Author: Urakawa, J.
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MOPRI030 Basic Design of a 20K C-band 2.6-cell Photocathode RF Gun 658
 
  • T. Tanaka, M. Inagaki, K. Nakao, K. Nogami, T. Sakai
    LEBRA, Funabashi, Japan
  • M.K. Fukuda, T. Takatomi, J. Urakawa, M. Yoshida
    KEK, Ibaraki, Japan
  • T.S. Shintomi
    Nihon University, Tokyo, Japan
  
  Funding: This research was supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
A cryocooled C-band photocathode RF gun operating at 20K is under design at Nihon University. The RF gun is of BNL-type 2.6-cell pillbox cavity with a resonant frequency of 5712 MHz. With high-purity Oxygen-free copper used as the cavity material, the quality factor of the cavity is expected to be approximately 60000 from theoretical prediction of the anomalous skin effect at low temperatures. Considering the cooling capacity, initial operation of the RF gun is assumed at a duty factor of 0.01%. The cavity elements designed for low-power test is in preparation for machining. The low-power test at room temperature is scheduled early spring in 2014 before assembled at KEK by means of diffusion bonding technique. Since it is intended for the basic understanding and measurements of low temperature RF properties, the cavity is not equipped with structures for the photocathode assembling or the RF input coupler. The cavity design and the results of RF properties measured at room temperature before diffusion bonding will be reported. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI030  
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MOPRI039 Ultra-short Electron Bunch Generation using Energy-chirping Cell Attached RF Electron Gun 685
 
  • K. Sakaue, Y. Koshiba, M. Mizugaki, M. Washio
    Waseda University, Tokyo, Japan
  • R. Kuroda
    AIST, Tsukuba, Ibaraki, Japan
  • T. Takatomi, J. Urakawa
    KEK, Ibaraki, Japan
  
  Funding: Work supported by JSPS Grant-in-Aid for Young Scientists (B) 23740203 and Scientific Research (A) 10001690
We have been developing an Energy-Chirping-Cell attached RF electron gun (ECC-RF-Gun) for generating ultra-short electron bunches. ECC-RF-Gun has extra cell at the end of gun cavity in order to chirp the bunch energy. Such a bunch can be compressed by the velocity difference though the drift space. We have already installed it to our accelerator system and successfully observed a coherent synchrotron/transition radiation at 0.3THz. It is clear that the bunch length was short enough to generate 0.3THz, which corresponds to less than 500fs bunch length was achieved if we assume the gaussian shape. In this conference, the principle of ECC-RF-Gun, the recent results of bunch length measurement and future prospective will be presented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI039  
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TUPME002 An Optimization of Positron Injector of ILC 1334
 
  • M. Kuriki, Y. Seimiya
    HU/AdSM, Higashi-Hiroshima, Japan
  • S. Kashiwagi
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
  • T. Okugi, M. Satoh, J. Urakawa
    KEK, Ibaraki, Japan
  
  Funding: This work is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT.
ILC (International Linear Collider) is a future project of high energy physics. In the current baseline design, positron generation by gamma rays from undulator radiation is assumed. However, this approach is totally new and it is very difficult to demonstrate the system prior to the construction because it requires more than 100 GeV beam as the driver. A conventional positron generation (e-driven) has been proposed as a technical backup option. In this method, the technology is well established, but the issue is to obtain an enough amount of positron with a manageable energy deposition on target. We present a result of a systematic study of capture efficiency defined by DR (Damping Ring) acceptance where the beam emittance is reduced by radiation damping. We performed a start-to-end simulation of the positron source of ILC and found that an enough amount of the positron per bunch is obtained with a manageable energy deposition on the production target. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME002  
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WEPRO003 Construction of a Laser Compton Scattered Photon Source at cERL 1940
 
  • R. Nagai, R. Hajima, M. Mori, T. Shizuma
    JAEA, Ibaraki-ken, Japan
  • T. Akagi, Y. Honda, A. Kosuge, J. Urakawa
    KEK, Ibaraki, Japan
  
  A nondestructive assay system of isotopes by quasi-monochromatic gamma-rays and nuclear resonance fluorescence is under development in JAEA. The quasi-monochromatic gamma-rays are generated by laser Compton scattering (LCS) based on energy-recovery linac accelerator and laser technologies. In order to demonstrate the accelerator and laser performance required for the gamma-ray source, an LCS experiment is planned at Compact ERL (cERL) at KEK. A mode-locked fiber laser, laser enhancement cavity, beamline, and experimental hatch are under construction for the LCS experiment. Up-to-date construction status is presented in detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRO003  
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WEPRO056 Development of an Optical Resonant Cavity for the LCS Experiment at cERL 2072
 
