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Yamada, M.

Paper Title Page
MOP079 Development of Modulating Permanent Magnet Sextupole Lens for Focusing of Pulsed Cold Neutrons 263
  • 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, Tsukuba
  • 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.


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TUP054 Development of the Continuously Adjustable Permanent Magnet Quadrupole for ATF2 524
  • T. Sugimoto, M. Ichikawa, Y. Iwashita, I. Kazama, M. Yamada
    Kyoto ICR, Uji, Kyoto
  • T. Tauchi
    KEK, Ibaraki

A final focus quadrupole (FFQ) doublet of ILC should have excellent properties such as strong focusing, compactness and less vibrations. In a baseline design, superconducting magnet is supposed to be used, which may have some vibrations traveling through liquid helium. It may not be suitable for FFQ of ILC unless the vibration effect is proven to be negligible. Since the five-disc-singlet proposed by Gluckstern satisfies these properties including continuous adjustability, we are developing a FFQ aiming at a beam test at ATF2. Although the x-y coupling effect is carefully cancelled in the design, fabrication errors or rotation errors may break the cancellation. We are estimating the effect of these errors on the beam size at the interaction point. Two methods are currently carried out. The first one is transfer matrix calculations, which neglects fringing field and higher multipole components. The second one is beam-tracking calculation in measured or calculated magnetic field. The fabricated magnet is under adjustment measuring the magnetic field. The recent results will be presented.

TUP116 Development of Very Small ECR Ion Source with Pulse Gas Valve 673
  • M. Ichikawa, H. Fujisawa, Y. Iwashita, T. Sugimoto, H. Tongu, M. Yamada
    Kyoto ICR, Uji, Kyoto

We aim to develop a small and high intensity proton source for a compact accelerator based neutron source. Because this proton source shall be located close to RFQ for simplification, ratio of H+ to molecular ions such as H2+ or H3+ must be large. Therefore we select ECR ion source with permanent magnet as a small and high intensity ion source. ECR ion sources can provide high H+ ratio because of their high plasma temperature. Using permanent magnets makes the ion source small and running cost low. Because there is no hot cathode, longer MTBF is expected. Usually, gas is fed into ion sources continuously, even if ion sources run in pulse operation mode. But, continuous gas flow doesn't make vacuum in good level. So, we decided to install pulse gas valve directly to the plasma chamber. Feeding the gas only when the ion source is in operation reduces the gas load to the evacuation system and the vacuum level can be kept high. Recent experimental results will be presented.