• Y. Tanimoto, T. Honda, S. Sakanaka
  KEK, Ibaraki

Sudden decrease in the beam lifetime is sometimes observed in many electron storage rings. Such an event has been commonly attributed to dust trapping, but its mechanism has not been entirely elucidated yet. Our recent research at PF-AR has shown that trapped dust with certain conditions can be visually observed by video cameras, and the recorded movies revealed that the trapped dust moved longitudinally. In addition, the light emission from the dust indicated that its temperature reached 1000 K or more. Thus, direct observation of trapped dust has been proved to be an effective way to investigate the dust trapping mechanism. We have carried on this research with advanced cameras, such as high-sensitivity or high-speed cameras, and the results will be presented.

• R. Takai, T. Honda, Y. Kobayashi, T.M. Mitsuhashi, T. Obina, M. Shimada, Y. Tanimoto
  KEK, Ibaraki

A hybrid fill mode has been tested at the Photon Factory storage ring (PF-ring). The hybrid fill mode consists of a train of low-current bunches and a high-current single bunch. Since a bunch-by-bunch feedback system was not available because of the high contrast of currents between the bunch train and the single bunch, we suppressed multibunch instabilities in the transverse and longitudinal planes by using the octupole magnets and RF phase modulation, respectively. We also suppressed single-bunch instabilities by controlling ring chromaticity. As a result, we successfully stored a 450 mA current with the hybrid fill mode: 1/2 filling (2.56 mA/bunch × 156) + 1 single bunch opposite to the bunch train (50 mA/bunch). The distribution of vacuum pressures along the ring was similar for the hybrid fill and the typical single-bunch mode. In this conference, we will present the results of this test experiment as well as some future subjects to be solved for the user operation.

• S. Sakanaka, M. Akemoto, T. Aoto, D.A. Arakawa, S. Asaoka, A. Enomoto, S. Fukuda, K. Furukawa, T. Furuya, K. Haga, K. Hara, K. Harada, T. Honda, Y. Honda, H. Honma, T. Honma, K. Hosoyama, M. Isawa, E. Kako, T. Kasuga, H. Katagiri, H. Kawata, Y. Kobayashi, Y. Kojima, T. Matsumoto, H. Matsushita, S. Michizono, T.M. Mitsuhashi, T. Miura, T. Miyajima, H. Miyauchi, S. Nagahashi, H. Nakai, H. Nakajima, E. Nakamura, K. Nakanishi, K. Nakao, T. Nogami, S. Noguchi, S. Nozawa, T. Obina, S. Ohsawa, T. Ozaki, C.O. Pak, H. Sakai, H. Sasaki, Y. Sato, K. Satoh, M. Satoh, T. Shidara, M. Shimada, T. Shioya, T. Shishido, T. Suwada, M. Tadano, T. Takahashi, R. Takai, T. Takenaka, Y. Tanimoto, M. Tobiyama, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, K. Watanabe, M. Yamamoto, S. Yamamoto, Y. Yamamoto, Y. Yano, M. Yoshida
  KEK, Ibaraki
• M. Adachi, M. Katoh, H. Zen
  UVSOR, Okazaki
• R. Hajima, R. Nagai, N. Nishimori, M. Sawamura
  JAEA/ERL, Ibaraki
• H. Hanaki
  JASRI/SPring-8, Hyogo-ken
• H. Iijima, M. Kuriki
  HU/AdSM, Higashi-Hiroshima
• I. Ito, H. Kudoh, N. Nakamura, S. Shibuya, K. Shinoe, H. Takaki
  ISSP/SRL, Chiba
• H. Kurisu
  Yamaguchi University, Ube-Shi
• M. Kuwahara, T. Nakanishi, S. Okumi
  Nagoya University, Nagoya
• S. Matsuba
  Hiroshima University, Graduate School of Science, Higashi-Hiroshima
• T. Muto
  Tohoku University, School of Scinece, Sendai
• K. Torizuka, D. Yoshitomi
  AIST, Tsukuba

Future synchrotron light source using a 5-GeV-class energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting active R&D efforts for that. We are developing super-brilliant DC photocathode guns, two types of cryomodules for both injector and main superconducting linacs, 1.3 GHz high CW-power rf sources, and other important components. We are also constructing a compact ERL for demonstrating the recirculation of low-emittance, high-current beams using those key components. We present our recent progress in this project.

• T. Honda, T. Aoto, S. Asaoka, K. Ebihara, K. Furukawa, K. Haga, K. Harada, Y. Honda, T. Ieiri, N. Iida, M. Izawa, T. Kageyama, M. Kikuchi, Y. Kobayashi, K. Marutsuka, A. Mishina, T. Miyajima, H. Miyauchi, S. Nagahashi, T.T. Nakamura, T. Nogami, T. Obina, K. Oide, M. Ono, T. Ozaki, C.O. Pak, H. Sakai, H. Sakai, Y. Sakamoto, S. Sakanaka, H. Sasaki, Y. Sato, K. Satoh, M. Shimada, T. Shioya, M. Tadano, T. Tahara, T. Takahashi, R. Takai, S. Takasaki, Y. Tanimoto, M. Tobiyama, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, M. Yamamoto, Ma. Yoshida, S.I. Yoshimoto
  KEK, Ibaraki

KEK manages two synchrotron radiation sources, Photon Factory storage ring (PF-ring) of 2.5 GeV and Photon Factory advanced ring (PF-AR) of 6.5 GeV. These rings share an injector linac with the two main rings of KEK B-factory, 8-GeV HER and 3.5-GeV LER. Recently, the linac has succeeded in a pulse by pulse multi-energy acceleration. A top-up operation of PF-ring has been realized as the simultaneous continuous injection to the 3 rings, PF-ring, HER and LER. Development of new injection scheme using a pulsed sextupole magnet continues aiming at practical use in the top-up operation. A rapid-polarization-switching device consisting of tandem two APPLE-II type undulators has been developed at PF-ring. The first undulator was installed in 2008, and the second one will be installed in 2010 summer. PF-AR, operated in a single-bunch mode at all times, has been suffered from sudden lifetime drop phenomena attributed to dust trapping for many years. Using the movable electrodes installed for experiment, we confirmed that the discharge created by the electrode was followed by the dust trapping, and succeeded in a visual observation of luminous dust streaking in front of CCD cameras.