  • T. Akagi, Y. Honda, A. Kosuge, J. Urakawa
    KEK, Ibaraki, Japan
  • R. Hajima, M. Mori, R. Nagai, T. Shizuma
    JAEA, Ibaraki-ken, Japan
  
  A nondestructive assay system of isotopes by quasi-monochromatic gamma-rays by laser Compton scattering (LCS) is under development. In order to demonstrate the accelerator and laser performance required for the gamma-ray source, an LCS experiment is planned at Compact ERL (cERL) at KEK. An optical resonant cavity is under construction for the LCS experiment. The new optical cavity is designed by combination of two bow-tie cavities to achieve fast optical polarization switching. The performance of the optical cavity is presented in detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRO056  
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WEPRO103 Femtosecond Time-resolved Transmission Electron Microscopy using an RF Gun 2205
 
  • J. Yang, M. Gohdo, K. Kan, T. Kondoh, K. Tanimura, Y. Yoshida
    ISIR, Osaka, Japan
  • J. Urakawa
    KEK, Ibaraki, Japan
  
  The first prototype of RF gun based relativistic-energy electron microscopy has been constructed at Osaka University to study ultrafast structural dynamic processes in matter. The RF gun driven by a femtosecond laser has generated a 100-fs-pulse MeV electron beam with emittance of 0.1 mm-mrad and energy spread of 10-4. Both the electron diffraction and image measurements have been succeeded in the prototype using the femtosecond electron beam. In the diffraction measurement, an excellent quality of diffraction pattern was acquired with electron number of 106. The single-shot measurement is available in the prototype. In the image measurement, the TEM image was acquired with a total electron number of 108. The magnification was 3,000 times. In the next step, we will reduce further the emittance to increase the beam brightness on the sample, and then improve the spatial resolution to <10 nm.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRO103  
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THPME133 Bunch Length Measurement with 2-Cell RF-Deflector at Waseda University 3556
 
  • T. Takahashi, Y. Nishimura, M. Nishiyama, K. Sakaue, M. Washio
    Waseda University, Tokyo, Japan
  • T. Takatomi, J. Urakawa
    KEK, Ibaraki, Japan
  
  We have been studying on a system to measure the length of electron bunch generated by a photocathode rf electron gun at Waseda University. We adopted the rf-deflector system which can convert the longitudinal distribution to transverse by sweeping the electron bunch. By using HFSS, we optimized the design of the 2 cell rf-deflector which is operating on π-mode, dipole (TM110-like) mode at 2856 MHz. The fabrication and the tuning of the rf deflector have successfully processed. We have installed the rf-deflector in the accelerator system of Waseda University, and performed the measurement of the bunch length. It is confirmed that this rf-deflector has the temporal resolution of 167fs with 700kW supply when the beam energy is 4.8MeV. This means that our rf-deflector system has possibility to measure the ultra-short bunch length. In this conference, the rf-deflector system in Waseda University, the result of the bunch length measurement, the performance of the rf-deflector and the future plan will be reported.
Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 and the Quantum Beam Technology Program of MEXT. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME133  
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THPME159 Double Diffraction Radiation Target Interferometry for Micro-train Beam Diagnostics 3635
SUSPSNE073   use link to see paper's listing under its alternate paper code  
 
  • D.A. Shkitov, A. Potylitsyn
    TPU, Tomsk, Russia
  • A.S. Aryshev, J. Urakawa
    KEK, Ibaraki, Japan
  
  Funding: This work was supported by grant of Russian Ministry of Education and Science program “Nauka” number 2.1799.2011.
Recently our group starts to investigate a feasibility of double diffraction radiation (DR) target interferometry for non-invasive micro-train beam diagnostics at KEK: LUCX facility. Double DR target consists of two metal plates and one of them can be moved relative to another along the beam trajectory. Micro-train beam is a sequence of short electron bunches with sub-ps spacing. As it was shown* double DR target can be used for such a beam diagnostics measuring DR yield versus plates displacement. The obtained tuning curve (interferogram) allows to determine a number of bunches within the micro-train and spacing between them. In order to design a reliable device for this aim we have to take into account different double DR target interferometer plate’s adjustment inaccuracies. These inaccuracies can be as follows: inaccuracies in the mutual adjustment of plates tilt angles to the beam trajectory, outer plate edge shift along the beam trajectory and other. The influence of the bunch form-factor shape is also considered. We investigated double DR target preparation accuracy requirements in order to minimize measurements uncertainties and increase interferometer resolution.
* Skitov D.A. et. al., J. Phys.: Conf. Ser. 517, 012024 (2014). 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME159  
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