Author: Urakawa, J.
Paper Title Page
MOOCA03 Updates to the International Linear Collider Damping Rings Baseline Design 32
 
  • S. Guiducci, M.E. Biagini
    INFN/LNF, Frascati (Roma), Italy
  • G. Dugan, M.A. Palmer, D. L. Rubin
    CLASSE, Ithaca, New York, USA
  • J. Gao, D. Wang
    IHEP Beijing, Beijing, People's Republic of China
  • M.T.F. Pivi, Y. Sun
    SLAC, Menlo Park, California, USA
  • J. Urakawa
    KEK, Ibaraki, Japan
  
  A new baseline design for the International Linear Collider (ILC) damping rings has been adopted which reduces the ring circumference to 3.2 km from 6.4 km. This design change is associated with a revised plan to operate the ILC with one half the beam current originally specified in the ILC Reference Design Report. We describe the new layout and lattice that has been developed for the shorter ring. In addition, we discuss features of the new design that will allow operation at a 10Hz repetition rate which is twice the rate specified for baseline operation. Finally, we examine the implications for restoring operation with the originally specified beam current while maintaining the smaller ring circumference.  
slides icon Slides MOOCA03 [2.381 MB]  
 
MOPC014 RF Processing of L-band RF Gun for KEK-STF 92
 
  • M. Kuriki, H. Iijima, Y.M. Masumoto
    HU/AdSM, Higashi-Hiroshima, Japan
  • H. Hayano, H. Sugiyama, J. Urakawa, K. Watanabe
    KEK, Ibaraki, Japan
  • G. Isoyama, R. Kato
    ISIR, Osaka, Japan
  • S. Kashiwagi
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
  • Y. Takahashi
    Sokendai, Ibaraki, Japan
  
  Funding: This work is supported by MEXT Quantum Beam Technology Program, KEK Promotion of collaborative research programs in universitie.
KEK STF (Superconducting Test Facility) is established for developing super-conducting accelerator technology for ILC (International Linear Collider). At KEK-STF, accelerator operation with a beam loading is planned in 2013. An electron injector based on L-band Photo-cathode RF gun is now being developed. A L-band RF gun designed by DESY and fabricated by FNAL has been placed in KEK-STF and RF processing was carried out. The results of the RF processing and status of STF injector will be presented. 		 
 
MOPC020 Development of an S-band Multi-cell Accelerating Cavity for RF Gun and Booster Linac 110
 
  • T. Aoki, K. Sakaue, M. Washio
    RISE, Tokyo, Japan
  • A. Deshpande
    SAMEER, Mumbai, India
  • M.K. Fukuda, N.K. Kudo, T. Takatomi, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  
  Funding: Work supported by JST Quantum Beam Program
We have been developing a photocathode rf gun. The rf gun with multi cell can produce a high energy electron beam, so it may be used for numerous applications such as medicine and industry. At Laser Undulator Compact X-ray source (LUCX), we have developed a compact X-ray source based on inverse Compton scattering. Using a multi cell rf gun will make possible for the X-ray source to use for such applications. S-band 3.5 cell rf electron gun which is 20 cm long can produce more than 10 MeV electron beam. According to the simulation, it is said that the emittance of 3.5 cell rf gun is as low as that of 1.6 cell rf gun. The electromagnetic design has been performed with the code SuperFish, and the particle tracing by Parmela. The new rf gun is already installed and produced a high quality electron beam with energy of more than 10 MeV. As a consequence of the substantial efforts of developing rf cavity, we decide to make a compact RF accelerating structure with more cell for achieving a smaller system. The measurement results of using the 3.5 cell rf gun, the design of 12 cell booster cavity, and current status of 12 cell cavity manufacturing will be presented at the conference. 		 
 
MOPC146 Development of Timing Distribution System with Femto-second Stability 421
 
  • T. Naito, K. Ebihara, S. Nozawa, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • M. Amemiya
    AIST, Tsukuba, Japan
  
  A timing distribution system with femto-second stability has been developed for the RF synchronization of accelerator and the laser synchronization of the pump-probe experiments. The system uses a phase stabilized optical fiber(PSOF) and an active fiber length stabilization. The PSOF has 5 ps/km/degC of the temperature coefficient. The active fiber length stabilization uses the phase detection of the round-trip sinusoidal wave and the fiber stretcher for the compensation of the fiber length. In this paper, we present the test results on a 500 m long signal distribution. The preliminary results of the timing stability are 20 fs at several minutes and 100 fs at four days, respectively.  
 
