| Paper | Title | Page |
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| MOPAN041 | Design of a Movable Synchrotron Radiation Mask with SiC Absorber for the Photon Factory Advanced Ring (PF-AR) | 248 |
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| We have six rf cavities in the Photon Factory Advanced ring (PF-AR) at KEK. Three years ago, one of them was seriously damaged by the Synchrotron Radiation (SR) from the upstream of the cavity. In order to protect the cavities from SR, we intend to install SR masks nearby the cavities. The masks have to be positioned as close as possible to the beams in order to block the SR completely during the beam storage, and as far as possible during the beam injection. Therefore SR masks should be movable. Since it is placed under strong HOM power from the cavities, careful design is necessary for power dissipation. The basic structure of the movable masks is a coaxial wave-guide with cylindrical SiC absorber whose power capability is designed to be more than 1kW. We report the design of the movable SR masks and the result of rf power test. | ||
| TUPMN046 | Quadrupole HOM Damping with Eccentric-fluted Beam Pipes | 1022 |
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| HOM damping is important for superconducting cavities, especially for high current CW machines such as ERLs. The lower Q-values of HOMs lead to the lower requirement of a refrigerator system and the higher beam current against HOM BBU. Enlarged beam pipes, which have lower cutoff frequencies, are effective to damp HOMs of monopole and dipole, but insufficient for HOMs of quadrupole which have high cutoff frequencies. An eccentric-flute is proposed to damp the HOMs of quadrupole. The eccentric-flute is formed by displacing the flute from the center of the beam pipe and/or by jackknifing around the midpoint of the flute to couple two degenerate modes. The eccentric-flute acts as a mode converter from quadrupole to dipole of the lower cutoff frequency so that the RF power can propagate through the beam pipe. The result of calculation with MAFIA and measurement of a cold model with the eccentric-flute are presented. | ||
| WEPMN034 | Classification of Eigenmodes in a Side-Coupled Structure According to the Space Group Representations | 2116 |
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The geometric symmetry of an rf structure can be expressed by a group of symmetry operations that keep the configuration unchanged*. In case of a periodic rf structure, the symmetry group is a space group containing translations as well as the other symmetry operations. The eigenmodes in the structure can be classified according to the irreducible representations of the space group of the structure. In this paper, this procedure is described with an example of the side-coupled structure (SCS)**. Since the SCS is symmetric under a screw (rotation followed by a non-primitive translation) and a glide operations, it provides a good example of non-symmorphic space group, that is, the group contains an essential screw or glide operations.
* S. Sakanaka, Phys. Rev. ST Accel. Beams 8, 072002 (2005).** E. A. Knapp, B. C. Knapp, and J. M. Potter, Rev. Sci. Instrum. 39, 979 (1968). |
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| TUPMN044 | Status of R&D Efforts Toward the ERL-based Future Light Source in Japan | 1016 |
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| Energy Recovery Linacs (ERL), based on superconducting accelerators, are one of the most promising synchrotron light sources in future. The KEK and the JAEA, in collaboration with the ISSP, the UVSOR, and the SPring-8, are considering to realize together the ERL-based next-generation light source in Japan. To establish key technologies for that, active R&D efforts started. The R&D program includes the developments of ultra-low-emittance photocathode guns and of superconducting cavities, as well as experimental proofs of accelerator-physics issues at the ERL test facility, which will be built at the KEK campus. We are currently working on constructing a prototype photocathode gun, on designing superconducing cavities, and on designing a prototype ERL. The current plan of the prototype ERL comprises a full injector linac, one or two cryomodules for the main linac, and the beam return loop, which can be operated at beam energies from 60 to 160 MeV. The up-to-date R&D status will be reported. | ||
| TUPMN045 | PF-Ring and PF-AR Operational Status | 1019 |
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| In KEK, we have two synchrotron light sources which were constructed in the early 1980s. One is the Photon Factory storage ring (PF-ring) and the other is the Photon Factory advanced ring (PF-AR). The PF-ring is usually operated at 2.5 GeV and sometimes ramped up to 3.0 GeV to provide photons with the energy from VUV to hard X-ray region. The PF-AR is mostly operated in a single-bunch mode of 6.5 GeV to provide pulsed hard X-rays. Operational performances of them have been upgraded through several reinforcements. After the reconstruction of the PF-ring straight sections from March to September 2005, two short-gap undulators were newly installed. They allow us to produce higher brilliant hard X-rays even at the energy of 2.5 GeV. At present we are going to prepare a top-up operation for the PF-ring. In the PF-AR, new tandem undulators have been operated in one straight section since September 2006 to generate much stronger pulsed hard X-rays for the sub-ns resolved X-ray diffraction experiments. In this conference, we report operational status of the PF-ring and the PF-AR including other machine developments. | ||
| FRPMN039 | Measurement of Quadrupolar Tune Shifts After the Reconstruction of the Photon Factory Storage Ring | 4039 |
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The tune shift of transverse quadrupolar oscillations is a measure of a quadrupolar component of wakefields in the storage ring*. By measuring both dipolar and quadrupolar tune shifts, one can estimate the dipolar and the quadrupolar components of wakefields (exactly, kick factors) independently. We carried out such measurements before and after the upgrade of the Photon Factory storage ring. The results showed the change in the tune shifts which were caused by the replacement of many (about two-thirds of the ring) vacuum chambers.
* S. Sakanaka, T. Mitsuhashi, and T. Obina, Phys. Rev. ST Accel. Beams 8, 042801 (2005). |