Author: Hasegawa, K.
Paper Title Page
TUODB201 Recent Progress on the Development of a High Gradient RF System using High Impedance Magnetic Alloy, FT3L 1152
 
  • C. Ohmori, K. Hara, K. Hasegawa, M. Toda, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
  • M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura, Japan
 
  An upgrade project of J-PARC MR (Main Ring) includes developments of high gradient RF cavities and magnet power supplies for high repetition rate. A dedicated production system for high impedance magnetic alloy (FT3L) cores was assembled in J-PARC. This setup demonstrated that we can produce material with two times higher muQf product compared to the cores used for present cavities. And, the new results also show up to 20% higher impedance than the 2011 production with the former setup. In this summer, the system will be used for mass production of 200 FT3L cores for J-PARC MR. The cores produced in 2011 are already used for standard machine operation. The operation experience shows that the power loss in the cores was reduced significantly as expected. The scenario describing the upgrade plan of MR and the cavity replacements is reported. By the replacement plan, the total acceleration voltage will be almost doubled, while the number of RF stations remains the same.  
slides icon Slides TUODB201 [5.105 MB]  
 
TUPME019 Simulation for Control of Longitudinal Beam Emittance in J-PARC MR 1610
 
  • M. Yamamoto, M. Nomura, A. Schnase, T. Shimada, F. Tamura
    JAEA/J-PARC, Tokai-mura, Japan
  • E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, K. Takata, M. Toda, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
 
  The J-PARC MR receives a high intensity beam from the RCS. The designed longitudinal emittance of the RCS is 5 eVs, whereas the MR rf bucket has enough margin to accept up to 10 eVs. Although the RCS emittance can be increased by using PM method and a large emittance is desirable to increase the bunching factor and to avoid instability, it is difficult to receive such large emittance beam in the MR because of the MR kicker performance. We have performed the particle tracking simulation of longitudinal emittance control for enlarging the beam emittance by PM method and for keeping the bunching factor high using 2nd harmonic rf during the MR injection period.  
 
WEPEA019 Status of the J-PARC MA Loaded RF Systems 2537
 
  • M. Yoshii, E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, K. Takata, M. Toda
    KEK, Tokai, Ibaraki, Japan
  • M. Nomura, T. Shimada, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura, Japan
  • A. Schnase
    GSI, Darmstadt, Germany
 
  Japan proton accelerator complex operates two cascaded synchrotrons, 3GeV RCS and 50GeV MR. The high electric field gradient magnetic alloy (MA) loaded cavities are used in both synchrotrons. The RF systems have no tuning control loop and the direct digital synthesis based fully digital low level RF guarantees the stable and reproducible proton acceleration. The feed-forward systems using the circulating beam current signals works efficiently to compensate the heavy beam induced voltage. In RCS, 11 RF systems are operating in a dual harmonic mode since December 2008. The longitudinal RF control based on the particle tracking performed effectively and the equivalent beam power of 530 kW was successfully demonstrated. The 260kW operation for the neutron users started in October 2012. In MR synchrotron, the 9th RF system was newly installed and became available as a 2nd harmonic RF system in November 2012. A 30 GeV proton of 200 kW beam power has been delivered to the T2K neutrino beam experiment with 2.48 sec repetition cycle. This paper summarizes the operation details and the status and features of the J-PARC RF systems.  
 
WEPEA020 Commissioning of Beam Loading Compensation System in the J-PARC MR 2540
 
  • F. Tamura, M. Nomura, A. Schnase, T. Shimada, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • K. Hara, K. Hasegawa, C. Ohmori, M. Toda, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
 
  Beam loading compensation is indispensable to accelerate high intensity proton beams in the J-PARC MR. The MA-loaded rf cavities in the MR are driven by the single harmonic (h=9) rf signals, while the cavity frequency response covers also the neighbor harmonics (h=8, 10). The wake voltage induced by the beam consists of the three harmonics (h=8, 9, 10). We employ the rf feedforward method to compensate the beam loading of these harmonics. The full-digital feedforward system was developed for the MR. We have successfully commissioned the feedforward patterns for all of eight cavities by using high intensity beams with 1.0·1014 ppp. We present the commissioning results. The impedance seen by the beam is reduced and the longitudinal oscillations due to the beam loading are reduced. By the beam loading compensation, high power beam operation at the beam power of 200 kW has been achieved.  
 
WEPFI021 Influence of Core Winding Tension and Ribbon Quality on the MA Core RF Characteristics 2747
 
  • M. Nomura, A. Schnase, T. Shimada, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura, Japan
  • K. Hara, K. Hasegawa, C. Ohmori, M. Toda, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
 
  J-PARC 3 GeV Rapid Cycling Synchrotron (RCS) and Main Ring (MR) employ RF cavities loaded with Magnetic Alloy (MA) cores to generate a high field gradient. To achieve the high field gradient, the core shunt impedance is a key parameter. We found during the development of MA cores for RCS RF cavities that the core shunt impedance was increased by lowering a core winding tension. We lowered the core winding tension in order to improve the electrical insulation between MA ribbon layers. The lower winding tension reduced the core filling factor that is defined as the volume ratio of MA ribbons and geometrical dimensions. The core shunt impedance might be reduced according to the core filling factor reduction. We discuss the reason why the lower winding tension increased the core shunt impedance. We also report the influence of the ribbon quality variation on the MA core RF characteristics.  
 
WEPFI022 Inner Diameter Change over the Years of MA Cores of RF-cavities at the J-PARC 3 GeV Synchrotron 2750
 
  • T. Shimada, M. Nomura, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura, Japan
  • K. Hara, K. Hasegawa, C. Ohmori, M. Toda, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
  • A. Schnase
    GSI, Darmstadt, Germany
  • H. Suzuki
    Japan Atomic Energy Agency (JAEA), International Fusion Energy Research Center (IFERC), Rokkasho, Kamikita, Aomori, Japan
 
  The 11 RF cavities at the J-PARC 3 GeV synchrotron use 198 MA cores. Buckling occurred in some cores since the operation started in October 2007. We have measured the inner diameters of the cores as part of the investigation to determine the cause of buckling when the cavities were disassembled for maintenance. We obtained inner diameter change values of 36 cores over a longer than 2 years interval in the summer of 2012. We noticed deformations of the inner shapes of the cores related to the manufacturing process, and that inner diameter changes over this period were not detected in most of the cores without buckling. Furthermore, an effective core manufacturing process to avoid the buckling has been established. We are going to replace old type cores with new type cores in summer shutdown periods every year and will have finished the replacement work by the summer of 2013. We report the relation between inner shapes of the cores and the manufacturing process and inner shape changes over the years.