TUPC016 Status of the ATF2 Lattices 1027
 
  • E. Marin, R. Tomás
    CERN, Geneva, Switzerland
  • P. Bambade
    LAL, Orsay, France
  • T. Okugi, T. Tauchi, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • A. Seryi
    JAI, Oxford, United Kingdom
  • G.R. White, M. Woodley
    SLAC, Menlo Park, California, USA
  
  The latest status for the ATF2 Nominal and Ultra-low beta lattices designs obtained to minimize the detrimental effect of the measured multipoles are presented in this paper. A set of correction knobs for the most important aberrations at the IP have been obtained for both lattices in order to perform the tuning under realistic imperfections. Starting from the tuned ATF2 Nominal lattice a squeeze sequence reducing betay is performed to reach the ultra-low beta lattice. Tuning results are shown for both options.  
 
TUPC053 Superconducting Positron Stacking Ring for CLIC 1117
 
  • F. Zimmermann, L. Rinolfi
    CERN, Geneva, Switzerland
  • E.V. Bulyak, P. Gladkikh
    NSC/KIPT, Kharkov, Ukraine
  • T. Omori, J. Urakawa, K. Yokoya
    KEK, Ibaraki, Japan
  
  The generation of polarized positrons for future colliders based on Compton storage rings is a promising method. A challenging key ingredient of this method is the necessary quasi-continuous positron injection into a stacking ring. The ordinary methods of multi-turn injection are not appropriate for this purpose, because the required number of injection-turns is a few hundred, and the emittance of the injected positron bunches is large. This paper describes a possible solution based on 5 GeV superconducting stacking ring, where a novel method of the combined longitudinal and transverse injection process is used to stack positrons. The ring dynamic aperture allows to inject the positron beam with normalized emittance up to 2000 micrometers during a few hundred turns. The injection efficiency is larger than 90% in simulation. The number of the injection turns is only limited by the synchrotron radiation power. The ring lattice and the results of injection simulations are presented.  
 
TUPC057 Femtosecond Photoinjector and Relativistic Electron Microscopy 1126
 
  • J. Yang, K. Kan, Y. Murooka, N. Naruse, K. Tanimura, Y. Yoshida
    ISIR, Osaka, Japan
  • J. Urakawa
    KEK, Ibaraki, Japan
  
  A new rf gun driven by a femtosecond laser has been developed successfully for the relativistic electron diffraction in Osaka University for the study of ultrafast dynamics of intricate molecular and atomic processes in materials. The beam dynamics of femtosecond electron bunch in the rf gun were investigated to achieve a low-emittance and low-energy-spread; i.e. 0.1 mm-mrad and 10-4. A time-resolved relativistic electron microscopy is being developed to reveal the hidden dynamics on the femtosecond and nanometer scales. The same demonstrations of the MeV electron diffraction/imaging measurements were reported.  
 
TUPC058 Design of a Chirping Cell Attached RF Gun for Ultrashort Electron Generation 1129
 
  • K. Sakaue, K. Tamai, M. Washio
    RISE, Tokyo, Japan
  • J. Urakawa
    KEK, Ibaraki, Japan
  
  Funding: Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690
We have been developing an S-band photocathode rf electron gun at Waseda university. Our rf-gun cavity was firstly designed by BNL and then, modified by our group. In this paper, we will introduce a newly designed rf-gun cavity with energy chirping cell. To generate an energy chirped electron bunch, we attached extra-cell for 1.6cell rf-gun cavity. Cavity design was done by Superfish and particle tracing by PARMELA. By optimizing the chirping cell, we observed linear chirped electron bunch. The front electron have lower energy than rear. Then transporting about 2m, the bunch can be compressed down to 200fsec electron bunch with the charge of 160pC. This ultrashort bunch will be able to use for generating CSR THz radiation, pumping some material to be studied by pulse radiolysis method, and so on. In this conference, the design of chirping cell attached rf-gun, the results of tracing simulation and plan of manufacturing will be presented. 		 
 
