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Mochihashi, A.

Paper Title Page
MOPCH004 Coherent Harmonic Generation Experiment on UVSOR-II Storage Ring 50
 
  • M. Labat
    CEA, Gif-sur-Yvette
  • M.-E. Couprie
    SOLEIL, Gif-sur-Yvette
  • T. Hara
    RIKEN Spring-8 Harima, Hyogo
  • M. Hosaka, M. Katoh, A. Mochihashi, M. Shimada, J. Yamazaki
    UVSOR, Okazaki
  • G. Lambert
    RIKEN Spring-8, Hyogo
  • D. Nutarelli
    LAC, Orsay
  • Y. Takashima
    Nagoya University, Nagoya
 
  Harmonic Generation schemes on Free Electron Laser devices are very promising. The injection of a traditional laser source inside the first undulator leads to an efficient energy modulation of the electron bunch, and therefore, its spatial modulation, resulting in a more coherent light emission along the second undulator. Experiments have been performed on the UVSOR-II Storage Ring at Okazaki (Japan) with electrons stored at an energy of 600 MeV, and using a 2.5 mJ Ti:Sa laser at 800 nm wavelength, 1 kHz repetition rate, and 100 fs up to 2 ps pulse duration. The experimental setup is presented, including the transport alignment and synchronisation between the laser and the electron beam. The third harmonic at 266 nm has been characterised versus various parameters: current, RF cavity voltage, undulator gap, magnetic functions of the storage ring, and laser pulse duration. Those results are compared with theory via analytical models and simulations.  
TUPCH109 Ion-related Phenomenon in UVSOR/UVSOR-II Electron Storage Ring 1265
 
  • A. Mochihashi, K. Hayashi, M. Hosaka, M. Katoh, J. Yamazaki
    UVSOR, Okazaki
  • Y. Hori
    KEK, Ibaraki
  • Y. Takashima
    Nagoya University, Nagoya
 
  A vertical betatron tune shift depending on beam current under multibunch condition was observed in the UVSOR storage ring. Vertical tune increased as beam current decreased, and the slope of the tune shift depended on the condition of the vacuum in the ring. Such a change in vertical tune was explained by a change in the stability condition of trapped ions*/** with the beam current. Based on a theoretical model*** that gives density of the trapped ions the experimental results were discussed via analytic and tracking calculations. Both the effect from the residual gas ions generated by scattering between high energy electrons and molecules and that from dissociated ions that come from secondary ionization processes have been discussed. In quest of the ion-related phenomenon in single-bunch condition, precise tune measurement has been also performed in the UVSOR-II storage ring. The experimental results in the single-bunch condition have been discussed. Precise measurement of vacuum pressure in the beam duct is a key issue of the ion-related phenomenon. A design of vacuum pressure measurement system via detecting residual gas fluorescence will be introduced in the presentation.

*R. D. Kohaupt. DESY Internal. Bericht No.H1-71/2 (1971). **Y. Baconnier and G. Brianti. CERN Internal Report No.CERN/SPS/80-2(DI) (1980). ***A. Mochihashi et al. Jpn. J. Appl. Phys. 44 (2005) 430.

 
TUPCH110 Upgrade of Main RF Cavity in UVSOR-II Electron Storage Ring 1268
 
  • A. Mochihashi, K. Hayashi, M. Hosaka, M. Katoh, J. Yamazaki
    UVSOR, Okazaki
  • H. Suzuki
    Toshiba, Yokohama
  • Y. Takashima
    Nagoya University, Nagoya
 
  The UVSOR electron storage ring, which is dedicated to a synchrotron radiation (SR) light source especially for VUV and Soft X-ray, has been improved at the beginning of 2003, and transverse emittance in the improved ring (UVSOR-II)* has been decreased from 165nm-rad to 60 and/or 27nm-rad. Users runs have been performed since September 2003 with 60nm-rad mode, and since then high brilliant SR beams have been supplied routinely for users. The 27nm-rad mode, however, was difficult to introduce to daily operation initially because Touschek lifetime was insufficient in such small emittance condition. To improve the beam lifetime and make full use of the SR beams, we have built new main RF cavity. The aim of the improvement was to increase momentum acceptance by increasing RF accelerating voltage; the previous cavity generated the voltage of 55kV, whereas the new one can generate 150kV in maximum without changing RF frequency (90.1MHz) and transmitter (20kW in maximum). The new cavity has been installed in the UVSOR-II in spring of 2005, and high power commissioning went on smoothly. Because of the improvement, from spring 2005 the UVSOR-II has switched the daily users run to 27nm-rad.

