Author: Urakawa, J.
Paper Title Page
MOPPP004 Further Study on Fast Cooling in Compton Storage Rings 571
  • E.V. Bulyak
    NSC/KIPT, Kharkov, Ukraine
  • J. Urakawa
    KEK, Ibaraki, Japan
  • F. Zimmermann
    CERN, Geneva, Switzerland
  Compton sources can produce gamma-ray photons of ultimate intensity, but suffer from the large recoils experienced by the circulating electrons scattering off the laser photons. We have previously proposed a scheme called asymmetric fast cooling to reduce the beam energy spread in Compton rings. This report presents results of further studies on the fast cooling. In particular, we show that (1) a proper asymmetric setup of the scattering point results in significant reduction of the quantum losses of electrons in Compton rings with moderate energy acceptance, and (2) the optimized pulsed mode of operation in synchrotron-dominated rings enhances the overall performance of such gamma-ray sources. Theoretical results presented are in good accordance with numerical simulations. We discuss the performance of an existing storage ring such as KEK ATF DR equipped with an optical cavity and presently available laser system.  
MOPPP005 Feasibility of THz Source Based on Coherent Smith-Purcell Radiation Generated by Femtosecond Electron Bunches in Super-Radiant Regime 574
  • L.G. Sukhikh, K.P. Artyomov, A. Potylitsyn
    Tomsk Polytechnic University, Tomsk, Russia
  • A.S. Aryshev, J. Urakawa
    KEK, Ibaraki, Japan
  • V. Karataev
    JAI, Egham, Surrey, United Kingdom
  Nowadays there is a big interest to THz radiation that is a promising tool for investigations in material science, in biology, medicine and other fields. THz radiation for users is mostly produced by Light Sources that are big and complex machines. Because of this there are numerous activities in research and development of a compact THz source. One of the trends is based on using different types of radiation generated in coherent regime by short electron bunches. The promising radiation mechanism is coherent Smith-Purcell radiation (CSPR) that has monochromatic angular distribution and that is generated while the bunch travels in a vicinity of a grating. In this report we present simulated characteristics of frequency-locked coherent Smith-Purcell radiation (super-radiant regime) generated by a train of short (hundreds of femtosecond) 10 MeV electron bunches with THz spacing. The simulations are performed for different grating profiles and parameters using existing CSPR models and Particle-in-Cell simulation code. We also discuss the feasibility of the THz source based on CSPR and status of the experiment that is prepared at LUCX facility at KEK after the upgrade.  
TUPPD058 Development of an RF Electron Gun for Ultra-Short Bunch Generation 1536
  • Y. Koshiba, T. Aoki, K. Sakaue, M. Washio
    RISE, Tokyo, Japan
  • T. Takatomi, J. Urakawa
    KEK, Ibaraki, Japan
  At Waseda University, various researches are done using a photocathode rf electron gun with a 1.6 cell cavity. Now we are developing a new rf cavity specialized for producing an ultra-short electron bunch, with the collaboration of High Energy Accelerator Research Organization (KEK). We have used SUPERFISH for designing the new rf cavity and PARMELA for beam tracking. The new rf cavity has an extra cell following the 1.6 cell. The extra cell can chirp the energy of electron bunch so we call it ECC (Energy Chirping Cell). ECC chirp the energy because we shortened the length of iris just before the ECC and also the length of ECC itself. Moreover, electric field in ECC is made to be stronger than others. We have confirmed on PARMELA that ECC rf gun can generate an 100pC electron bunch less than 200fsec with the energy of 4.5MeV at about 2.5m away from the cathode. Such an ultra-short electron bunch enables us to generate a coherent terahertz light using ultra-short electron bunch by synchrotron radiation or transition radiation. In this conference, we would like to introduce the detail of the design of this new ECC rf gun, the present progresses and future prospects.  
WEOBB02 Refraction Contrast Imaging via Laser-Compton X-Ray Using Optical Storage Cavity 2146
  • K. Sakaue, T. Aoki, M. Washio
    RISE, Tokyo, Japan
  • M.K. Fukuda, Y. Honda, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  We have been developing a pulsed-laser storage technique in a super-cavity for a compact x-ray sources. The pulsed-laser super-cavity enables to make high peak power and small waist laser at the collision point with the electron beam. Recently, using 357 MHz mode-locked Nd:VAN laser pulses which stacked in a super-cavity scattered off a multi-bunch electron beam, we obtained a multi-pulse x-rays through the laser-Compton scattering. Then, we performed a X-ray imaging via laser-Compton X-ray. The images have edge enhancement by refraction contrast because the X-ray source spot size was small enough. This is one of the evidences that laser-Compton X-ray is high quality. Our laser-Compton experimental setup, the results of X-ray imaging and future prospective will be presented at the conference.  