TUPC059 Study on Energy Compensation by RF Amplitude Modulation for High Intense Electron Beam Generated by a Photocathode RF-Gun 1132
 
  • Y. Yokoyama, T. Aoki, K. Sakaue, T. Suzuki, M. Washio, T. Yamamoto
    RISE, Tokyo, Japan
  • H. Hayano, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • S. Kashiwagi
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
  • R. Kuroda
    AIST, Tsukuba, Ibaraki, Japan
  
  Funding: Work supported by JSPS Grant-in-Aid for Scientific Research(A)10001690 and JST Quantum Beam Program.
At Waseda University, we have been studying a high quality electron beam generation and its application experiments with a Cs-Te photocathode RF-Gun. To generate more intense and stable electron beam, we have been developing the cathode irradiating UV laser which consists of optical fiber amplifier and LD pumped amplifier. As the result, more than 100 multi-bunch electron beam with 1nC each bunch charge was obtained. However, it is considered that the accelerating voltage will decrease because of the beam loading effect. So we have studied the RF amplitude modulation technique to compensate the beam energy difference. The energy difference will caused by transient accelerating voltage in RF-Gun cavity and beam loading effect. As the result of this compensation method, the energy difference has been compensated to 1%p-p, while 5%p-p without compensation. In this conference, we will report the details of energy compensation method using the RF amplitude modulation, the results of beam experiments and the future plans. 		 
 
TUPC158 Micron-scale Laser-wire at the ATF-II at KEK Commissioning and Results 1401
 
  • L.J. Nevay, G.A. Blair, S.T. Boogert, L. Corner, L.C. Deacon, V. Karataev, R. Walczak
    JAI, Oxford, United Kingdom
  • A.S. Aryshev, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  
  We present the first results from the commissioning of the upgraded laser-wire experiment at the Accelerator Test Facility 2 (ATF2) at KEK. A new laser transport line and beam diagnostics were used to collide 150 mJ, 167 ps long laser pulses with 1.28 GeV, 30 ps long electron bunches to measure the vertical transverse size. Additionally, a new detector was installed with a reduced area for lower background. Initial scans showing a convoluted beam size of 19.2 ± 0.2 microns were used to tune the electron beam optics and reduce this down to 8.1 ± 0.1 microns. Laser pulse energy and charge dependency were investigated showing a linear relationship in both with a minimum laser energy of 20 mJ required for observable signal with this laser and setup.  
 
TUPO012 Stable Planner Type Four-mirror Cavity Development for X-ray Production as Basic Development of Quantum Beam Technology Program 1470
 
  • H. Shimizu, Y. Higashi, Y. Honda, J. Urakawa
    KEK, Ibaraki, Japan
  
  As the development of quantum beam technology program, a facility to produce a semi-monochromatic X-ray via inverse Compton scattering with an electron beam accelerated by a superconducting RF cavity and a fiber amplified high power laser stacked in an external optical cavity system are now under construction. To achieve high brightness of Compton X-ray, we introduced a chicane with about a 1m-long zero dispersion straight section that includes IP. Head on collision scheme improves the yield of X-ray, but to do so, a huge and stout external optical cavity system must be needed. According to this demand, we develop a quite tolerable planner type four-mirror cavity with movable mirror mount system. In this paper, results obtained by the cavity construction and also laser development activities are described.  
 
WEOBB01 Sub-micrometer Resolution Transverse Electron Beam Size Measurement System based on Optical Transition Radiation 1964
 
  • A.S. Aryshev, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • S.T. Boogert, V. Karataev
    JAI, Egham, Surrey, United Kingdom
  • D. Howell
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
  
  Optical Transition Radiation (OTR) appears when a charged particle crosses a boundary between two media with different dielectric properties has widely been used as a tool for transverse profile measurements of charged particle beams in numerous facilities worldwide. The resolution of the conventional monitors is defined by the Point Spread Function (PSF) dimension - the source distribution generated by a single electron and projected by an optical system onto a screen. For small electron beam dimensions, the PSF form significantly depends on various parameters of the optical system like diffraction of the OTR tails, spherical and chromatic aberrations, etc. In our experiment we managed to create a system which can practically measure the PSF distribution and using a new self-calibration method we are able to calculate transverse electron beam size. Here we represent the development, data analysis and novel calibration technique of a sub-micrometer electron beam profile monitor based on the measurements of the PSF shape, which OTR visibility is sensitive to micrometer electron beam dimensions.  
slides icon Slides WEOBB01 [2.506 MB]  
 
WEPC051 Effect of Compton Scattering on the Electron Beam Dynamics at the ATF Damping Ring 2127
 
