Author: Washio, M.
Paper Title Page
MOPMP009 Effect of Initial Parameters on the Super Flat Beam Generation with the Phase-Space Rotation for Linear Colliders 442
 
  • M. Kuriki, R. Tamura
    HU/AdSM, Higashi-Hiroshima, Japan
  • H. Hayano, X.J. Jin, T. Konomi, Y. Seimiya, N. Yamamoto
    KEK, Ibaraki, Japan
  • S. Kashiwagi
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
  • P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • J.G. Power
    ANL, Argonne, Illinois, USA
  • K. Sakaue
    The University of Tokyo, The School of Engineering, Tokyo, Japan
  • M. Washio
    RISE, Tokyo, Japan
  
  Funding: This work is partly supported by Japan-US Cooperative grant for scientific studies, Grant aid for scientific study by MEXT Japan (KAKENHI) Kiban B.
Linear collider is a concept to realize e+e− collision beyond the limitation of the ring colliders by the synchrotron radiation. To obtain an enough luminosity, eg. 1.0·10+34 cm-2sec-1, the beam is focused down to nano-meter size with a high aspect ratio. This super flat beam is useful to improve the luminosity and to compensate the beam-beam effect, eg. Beamstrahlung. In a conventional design, the super-flat beam is produced by radiation damping in a storage ring. We propose to produce this super-flat beam with phase-space rotation techniques. We employ both Round to Flat Beam Transformation and Transverse to Longitudinal Emittance eXchange, the super flat beam can be generated by controlling the space-charge effect which spoiled the performance. We present the RFBT performance with respect to the initial conditions, i.e. beam size, initial emittance, solenoid field (strength and profile), etc. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP009  
About • paper received ※ 13 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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TUPGW032 Mode-Locked Pulse Oscillation of a Self-Resonating Enhancement Optical Cavity 1471
 
  • Y. Hosaka
    QST/Takasaki, Takasaki, Japan
  • Y. Honda, T. Omori, J. Urakawa
    KEK, Ibaraki, Japan
  • A. Kosuge
    ISSP, Kashiwa-shi, Japan
  • K. Sakaue
    The University of Tokyo, The School of Engineering, Tokyo, Japan
  • T. Takahashi
    Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
  • Y. Uesugi
    Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Sendai, Japan
  • M. Washio
    Waseda University, Tokyo, Japan
  
  A power enhancement optical cavity is a compelling means of realizing a pulsed laser with a high peak power and high repetition frequency, which is not feasible using a simple amplifier scheme. However, a precise feedback system is necessary for maintaining the narrow resonance condition of the optical cavity; this has become a major technical issue in developing such cavities. We have developed a new approach that does not require any active feedback system, by placing the cavity in the outer loop of a laser amplifier. We report on the first demonstra-tion of a mode-locked pulse oscillation using the new system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW032  
About • paper received ※ 15 April 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPGW038 Study on Coherent THz Radiation Using Tilt Control of Electron Beam 1489
 
  • Y. Tadenuma, M. Brameld, T. Murakami, K. Sakaue, M. Washio
    Waseda University, Tokyo, Japan
  
  Funding: This work was supported by a research granted from JSPS KAKENHI 17H02821.
The terahertz wave is located in the intermediate frequency band between radio waves and light waves, and researches on the light sources such as terahertz quantum cascade laser and femtosecond laser based THz sources are being conducted*. As a new terahertz light source, we are studying coherent Cherenkov radiation by using the tilt control of electron beam and irradiating the target medium. Since the radiation intensity of Cherenkov radiation depends on the target medium, comparison of three kinds of medium with different refractive index and density, and optimization of the target shape were performed. In addition, we are going to try quasi monochromatization of radiation by using multi slit to control the form factor of the electron beam. In this presentation, we will report the experimental results of target optimization and quasi monochromatization and the future prospects.
*S. S. Dhillon, et al., The 2017 terahertz science and technology roadmap, J. Phys. D: Appl. Phys., 50 (2017) 043001. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW038  
About • paper received ※ 12 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPTS111 Study on Improving Durability of Cs-Te Photocathode for an RF-gun 2182
 
  • T. Tamba, J. Miyamatsu, K. Sakaue, M. Washio
    Waseda University, Tokyo, Japan
  
  At Waseda University, we have been studying for high quality electron beam generation using 1.6 cell Cs-Te photocathode rf-gun. We use photocathode as the electron source, which can generate high- quality electron beam such as low emittance, and short bunch. The performance of photocathode is evaluated mainly in terms of quantum efficiency (Q.E.) and lifetime. Cs-Te photocathode used in the rf-gun is known for high Q.E. about 10% with UV light and relatively longer lifetime among semiconductor photocathodes. Since it is a hard environment for photocathode inside the gun, it is necessary to replace the photocathode every several months. In other words, in order to achieve long-term operation of rf-gun, it is necessary to find highly durable photocathode recipe. It has been reported that the Cs-Te photocathode by co-evaporation can produce a photocathode having a longer lifetime as compared with the sequential evaporation. Moreover, we have done studies to improve lifetime and durability of Cs-Te photocathode by coating the cathode surface with CsBr thin film. In this conference, we report the evaluation results of Cs-Te photocathode by co-evaporation, CsBr coating and future prospects.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS111  
About • paper received ※ 12 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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THPGW035 Development of Yb-Based Laser System for Crab Crossing Laser-Compton Scattering 3657
 
  • R. Morita, Y. Koshiba, S. Ota, M. Washio
    Waseda University, Tokyo, Japan
  • T. Higashiguchi
    Center for Optical Research and Education, Utsunomiya University, Utsunomiya, Japan
  • K. Sakaue
    The University of Tokyo, The School of Engineering, Tokyo, Japan
  • J. Urakawa
    KEK, Ibaraki, Japan
  
  Funding: This work was supported by JSPS KAKENHI 18H0123.
We are going to demonstrate the principle of crab crossing in laser-Compton scattering which creates head-on collision in a pseudo manner to enhance the intensity of laser-Compton X-ray. When the electron beam is tilted by half of the collision angle, the scat-tered X-rays becomes the largest. Calculation shows that more than threefold luminosity will be achieved in our system and could be larger luminosity depending on the beam parameters. The intensity of scattered light can be efficiently enhanced by using a collision laser with high intensity, high quality and ultrashort pulse duration. Thus, we have introduced a regenera-tive amplifier using ceramics thin-disk as a collision laser and developed a dedicated laser system. In this conference, we will report on our laser system and results of crab crossing laser-Compton scattering. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW035  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPGW036 Development of Supercontinuum Light Production System Using Er Fiber Laser for Pulse Radiolysis* 3660
 
  • T. Uchida, S. Hanai, K. Sakaue, M. Washio
    Waseda University, Tokyo, Japan
  
  Pulse radiolysis is one of the methods to elucidate radiation chemical reactions. In order to elucidate that, not only high temporal resolution, but also a light source with a broad spectrum band is required. A Xe flash lamp is mentioned as a light source having a broad spectrum band. However, in measurement using a Xe flash lamp, the time resolution is limited to the nanosecond order. In this research, we have developed supercontinuum light as a light source that enables picosecond time resolution and has a broader spectrum band. In this paper, we developed a light source using an Er doped fiber laser for pulse radiolysis measurement, and report the results and future prospects here.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW036  
About • paper received ※ 15 May 2019       paper accepted ※ 24 May 2019       issue date ※ 21 June 2019  
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