Magnetic-lens-generated polarized neutron beam with enhanced intensity and <i>Q</i> resolution for small-angle neutron scattering

We installed a 30 mm-bore 3.2 m-long magnetic lens in the small-angle neutron scattering diffractometer (SANS-J) at the Japan Research Reactor 3 to focus the neutron beam near the sample position for measurements at <i>Q</i> > 0.1 nm^-1. The focused beam at the sample position was over three times more intense than the standard non-focused beam, while the <i>Q</i> resolution was improved. The positive spin component of the neutron beam was focused near the sample, whereas the negative spin component was defocused and blocked by the slit just in front of the sample, producing a polarized beam. The 8 mm-diameter focusing polarized beam achieved a polarization of 0.95-0.96 and an intensity up to 22 times greater than that of a non-focusing polarized beam with the same collimation length. Using this beam with a remanent supermirror-coated spin analyser, we demonstrate that polarization analysis measurements of hydrogen-containing samples can be completed within tens of minutes.