  • I. Chaikovska, C. Bruni, N. Delerue, A. Variola, Z.F. Zomer
    LAL, Orsay, France
  • K. Kubo, T. Naito, T. Omori, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  
  Compton scattering provides one of the most promising scheme to obtain polarized positrons for the next generation of e+e− colliders. Moreover it is an attractive method to produce monochromatic high energy polarized gammas for nuclear applications and X-rays for compact light sources. In this framework a four-mirror Fabry-Perot cavity has been installed at the Accelerator Test Facility (ATF - KEK, Tsukuba, Japan) and will be used to produce an intense flux of polarized gamma rays by Compton scattering. For electrons at the energy of the ATF (1.28GeV) Compton scattering may result in a shorter lifetime due to the limited bucket acceptance. We have implemented the effect of Compton scattering on a 2D tracking code with a Monte-Carlo method. This code has been used to study the longitudinal dynamics of the electron beam at the ATF damping ring, in particular the evolution of the energy spread and the bunch length under Compton scattering. The results obtained are presented and discussed. Possible methods to observe the effect of Compton scattering on the ATF beam are proposed.  
 
WEPZ011 Fast Cooling of Bunches in Compton Storage Rings 2790
 
  • E.V. Bulyak
    NSC/KIPT, Kharkov, Ukraine
  • J. Urakawa
    KEK, Ibaraki, Japan
  • F. Zimmermann
    CERN, Geneva, Switzerland
  
  We propose an enhancement of laser radiative cooling by utilizing laser pulses of small spatial and temporal dimensions, which interact only with a fraction of an electron bunch circulating in a storage ring. We studied the dynamics of such electron bunch when laser photons scatter off the electrons at a collision point placed in a section with nonzero dispersion. In this case of ‘asymmetric cooling', the stationary energy spread is much smaller than under conditions of regular scattering where the laser spot size is larger than the electron beam; and the synchrotron oscillations are damped faster. Coherent oscillations of large amplitude may be damped within one synchrotron period, so that this method can support the rapid successive injection of many bunches in longitudinal phase space for stacking purposes. Results of extensive simulations are presented for the performance optimization of Compton gamma-ray sources and damping rings.  
 
TUPC030 Recommendation for Mitigations of the Electron Cloud Instability in the ILC 1063
 
  • M.T.F. Pivi, L. Wang
    SLAC, Menlo Park, California, USA
  • L.E. Boon, K.C. Harkay
    ANL, Argonne, USA
  • J.A. Crittenden, G. Dugan, M.A. Palmer
    CLASSE, Ithaca, New York, USA
  • T. Demma, S. Guiducci
    INFN/LNF, Frascati (Roma), Italy
  • M.A. Furman
    LBNL, Berkeley, California, USA
  • K. Ohmi, K. Shibata, Y. Suetsugu, J. Urakawa
    KEK, Ibaraki, Japan
  • C. Yin Vallgren
    Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg, Sweden
  
  Funding: Work supported by the Director, Office of Science, High Energy Physics, U.S. DOE under Contract No. DE-AC02-76SF00515.
Electron cloud has been identified as one of the highest priority issues for the ILC Damping Rings (DR). A working group has evaluated the electron cloud effect and instability, and mitigation solutions for the electron cloud formation. Working group deliverables include recommendations for the baseline and alternate solutions for the electron cloud mitigation in various regions of the ILC Positron DR, which is presently assumed to be the 3.2km design. Detailed studies of a range of mitigation options including coatings, clearing electrodes, grooves and novel concepts, were carried out over the previous several years by nearly 50 researchers, and the results of the studies form the basis for the recommendation. The assessments of the benefits or risks associated with the various options were based on a systematic ranking scheme. The recommendations are the result of the working group discussions held at numerous meetings and during a dedicated workshop. The mitigation choices will be also presented in a more detailed report later in 2012. In addition, a number of items requiring further investigation were identified and studies will be carried out at CesrTA and other institutions. 		 
 
TUPC119 A Comprehensive Study of Nanometer Resolution of the IPBPM at ATF2* 1296
 
  • Y.I. Kim, H. Park
    Kyungpook National University, Daegu, Republic of Korea
  • S.T. Boogert
    Royal Holloway, University of London, Surrey, United Kingdom
  • J.C. Frisch, D.J. McCormick, J. Nelson, T.J. Smith, G.R. White, M. Woodley
    SLAC, Menlo Park, California, USA
  • Y. Honda, R. Sugahara, T. Tauchi, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  
  Funding: Work supported in part by Department of Energy Contract DE-AC02-76SF00515.
High-resolution beam position monitors (IPBPMs) have been developed in order to measure the electron beam position at the focus point of ATF2 to a few nanometers in the vertical plane. To date, the IPBPM system has operated in test mode with a highest demonstrated resolution of 8.7 nm in the ATF extraction line during 2008. After expected noise source calculations there still remains 7.9 nm of noise of unexplained origin. We summarize the experimental work on the IPBPM system since this measurement and outline the possible origins of these sources. We then present a study plan to be performed at the ATF2 facility designed to identify and to improve the resolution performance and comment on the expected ultimate resolution of this system. 		 
 
