A focusing-geometry small-angle neutron scattering instrument with a magnetic neutron lens

We have constructed a focusing-geometry small-angle neutron scattering (FSANS) instrument, SANS-J-II, with two kinds of neutron focusing device: a series of compound refractive lenses made of MgF2 and a magnetic neutron lens based on an extended Halbach-type sextupole magnet. In this study, we investigated the performance of the FSANS instrument with the magnetic neutron lens. The intensity distribution of a direct neutron beam focused on the detector plane by the magnetic neutron lens had a ratio of the peak height to the background level of similar to 6 x 10(4) for a polarized neutron beam with a polarization degree of similar to 0: 99. It is found that a minimum value of the measurable q range [where q is the modulus of the scattering vector and is defined as q = (4 pi / lambda) sin(theta /2), where theta is the scattering angle and lambda is the neutron wavelength], q(min), of 6.5 x 10(-4) angstrom(-1) can be achieved by the FSANS instrument with the magnetic neutron lens using neutrons with lambda = 6.6 angstrom and Delta lambda/lambda = 0.13 for the full width at half maximum.