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Higo, T.

Paper Title Page
MOZAKI01 Compensation of the Crossing Angle with Crab Cavities at KEKB 27
 
  • K. Oide, T. Abe, K. Akai, M. Akemoto, A. Akiyama, A. Arinaga, K. Ebihara, K. Egawa, A. Enomoto, J. W. Flanagan, S. Fukuda, H. Fukuma, Y. Funakoshi, K. Furukawa, T. Furuya, K. Hara, T. Higo, S. Hiramatsu, H. Hisamatsu, H. Honma, K. Hosoyama, T. Ieiri, N. Iida, H. Ikeda, M. Ikeda, S. Isagawa, H. Ishii, A. Kabe, E. Kadokura, T. Kageyama, K. Kakihara, E. Kako, S. Kamada, T. Kamitani, K.-I. Kanazawa, H. Katagiri, S. Kato, T. Kawamoto, S. Kazakov, M. Kikuchi, E. Kikutani, K. Kitagawa, H. Koiso, Y. Kojima, K. Komada, T. Kubo, K. Kudo, N. K. Kudo, K. Marutsuka, M. Masuzawa, S. Matsumoto, T. Matsumoto, S. Michizono, K. Mikawa, T. Mimashi, S. Mitsunobu, K. Mori, A. Morita, Y. Morita, H. Nakai, H. Nakajima, T. T. Nakamura, H. Nakanishi, K. Nakao, S. Ninomiya, Y. Ogawa, K. Ohmi, Y. Ohnishi, S. Ohsawa, Y. Ohsawa, N. Ohuchi, M. Ono, T. Ozaki, K. Saito, H. Sakai, Y. Sakamoto, M. Sato, M. Satoh, K. Shibata, T. Shidara, M. Shirai, A. Shirakawa, T. Sueno, M. Suetake, Y. Suetsugu, R. Sugahara, T. Sugimura, T. Suwada, O. Tajima, S. Takano, S. Takasaki, T. Takenaka, Y. Takeuchi, M. Tawada, M. Tejima, M. Tobiyama, N. Tokuda, S. Uehara, S. Uno, Y. Yamamoto, Y. Yano, K. Yokoyama, Ma. Yoshida, M. Yoshida, S. I. Yoshimoto, K. Yoshino
    KEK, Ibaraki
  • E. Perevedentsev, D. N. Shatilov
    BINP SB RAS, Novosibirsk
  
  The crab cavities are presently being installed in the KEKB rings to compensate the crossing angle at collision and thus increase luminosity. This will be the first experience with such cavities in colliders. Results on the beam operation of the new cavities, both for single and colliding beams, will be presented including the luminosity performance and limitations.

Work presented on behalf of the KEKB Accelerator Group.

 
slides icon Slides  
WEPMN021 High Pressure Rinsing System Comparison 2092
 
  • D. Sertore, M. Fusetti, P. Michelato, C. Pagani
    INFN/LASA, Segrate (MI)
  • G. Ciovati, T. M. Rothgeb
    Jefferson Lab, Newport News, Virginia
  • T. Higo, J. H. Hong, K. Saito
    KEK, Ibaraki
  
  High pressure rinsing (HPR) is a key process for the surface preparation of high field superconducting cavities. A portable apparatus for the water jet characterization, based on the transferred momentum between the water jet and a load cell, has been used in different laboratories. This apparatus allows to collected quantitative parameters that characterize the HPR water jet. In this paper, we present a quantitative comparison of the different water jet produced by various nozzles routinely used in different laboratories for the HPR process  
WEPMN026 Test Operation of Ball-Screw-Type Tuner for Low-Loss High-Gradient Superconducting Cavity in a Cryomodule 2104
 
  • T. Higo, F. Furuta, Y. Higashi, T. Saeki, K. Saito, M. Satoh, H. Yamaoka
    KEK, Ibaraki
  
  We are constructing a Superconducting RF Test Facility (STF) at KEK as an R&D for ILC accelerator. In STF, four Low-Loss (LL) type 9-cell cavities will be installed into a cryomodule. We are developing ball-screw-type tuner for these cavities aiming at the accelerating gradient of 45 MV/m. At the end of 2006, we installed one LL 9-cell cavity dressed with the ball-screw tuner into the cryomodule. It will be operated without beam in 2007. This paper describes the results of the first operation of the ball-screw tuner for LL 9-cell cavity in the cryomodule of STF.  
WEPMN036 High Field Performance in Reduced Cross-sectional X-Band Waveguides Made of Different Materials 2119
 
  • K. Yokoyama, Y. Higashi, T. Higo, N. K. Kudo, S. Ohsawa
    KEK, Ibaraki
  
  To study the characteristics of different materials on high-field rf breakdown we designed a simplified waveguide, where the field of 200MV/m is realized at rf power of 100MW. The geometry is transformed from the WR90, where the height and the width are reduced from 10.16 mm to 1mm and from 22.86mm to 14mm, respectively. This paper reports on the high-gradient testing of copper and stainless-steel waveguides. We have observed rf breakdowns by bursts of x-rays, flashes of visible lights and acoustic signals. Frequent breakdowns are observed at about 100MV/m level in copper case and the study on the stainless-steel waveguide will be performed to be compared to that of copper case.  
WEPMS039 High Power Tests of Normal Conducting Single-Cell Structures 2430
 
  • V. A. Dolgashev, C. D. Nantista, S. G. Tantawi
    SLAC, Menlo Park, California
  • Y. Higashi, T. Higo
    KEK, Ibaraki
  
  Funding: This work was supported by the U. S. Department of Energy contract DE-AC02-76SF00515.