TUPC161 Cavity Beam Position Monitor System for ATF2 1410
 
  • S.T. Boogert, R. Ainsworth, G.E. Boorman, S. Molloy
    Royal Holloway, University of London, Surrey, United Kingdom
  • A.S. Aryshev, Y. Honda, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • F.J. Cullinan, N.Y. Joshi, A. Lyapin
    JAI, Egham, Surrey, United Kingdom
  • J.C. Frisch, D.J. McCormick, J. Nelson, T.J. Smith, G.R. White
    SLAC, Menlo Park, California, USA
  • A. Heo, E.-S. Kim, Y.I. Kim
    KNU, Deagu, Republic of Korea
  
  The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a future high energy lepton linear collider. The ATF2 beam-line is instrumented with a total of 41 high resolution C and S band resonant cavity beam position monitors (BPM) with associated mixer electronics and digitizers. In addition 4 high resolution BPMs have been recently installed at the interaction point, we briefly describe the first operational experience of these cavities in the ATF2 beam-line. The current status of the overall BPM system is also described, with a focus on operational techniques and performance.  
 
TUPO002 High Flux Polarized Gamma Rays Production: First Measurements with a Four-mirror Cavity at the ATF 1446
 
  • N. Delerue, J. Bonis, I. Chaikovska, R. Chiche, R. Cizeron, M. Cohen, P. Cornebise, R. Flaminio, D. Jehanno, F. Labaye, M. Lacroix, Y. Peinaud, L. Pinard, V. Soskov, A. Variola, Z.F. Zomer
    LAL, Orsay, France
  • T. Akagi, S. Miyoshi
    Hiroshima University, Graduate School of Advanced Sciences of Matter, Higashi-Hiroshima, Japan
  • S. Araki, Y. Funahashi, Y. Honda, T. Omori, H. Shimizu, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • E. Cormier
    CELIA, Talence, France
  • T. Takahashi
    Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
  
  Funding: ANR, IN2P3
The next generation of e+/e- colliders will require the production of a very intense flux of gamma rays to allow polarized positrons to be produced in sufficient quantities. To demonstrate that this can be achieved a four-mirror cavity has recently been installed at the Accelerator Test Facility (ATF) at KEK to produce a high flux of polarized gamma rays by inverse Compton scattering. A four-mirror non-planar geometry is used to ensure the polarization of the gamma rays produced. The main mechanical features of the cavity are presented. A fibre amplifier is used to inject about 10W in the high finesse cavity with a gain of 1000. A digital feedback system is used to keep the cavity at the length required for the optimal power enhancement. First preliminary measurements show that on some beam crossings the interactions produce more than 25 photons with an average energy of about 24 MeV. Several upgrades currently in progress are described. 		 
 
THPS095 Q-factor of an Open Resonator for a Compact Soft X-ray Source based on Thomson Scattering of Stimulated Coherent Diffraction Radiation 3657
 
  • A.S. Aryshev, S. Araki, M.K. Fukuda, J. Urakawa
    KEK, Ibaraki, Japan
  • V. Karataev
    JAI, Egham, Surrey, United Kingdom
  • G.A. Naumenko
    Tomsk Polytechnic University, Nuclear Physics Institute, Tomsk, Russia
  • A. Potylitsyn, L.G. Sukhikh, D. Verigin
    TPU, Tomsk, Russia
  • K. Sakaue
    RISE, Tokyo, Japan
  
  High-brightness and reliable sources in the VUV and the soft X-ray region may be used for numerous applications in such areas as medicine, biology, biochemistry, material science, etc. We have proposed a new approach to produce the intense beams of X-rays in the range of eV based on Thomson scattering of Coherent Diffraction Radiation (CDR) on a 43 MeV electron beam. CDR is generated when a charged particle moves in the vicinity of an obstacle. The radiation is coherent when its wavelength is comparable to or longer than the bunch length. The CDR waves are generated in an opened resonator formed by two mirrors. In this report the status of the experiment, the first CDR measurements at the multibunch beam of the LUCX facility and general hardware design will be reported.