KEK, Ibaraki
Beam injections to KEKB and Photon Factory are performed with pulse-to-pulse modulation at 50Hz. Three very different beams are switched every 20ms in order to inject those beams into KEKB HER, LER and Photon Factory (PF) simultaneously. Human operators work on one of those three virtual accelerators, which correspond to three-fold accelerator parameters. Beam charges for PF injection and the primary electron for positron generation are 50-times different, and beam energies for PF and HER injection are 3-times different. Thus, the beam stabilities are sensitive to operational parameters, and if any instability in accelerator equipment occurred, beam parameter adjustments for those virtual accelerators have to be performed. In order to cure such a situation, beam energy and orbit feedback systems are installed that can respond to each of virtual accelerators independently.
KEK, Ibaraki
Akita University, Akita
Profile shape measurements detecting profile slope angle, which corresponds to the differential of the profile shape, have been used for evaluating profile shapes highly precisely. They are hardly affected by scanning error in measurement and considered to have advantages for long distance measurements. Here, profile measurement using a level was adopted for straightness alignment of the KEK e-/e+ injector linac, considering the straightness alignment as a profile shape measurement. The slope angles between the alignment base plates of the linac could be detected with reproducibility of 10 micro-rad (σ) by sequential measurement interval of 1 to 2 m. The reproducibility of the straightness derived from the angle measurements was 42 micrometer (σ) for 69 m of the measurement distance and agreed well with the estimated value based on our error propagation model. These results show that straightness reproducibility of better than 1 mm (2-σ) can be achieved for 500 m of the KEK e-/e+ injector linac by sampling interval of 2m, and for 10 km of the ILC linac by sampling interval of 20 cm.
KEK, Ibaraki
A new laser-based alignment system is under development in order to precisely align accelerator components along an ideal straight line at the KEKB injector linac. The new alignment system is strongly required in order to stably accelerate high-brightness electron and positron beams with high bunch charges and also to keep the beam stability with higher quality towards the next generation of B-factories. A new laser optics with Airy pattern (so-called Airy beam) has been developed and the laser propagation characteristics in vacuum has been systematically investigated at a 82-m-long straight section of a beam line of the injector linac. The laser-based alignment measurement based on the new laser optics has been carried out with a measurement resolution of ±0.1 mm level by using a previously-used laser detection system. The experimental results are reported along with the basic design of the new laser-based alignment system.
KEK, Ibaraki
A new laser-based alignment system is under development at the KEKB injector linac. We are revisiting our alignment system because the previous alignment system has become obsolete. The new alignment system is again required to increase the stability of the electron- and positron-beam injection towards next-generation of B-factories. It is similar to the previous one, which comprises a laser-diode system and quadrant photodetectors installed in vacuum light pipes. A displacement of a girder unit of the accelerating structure can be precisely measured in the direction of the laser-ray trace, where the laser light must stably propagate up to 500-m-long downstream without any orbital and beam-size fluctuation. A novel approach in which a two-beam-interference laser-light propagates in the vacuum light pipe, has been designed to increase the alignment precision based on the quadrant photodetector measurement. The propagating laser spot sizes can be narrowed due to the two-beam interference over the Rayleigh-range limit. The design of the new laser-based alignment system is summarized along with some experimental results in this report.
KEK, Ibaraki
Cryomodule tests of four Tesla-like cavities is under preparation for S1-global project at KEK. An average maximum accelerating gradient (Eacc,max) of four cavities in the vertical tests at 2 K was reached to approximately 25 MV/m. Conditioning of four STF-2 input couplers was carried out at a high power test stand with a 5MW-pulsed klystron. Two types of frequency tuning system with a slide-jack tuner and a piezo tuner is installed at the center or end position of the He jacket. String asssembly of the four cavities will be started in March, and the first cool-down test of the cryomodule is scheduled in June, 2010.
KEK, Ibaraki
A superconducting cavity system has been developing for cERL injector Linac at KEK. Two prototype 2-cell niobium cavities and two prototype input couplers were fabricated. The vertical tests of the cavities at 2 K were carried out to qualify their performance. The rf conditioning of the input couplers were carried out at a high power test stand with a cw-300kW klystron. The results of the cavity performances at high gradients and the conditioning of the input couplers will be presented in this paper.
KEK, Ibaraki
UVSOR, Okazaki
JAEA/ERL, Ibaraki
JASRI/SPring-8, Hyogo-ken
HU/AdSM, Higashi-Hiroshima
ISSP/SRL, Chiba
Yamaguchi University, Ube-Shi
Nagoya University, Nagoya
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
Tohoku University, School of Scinece, Sendai
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.
KEK, Ibaraki
KEKB is an e-/e+ collider for the study of B physics and is also used for machine studies for future machines. The peak luminosity of KEKB, which is the world-highest value, has been still increasing. This report summarizes recent progress at KEKB.
KEK, Ibaraki
The KEK injector linac sequentially provides beams, and transfers them to the following four storage rings: a KEKB low-energy ring (LER) (3.5 GeV/positron), a KEKB high-energy ring (HER) (8 GeV/electron), a Photon Factory ring (PF ring; 2.5 GeV/electron), and an Advanced Ring for Pulse X-rays (PF-AR; 3 GeV/electron). So far, beam injection to the PF ring and PF-AR is carried out twice a day, whereas the KEKB rings are operated in the continuous injection mode (CIM) so that the stored current remains almost constant. The KEK linac upgrade project has been started since 2004 so that the PF top-up and KEKB CIM can be performed at the same time. The aim of this upgrade is to change the linac parameters up to 50 Hz, which is the maximum linac beam repetition rate, by using a multi-energy-linac scheme. This upgrade has been successfully completed. The simultaneous top-up operation for three rings has stably been carried out since this April. We will report the simultaneous top-up injection for the KEKB and PF rings in detail.
KEK, Ibaraki
Fermilab, Batavia
INFN/LASA, Segrate (MI)
DESY, Hamburg
In an attempt at demonstrating an average field gradient of 31.5 MV/m as per the design accelerating gradient for ILC, a program called S1-Global is in progress as an international research collaboration among KEK, INFN, FNAL, DESY and SLAC. The S1-Global cryomodule will contain eight superconducting cavities from FNAL, DESY and KEK. The cryomodule will be constructed by joining two half-size cryomodules, each 6 m in length. The module containing four cavities from FNAL and DESY has been constructed by INFN. The module for four KEK cavities is being modified at present. The assembly of the cryomodules is scheduled from January 2010, and the operation of the system is scheduled from June 2010 at the KEK-STF. In this paper, the construction of the S1-Global cryomodule will be presented.
KEK, Ibaraki
The next generation B-factory 'SuperKEKB' project whose target luminosity is 8 ×1035 cm-2s-1 is under consideration. A 'nano-beam scheme' is introduced to the SuperKEKB. In the scheme, an electron beam (Energy = 7 GeV, Charge = 3-4 nC/bunch, Vertical emittance =2.8 x 10-5 m) and a positron beam (Energy = 4 GeV, Charge = 4 nC/bunch, Vertical emittance = 1.6 x 10-5 m), are required at the end of injector linac. They are quite challenging targets for the present linac. In order to meet the requirements, we will introduce some new components to the linac. They are a photo-cathode RF gun for an electron beam, a positron capture section using new L-band cavities, a newly designed positron-generation target system and a damping ring for a positron beam. This presentation shows a strategy of our injector upgrade.