*M. Katoh et al., in this conference.

 
THPLS040 Present Status of the UVSOR-II 3374
 
  • M. Katoh, K. Hayashi, M. Hosaka, A. Mochihashi, J. Yamazaki
    UVSOR, Okazaki
  • T. Hara
    RIKEN Spring-8 Harima, Hyogo
  • M. Shimada
    KEK, Ibaraki
 
  UVSOR electron storage ring, which was a 2nd-generation synchrotron radiation (SR) light source for VUV and soft x-ray region, has been renewed as UVSOR-II at the beginning of 2003. Because of the improvement, the beam emittance has been reduced from 165nm-rad to 27nm-rad, and longer straight sections with smaller vertical betatron functions have been provided. In addition to a helical/linear undulator, two in-vacuum undulators have been installed in the long straight sections at the improvement. New variably polarized undulator will be also installed in summer 2006. Improvement of booster synchrotron will be also performed in summer 2006 with aiming to top-up operation in the future. Now UVSOR-II has been operated in 750MeV with the emittance of 27nm-rad in daily users runs. Not only the development of high quality SR beams but also basic investigations for new light source have been performed; development of storage ring FEL and investigation of intense THz burst SR. Bunch slicing experiment with a Ti:Sa laser (800nm) has also been started since 2005, and experiments for coherent harmonic generation and coherent SR generation with the laser-beam interaction have been performed.  
THPLS041 Observation of Intense Terahertz Synchrotron Radiation produced by Laser Bunch Slicing at UVSOR-II 3377
 
  • M. Katoh, M. Hosaka, K. Kimura, A. Mochihashi, M. Shimada
    UVSOR, Okazaki
  • T. Hara
    RIKEN Spring-8 Harima, Hyogo
  • T. Takahashi
    KURRI, Osaka
  • Y. Takashima
    Nagoya University, Nagoya
 
  We have performed electron bunch slicing experiments using a femto-second high power pulse laser in the UVSOR-II electron storage ring. As the pulse laser system we have used a Ti:Sa laser whose wavelength is 800 nm, typical pulse duration is 100 fs, pulse repetition is 1 kHz and typical average power is 2W. The laser is operated in mode-locked condition and synchronized with the electron beam revolution. The laser pulse is injected into an undulator section and it goes along with the electron bunch. By adjusting the radiation wavelength of the undulator to the laser wavelength, the electron beam energy can be partially modulated in the electron bunch. We have observed THz synchrotron radiation (SR) light from a bending magnet that is downstream of the interaction region. The SR light contains extremely intense THz pulse radiation that is synchronized with the laser injection. The extremely high intensity strongly suggests that the THz pulses are coherent synchrotron radiation from the electron bunch with a hole because of the laser-beam interaction.  
THPLS042 Observation of THz Synchrotron Radiation Burst in UVSOR-II Electron Storage Ring 3380
 
  • A. Mochihashi, M. Hosaka, M. Katoh, K. Kimura, M. Shimada
    UVSOR, Okazaki
  • T. Takahashi
    KURRI, Osaka
  • Y. Takashima
    Nagoya University, Nagoya
 
  Very intense THz synchrotron radiation bursts have been observed in single-bunch operation in the UVSOR-II electron storage ring*. The observation was performed in an infrared beam line in UVSOR-II by using a liquid-He-cooled In-Sb hot-electron bolometer that has a good response time of several microseconds. Thanks both to the beam line and the detector, it is clearly observed that the intense bursts have typical macroscopic and microscopic temporal structure. Macroscopically, it is clearly observed that the bursts tend to be generated with quasi-periodic structure in which the period tends to depend on the beam intensity. From a microscopic point of view, each burst has also quasi-periodic structure in itself, and the period almost corresponds to the half value of the inverse of the synchrotron oscillation frequency. The peak intensity of the bursts was about 10000 times larger than that of ordinary synchrotron radiation in the same wavelength region. The extremely high intensity strongly suggests that the bursts are coherent synchrotron radiation, although the radiation wavelength was much shorter than the electron bunch length.

*Y. Takashima et al., Jpn. J. Appl. Phys. 44, No.35 (2005) L1131.