We report results of the first high power tests of single-cell traveling-wave and standing-wave accelerating structures. These tests are part of an experimental and theoretical study of RF breakdown in normal conducting structures at 11.4 GHz*. The goal of this study is to determine the gradient potential of normal conducting, RF powered particle beam accelerators. The test setup consists of reusable mode converters and short test structures powered by SLAC?s XL-4 klystron. This setup was created for economic testing of different cell geometries, cell materials and preparation techniques with short turn-around time. The mode launchers and structures were manufactured at SLAC and KEK and tested in the klystron test laboratory at SLAC.

* V. A. Dolgashev et al., "RF Breakdown In Normal Conducting Single-Cell Structures," SLAC-PUB-11707, Particle Accelerator Conference (PAC 05), Knoxville, Tennessee, 16-20 May 2005, pp. 595- 599.

 
WEPMS042 Optimization of the Low-Loss SRF Cavity for the ILC 2439
 
  • Z. Li, L. Ge, K. Ko, L. Lee, C.-K. Ng, G. L. Schussman, L. Xiao
    SLAC, Menlo Park, California
  • T. Higo, Y. Morozumi, K. Saito
    KEK, Ibaraki
  • P. Kneisel
    Jefferson Lab, Newport News, Virginia
  • J. S. Sekutowicz
    DESY, Hamburg
  
  Funding: Work supported by DOE contract DE-AC02-76SF00515.

The Low-Loss shape cavity design has been proposed as a possible alternative to the baseline TESLA cavity design for the ILC. The advantages of this design over the TESLA cavity are its lower cryogenic loss, and higher achievable gradient due to lower surface fields. High gradient prototypes for such designs have been tested at KEK (ICHIRO) and JLab (LL). However, issues related to HOM damping and multipacting (MP) still need to be addressed. Preliminary numerical studies of the prototype cavities have shown unacceptable damping for some higher-order dipole modes if the typical TESLA HOM couplers are directly adapted to the design. The resulting wakefield will dilute the beam emittance thus reduces the machine luminosity. Furthermore, high gradient tests on a 9-cell prototype at KEK have experienced MP barriers although a single LL cell had achieved a high gradient. From simulations, MP activities are found to occur in the end-groups of the cavity. In this paper, we will present the optimization results of the end-groups for the Low-Loss shape for effective HOM damping and alleviation of multipacting. Comparisons of simulation results with measurements will also be presented.

 
THOAKI03 Revision of Accelerating and Damping Structures for KEK STF 45 MV/m Accelerator Modules 2575
 
  • Y. Morozumi, F. Furuta, T. Higo, T. Saeki, K. Saito
    KEK, Ibaraki
  
  KEK is constructing its superconducting RF test facility and installing 1.3 GHz superconducting accelerator structures. Learning from experience with our first 45MV/m 9-cell structures, we have revised accelerating structures as well as higher order mode dampers for improved performance. Problems found in the earlier structures are discussed and solutions are presented. New experimental results will be also reported.  
slides icon Slides  
THPMN027 Status of C-band Accelerator Module in the KEKB Injector Linac 2769
 
  • T. Kamitani, T. Higo, M. Ikeda, K. Kakihara, N. Kudoh, S. Ohsawa, T. Sugimura, T. T. Takatomi, K. Yokoyama
    KEK, Ibaraki
  
  For future upgrade of the KEKB injector linac, components of C-band accelerator module have been developed since 2002. A prototype C-band accelerator module composed of a 50-MW klystron, an RF-pulse compressor and four 1-m long accelerating sections, has been constructed in the present S-band injector linac. It has been operated for 14 months. In a recent beam-acceleration study, it has achieved an energy gain of 151 MeV, which corresponds to an average acceleration field of 39 MV/m.  
THPMN031 Experiment of X-Ray Source by 9.4 GHz X-Band Linac for Nondestractive Testing System 2781
 
  • T. Natsui, K. Dobashi, M. Uesaka, T. Yamamoto
    UTNL, Ibaraki
  • M. Akemoto, S. Fukuda, T. Higo, N. Kudoh, T. T. Takatomi, M. Yoshida
    KEK, Ibaraki
  • F. Sakamoto, A. Sakumi
    The University of Tokyo, Nuclear Professional School, Ibaraki-ken
  • E. Tanabe
    AET Japan, Inc., Kawasaki-City
  