slides icon Slides WEOBB02 [4.393 MB]  
WEPPP090 Stable RF Distribution System for the S-band Linac 2924
  • T. Naito, K. Ebihara, S. Nozawa, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • M. Amemiya
    AIST, Tsukuba, Japan
  The phase stabilization of the RF phase is key issue for the stable linac operation. An RF distribution system with femto-second stability has been developed for S-band linac using optic fiber links. The system uses a phase stabilized optical fiber (PSOF) and an active fiber length stabilization.* The phase stability is 0.1 degree (100f s) for 24 hours observation. In this paper, we present the test results of the system stability and evaluation of the existing RF reference line by using this system.
* Naito et. al. IPAC10 MOPC146
TUPPD034 Multi-bunch Beam Generation by Photo-cathode RF Gun for KEK-STF 1479
  • M. Kuriki, S. Hosoda, H. Iijima
    HU/AdSM, Higashi-Hiroshima, Japan
  • A. Ayaka
    Sokendai, Ibaraki, Japan
  • H. Hayano, J. Urakawa, K. Watanabe
    KEK, Ibaraki, Japan
  • G. Isoyama, R. Kato, K. Kawase
    ISIR, Osaka, Japan
  • S. Kashiwagi
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
  • K. Sakaue
    RISE, Tokyo, Japan
  Funding: MEXT, Quantum beam project.
KEK-STF is doing R&D of Super-Conducting (SC) accelerator technology for ILC (International Linear Collider), based on 1.3 GHz RF system. For STF and ILC, the pulse length is 1ms and the repetition is 5Hz. We developed a L-band Normal-Conducting RF gun designed by DESY to provide electron beam over such long pulse duration. For NC Photo-cathode RF gun, such high duty and long pulse operation is a challenging task, because the detuning by the heat load of cavity dissipation power is significant. The RF gun provides the electron pulse train to SC accelerator modules which will be operated at 31.5 MV/m gradient. Precise RF control is essential for SC accelerator because the beam loading and input RF power should be well ballanced for a stable operation. The beam test to demonstrate the stable opeation is very important for SC accelerator R&D. The system is also used to demonstrate high-flux quasi-monochromatic X-ray generation by inverse Compton scattering at KEK-STF. The experiment is carried out from April 2012 to November 2012 at KEK-STF. We report the latest status of the multi-bunch generation by the RF gun.
WEPPD055 Gamma-rays Generation with 3D 4-mirror Cavity for ILC Polarized Positron Source 2645
  • T. Akagi, S. Miyoshi
    Hiroshima University, Graduate School of Advanced Sciences of Matter, Higashi-Hiroshima, Japan
  • S. Araki, Y. Funahashi, Y. Honda, T. Okugi, T. Omori, H. Shimizu, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • H. Kataoka, T. Kon
    Seikei University, Japan
  • M. Kuriki, T. Takahashi
    Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
  • K. Sakaue, M. Washio
    RISE, Tokyo, Japan
  • R. Tanaka, H. Yoshitama
    Hiroshima University, Higashi-Hiroshima, Japan
  We are conducting gamma-rays generation experiment by the laser-Compton scattering using a Fabry-Perot cavity. We developed a 3D 4-mirror cavity, and it is installed at the KEK-ATF. By using a 3D 4-mirror cavity, small laser spot can be achieved with stable resonant condition. In addition, we aim 1900 times enhancement of input laser power by a 4-mirror cavity to increase the number of gamma-rays.  
FRXBB01 Femtosecond Electron Guns for Ultrafast Electron Diffraction 4170
  • J. Yang, K. Kan, T. Kondoh, N. Naruse, K. Tanimura, Y. Yoshida
    ISIR, Osaka, Japan
  • J. Urakawa
    KEK, Ibaraki, Japan
  This talk should describe the development of electron guns for producing femtosecond electron pulses with low (<0.1 micron) emittance, for ultrafast electron diffraction. Comparisons should be made between the systems developed by groups in Asia, Europe and America, outlining any similarities and contrasts. The focus should be on the technology for generating, accelerating, and controlling the bunches, but some description of the science applications should also be included. Finally, prospects for future developments should be considered.  
slides icon Slides FRXBB01 [7.004 MB]