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| MOZAKI01 | Compensation of the Crossing Angle with Crab Cavities at KEKB | 27 |
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The crab cavities are presently being installed in the KEKB rings to compensate the crossing angle at collision and thus increase luminosity. This will be the first experience with such cavities in colliders. Results on the beam operation of the new cavities, both for single and colliding beams, will be presented including the luminosity performance and limitations.
Work presented on behalf of the KEKB Accelerator Group. |
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Slides | |
| TUPMN042 | Simulation Study of Resistive-wall Beam Breakup for ERLs | 1010 |
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For future ERL-based light sources, average beam current is required to be up to 100 mA. Such a high-current multi-bunch beam may generate and cumulate strong long-range wake-fields by interaction with accelerator components such as superconducting cavities and vacuum ducts, and as a result, strong beam breakup(BBU) may occur. Resistive-wall BBU due to narrow and resistive vacuum ducts has been hardly studied, though the effects of BBU due to HOMs of superconducting cavities were much investigated. Asymptotic expressions of transverse resistive-wall BBU were derived for a beam that passes through a uniform resistive pipe under uniform external focusing*. However the expressions are valid only for limited parameter ranges and initial conditions. Therefore we have developed a computer simulation program to study transverse multi-bunch resistive-wall BBU more minutely and generally. In this paper, we will present the simulation results obtained by the simulation program and also compare them with the asymptotic expressions.
* J. M. Wang and J. Wu, PRST-AB 7, 034402(2004) |
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| 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. | ||
| 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. | ||
| TUPAN045 | Beam Operation with Crab Cavities at KEKB | 1487 |
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Beam operation with crab cavities is planned in early 2007 at KEKB. The crab crossing scheme is expected to increase the vertical beam-beam tune-shift parameter significantly. One crab cavity will be installed in each ring where conditions for beam optics are matched to compensate the beam crossing angle of 22 mrad. Operation results on collision tuning with the crab cavities will be presented.
For the KEKB Accelerator Group. |