The performance of magnetic lens for focusing VCN-SANS

We have developed a prototype rotating-permanent magnet sextupole lens (named rot-PMSx) for more efficient experiments with neutron beams in time of flight (ToF) mode. This lens can modulate the focusing strength over range 1.5 x 10(4)T/m(2) <= g' <= 5.9 x 10(4) T/m(2). Synchronization between the modulation and the beam pulse produces a focused beam without significant chromatic aberration. We anticipate that this lens could be utilized in focusing small angle neutron scattering (SANS) instruments for novel approach to high resolution SANS. We carried out experiments testing the principle of this lens at the very cold neutron (VCN) beamline (PF2) at Institut Laue-Langevin (ILL), France. The focused beam image size at the detector was kept constant at the same beam size as the source (approximate to 3 mm) over a wavelength range of 30 angstrom <= lambda <= 48 angstrom in focal length of approximate to 1.14m. The flux gain was about 12 relative to a beam without focusing, and the depth of focus was quite large. These results show the good performance of this lens and the system. Thereupon we have demonstrated the performance of this test bed for high resolution focusing of VCN-SANS for a well-studied softmatter sample; a deuterium oxide solution of Pluronic F127, an (PEO)(100)(PPO)(65)(PEO)(100) tri-block copolymer in deuterium oxide. The results of the focusing experiment and the focusing VCN-SANS are presented. (C) 2010 Elsevier B.V. All rights reserved.

Keywords

Small angle scattering, Pulsed neutron techniques, Deuterium, Magnetic lens spectrometers, Magnetic flux, Synchronization

Citation

Yamada, M., Iwashita, Y., Kanaya, T., Ichikawa, M., Tongu, H., Kennedy, S.J., Shimizu, H.M., Mishima, K., Yamada, N.L., Hirota, K., Carpenter, J.M., Lal, J., Andersen, K., Geltenbort, P., Guerard, B., Manzin, G., Hino, M., Kitaguchi, M., & Bleuel, M. (2011). The performance of magnetic lens for focusing VCN-SANS. Paper presented to the International Workshop on Neutron Optics NOP2010, 17-19 March, Alpe d'Huez, France. In Andersen, K. H., Bentley, P., Bigault, T., Courtois, P., Cubitt, R. (Eds), Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 634(1), S156-S160. doi:10.1016/j.nima.2010.06.259