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LINAC08 - List of Authors (Otono, H.)
A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z
Development of Modulating Permanent Magnet Sextupole Lens for Focusing of Pulsed Cold Neutrons
M. Yamada, H. Fujisawa, M. Ichikawa, Y. Iwashita, H. Tongu
K. Hirota, Y. Otake, H. Sato
T. Ino, K. Mishima, T. Morishima, S. Mutou, H.M. Shimizu, K. Taketani
Y. Kamiya, S. Kawasaki, S. Komamiya, H. Otono, S. Yamashita
University of Tokyo, Tokyo
T. Oku, K. Sakai, T. Shinohara, J. Suzuki
We are developing a modulating permanent magnet sextupole lens to focus pulsed cold neutrons. It is based on te extended Halbach configuration to generate stronger magnetic field. In order to adjust te strength, te magnet is divided into two nested co-axial rings, where te inner ring is fixed and te outer ring can be rotated. Synchronizing te modulation with neutron beam pulse suppresses te chromatic aberration. These devices largely improve te utilization efficiency of neutrons, which makes even small linac based neutron sources practical. We have fabricated a half-scale model and studied its strength, torque and temperature rise during te operation. Te main causes of te temperature rise are eddy-current loss in te poles made of soft magnetic material in inner ring and hysteresis loss. A laminated structure reduced te eddy-current loss. Te temperature rise was suppressed to about half of te former model. We now study their B-H curve to optimize te thickness of te sheet. Annealing of te material is supposed to reduce te hysteresis loss, which will be tested soon. Te experimental results of very-cold neutrons focusing with te half-scale model are also described.