  We are developing a compact X-ray source for Nondestractive Testing (NDT) system. We aim to develop a portable X-ray NDT system by 950 keV X-band linac to realize in-site inspection. Our system has 20 kV electron gun, and accelerate electron beam to 950 keV with 9.4 GHz X-band linac. RF source of this system is 250kW magnetron. Our target spot size and spatial resolution are 1mm. We adopted APS (Alternative Periodic Structure) tube of pi/2 mode for easy manufacturing. It is difficult to realize a high-shunt-impedance for low-energy-cells, which attributes to manufacturing problems. Instead, we use three pi-mode cavities there. Further, we choose the low power magnetron for small cooling system and the low voltage electron gun for small power supply. For the stability of the X-ray yield the system include the Auto Frequency Control (AFC), which detect and tune the frequency shift at the magnetron. We have also performed X-ray generation calculation by the Monte Carlo code of GEANT and EGS to confirm the X-ray source size. We are going to construct the whole system and verify it experimentally. Updated results are presented at the spot.  
THPMN032 Beam Generation and Acceleration Experiments of X-Band Linac and Monochromatic keV X-Ray Source of the University of Tokyo 2784
 
  • F. Sakamoto, T. Natsui, Y. Taniguchi, M. Uesaka, T. Yamamoto
    UTNL, Ibaraki
  • M. Akemoto, T. Higo, J. Urakawa
    KEK, Ibaraki
  • D. Ishida, N. Kaneko, H. Nose, H. Sakae, Y. Sakai
    IHI/Yokohama, Kanagawa
  • M. Yamamoto
    Akita National College of Technology, Akita
  
  In the Nuclear Professional School, the University of Tokyo, we are constructing an X-band linear accelerator that consists of an X-band thermionic cathode RF gun and X-band accelerating structure. This system is considered for a compact inverse Compton scattering monochromatic X-ray source for the medical application. The injector of this system consists of the 3.5-cell coaxial RF feed coupler type X-band thermionic cathode RF gun and an alpha-magnet. The X-band accelerating structure is round detuned structure (RDS) type that developed for the future linear collider are fully adopted. So far, we have constructed the whole RF system and beam line for the X-band linac and achieved 2 MeV electron beam generation from the X-band thermionic cathode RF gun. In addition, we achieved 40 MW RF feeding to the accelerating structure. The laser system for the X-ray generation via Compton scattering was also constructed and evaluated its properties. In this presentation, we will present the details of our system and progress of beam acceleration experiment and the performance of the laser system for the Compton scattering experiment.  
TUPAN045 Beam Operation with Crab Cavities at KEKB 1487
 
  • H. Koiso, T. Abe, T. A. Agoh, K. Akai, M. Akemoto, A. Akiyama, A. Arinaga, K. Ebihara, K. Egawa, A. Enomoto, J. W. Flanagan, S. Fukuda, H. Fukuma, Y. Funakoshi, K. Furukawa, T. Furuya, K. Hara, T. Higo, S. Hiramatsu, H. Hisamatsu, H. Honma, T. Honma, K. Hosoyama, T. Ieiri, N. Iida, H. Ikeda, M. Ikeda, S. Inagaki, S. Isagawa, H. Ishii, A. Kabe, E. Kadokura, T. Kageyama, K. Kakihara, E. Kako, S. Kamada, T. Kamitani, K.-I. Kanazawa, H. Katagiri, S. Kato, T. Kawamoto, S. Kazakov, M. Kikuchi, E. Kikutani, K. Kitagawa, Y. Kojima, I. Komada, T. Kubo, K. Kudo, N. K. Kudo, K. Marutsuka, M. Masuzawa, S. Matsumoto, T. Matsumoto, S. Michizono, K. Mikawa, T. Mimashi, S. Mitsunobu, K. Mori, A. Morita, Y. Morita, H. Nakai, H. Nakajima, T. T. Nakamura, H. Nakanishi, K. Nakao, S. Ninomiya, Y. Ogawa, K. Ohmi, Y. Ohnishi, S. Ohsawa, Y. Ohsawa, N. Ohuchi, K. Oide, M. Ono, T. Ozaki, K. Saito, H. Sakai, Y. Sakamoto, M. Sato, M. Satoh, K. Shibata, T. Shidara, M. Shirai, A. Shirakawa, T. Sueno, M. Suetake, Y. Suetsugu, R. Sugahara, T. Sugimura, T. Suwada, O. Tajima, S. Takano, S. Takasaki, T. Takenaka, Y. Takeuchi, M. Tawada, M. Tejima, M. Tobiyama, N. Tokuda, S. Uehara, S. Uno, Y. Yamamoto, Y. Yano, K. Yokoyama, Ma. Yoshida, M. Yoshida, S. I. Yoshimoto, K. Yoshino
    KEK, Ibaraki
  • E. Perevedentsev
    BINP SB RAS, Novosibirsk
  
  Beam operation with crab cavities is planned in early 2007 at KEKB. The crab crossing scheme is expected to increase the vertical beam-beam tune-shift parameter significantly. One crab cavity will be installed in each ring where conditions for beam optics are matched to compensate the beam crossing angle of 22 mrad. Operation results on collision tuning with the crab cavities will be presented.

For the KEKB Accelerator Group.