• M. Yamada, H. Fujisawa, M. Ichikawa, Y. Iwashita, H. Tongu
  Kyoto ICR, Uji, Kyoto
• P. Geltenbort
  ILL, Grenoble
• K. Hirota, Y. Otake, H. Sato
  RIKEN, Wako, Saitama
• T. Ino, K. Mishima, T. Morishima, S. Mutou, H.M. Shimizu, K. Taketani
  KEK, Ibaraki
• Y. Kamiya, S. Kawasaki, S. Komamiya, H. Otono, S. Yamashita
  University of Tokyo, Tokyo
• T. Oku, K. Sakai, T. Shinohara, J. Suzuki
  JAEA, Ibaraki-ken
• Y. Seki
  Kyoto University, Kyoto
• T. Yoshioka
  ICEPP, Tokyo

We are developing a modulating permanent magnet sextupole lens to focus pulsed cold neutrons. It is based on the extended Halbach configuration to generate stronger magnetic field. In order to adjust the strength, the magnet is divided into two nested co-axial rings, where the inner ring is fixed and the outer ring can be rotated. Synchronizing the modulation with neutron beam pulse suppresses the chromatic aberration. These devices largely improve the 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 the operation. The main causes of the temperature rise are eddy-current loss in the poles made of soft magnetic material in inner ring and hysteresis loss. A laminated structure reduced the eddy-current loss. The temperature rise was suppressed to about half of the former model. We now study their B-H curve to optimize the thickness of the sheet. Annealing of the material is supposed to reduce the hysteresis loss, which will be tested soon. The experimental results of very-cold neutrons focusing with the half-scale model are also described.

Slides

• V. Sajaev
  ANL, Argonne

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An energy recovery linac (ERL) is one of the candidates for an upgrade of the Advanced Photon Source (APS). In addition to the APS ring and full-energy linac, our design also includes a large turn-around arc that could accommodate new X-ray beamlines as well. In total, the beam trajectory length would be close to 3 km. The ERL lattice has a strong focusing to limit emittance growth, and it includes strong sextupoles to keep beam energy spread under control and minimize beam losses. As in storage rings, trajectory errors in sextupoles will result in lattice perturbations that would affect delivered X-ray beam properties. In storage rings, the response matrix fit method is widely used to measure and correct linear lattice errors. Here, we explore the application of the method to the linear lattice correction of ERL.