KEK, Ibaraki
A few issues on the path of the luminosity upgrade of KEKB B-Factory is described, including coherent synchrotron radiation, design of the interaction region, crab crossing, and high current operation. These issues will raise more obstacles on the upgrade with the High-Current Scheme. As an alternative, {¥it Nano-Beam Scheme} should be considered as a possible option for the upgrade.
KEK, Ibaraki
KEKB is a multi-bunch, high-current electron-positron collider. Newly installed crab cavities realized an effective head-on collision, while maintaining finite-angle crossing orbits. Bunches form a single train followed by a beam abort gap. We observed a beam phase advancing along a train due to transient beam loading. Since there is a difference in the beam phase between the two beams, a longitudinal displacement of the collision vertex is expected under the crabbing collision. Estimated variations agree with those detected by the Belle*. A displacement in the horizontal beam position was observed in correspondence with the variations in the beam phase. We found that the horizontal displacement was caused by a transverse kick of the crab cavities to phase-shifted bunches. Moreover, a rapid phase advancing was observed at the leading part in a train in the LER. We suspect that some longitudinal wakes with low Q values in accelerator components might contribute to the rapid change in the beam phase.
*H. Kichimi et al., to be published.
KEK, Ibaraki
JAEA/ERL, Ibaraki
JASRI/SPring-8, Hyogo-ken
ISSP/SRL, Chiba
UVSOR, Okazaki
HU/AdSM, Higashi-Hiroshima
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
AIST, Tsukuba
Future synchrotron light source project using an energy recovery linac (ERL) is under proposal at the High Energy Accelerator Research Organization (KEK) in collaboration with several Japanese institutes such as the JAEA and the ISSP. We are on the way to develop such key technologies as the super-brilliant DC photo-injector and superconducting cavities that are suitable for both CW and high-current operations. We are also promoting the construction of the Compact ERL for demonstrating such key technologies. We report the latest status of our project, including update results from our photo-injector and from both superconducting cavities for the injector and the main linac, as well as the progress in the design and preparations for constructing the Compact ERL.
KEK, Ibaraki
MELCO SC, Tsukuba
JAEA, Ibaraki-ken
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
J-PARC, KEK & JAEA, Ibaraki-ken
Beam commissioning of the J-PARC MR has been going on from May 2008. The beam was one bunch of 4·1011 protons, nearly one hundredth of the design value. Here describe performances of the beam diagnostic devices: DCCT's, BPM's, BLM's, profile monitors and tune meters. Diagnostic design for the design intensity will be also included.
KEK, Ibaraki
Crab cavities were installed at KEKB at the beginning of 2007. The beam operation with the crab cavities is in progress. In this paper, machine performance with crab crossing is described focusing on a specific luminosity and a beam lifetime issue related to the dynamic beam-beam effects.