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  

Fujisawa, H.

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.

 

slides icon

Slides

 
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.