesium nitrate hydrate containing
polarized proton spins. By using dynamic nuclear polarization to polarize the
proton spins, we demonstrate that the intensities of the Bragg peaks can be
enhanced or diminished significantly, whilst the incoherent background, due to
proton spin disorder, is reduced. It follows that the method offers unique
possibilities to tune continuously the contrast of the Bragg reflections and
thereby represents a new tool for increasing substantially the signal-to-noise
ratio in neutron diffraction patterns of hydrogenous matter.
