KEK, Ibaraki
SLAC, Menlo Park, California
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 design of the S1-G cryomodule began at May 2008 by INFN and KEK. The S1-Global cryomodule was designed to contain eight superconducting cavities from FNAL, DESY and KEK, and to be constructed by joining two half-size cryomodules, each 6 m in length. The module containing four cavities from FNAL and DESY was constructed by INFN. Four KEK cavities have been assembled in the 6 m module which KEK fabricated. All major components were transported to KEK from INFN, FNAL and DESY in December 2009. The assembly of the two 6-m cryomodules started from January 2010 in a collaborative work of FNAL, DESY, INFN and KEK. The construction of the S1-G cryomodule will complete in May, and the cool-down of the S1-G cryomodule is scheduled from June 2010 at the KEK-STF. In this paper, the construction and the cold tests of the S1-Global cryomodule in the worldwide research collaboration will be presented.
KEK, Ibaraki
The KEKB-factory will be upgraded for 40 times higher lumnosity (SuperKEKB). The injector linac is required to increase the beam intensities (e-:1nC -> 5nC, e-:1nC -> 4nC) and reduce the emittances (e-:300 -> 20 um, e+: 2100 -> 10 um ) for the SuperKEKB. A photo-cathode RF gun will be introduced to generate the high-intensity and low-emittance electron beams. A positron damping ring will be constructed to reduce the emittance. A new matching device (a flux concentrator or a superconducing magnet) and an L-band capture section will be introduced to increase the positron intensity. Beam line layout down to the damping ring will be rearranged to have sufficient beam acceptance considering the positron emitttance. This paper describes details of the upgrade scheme of the injector linac.
KEK, Ibaraki
Development of the superconducting injector Linac for compact ERL has been continuing at KEK. The cryomodule including three two-cell SC cavities was designed. Two prot-type two-cell cavities were fabricated, and the vertival test were carried out after the standard surface preparation at STF. The high power tests of the input couplers were also carried out at the test stand with 300 kW cw klystron. The status of the cERL injector cryomodue will be reported.
KEK, Ibaraki
Cryomodule tests of four Tesla-like superconducting cavities is under preparation in the S1-Global project at KEK. Assembly of the cryomodule was started in January 2010, and the installtion in the STF tunnel was completed in April. First cool-down tests are scheduled in June. The low rf power tests of the Tesla-like cavities will be carried out in July. The high rf power tests are scheduled between September and December, 2010.
KEK, Ibaraki
The KEK injector linac sequentially provides beams to 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 had been carried out twice a day, whereas the KEKB rings had been operated in the continuous injection mode (CIM) for keeping stored currents almost constant. The KEK linac upgrade project has started since 2004 so that the PF top-up and KEKB CIM can be operated at the same time. The goal is to inject the beams of different energy into the three independent rings in every 20 ms, where the common DC magnet settings are utilized for beams having different energy and charge, whereas different optimized rf phases are applied to each beam acceleration by using a fast low-level rf control up to 50 Hz. With this noble operation scheme, a simultaneous top-up operation for different three rings was achieved for the first time over the world, and has been stably in operation since last April. We report the operation scheme and status in detail.
KEK, Ibaraki
MHI#10 and #11 cavities are measured in KEK-STF as the s0 plan for ILC. After these vertical tests, they will be sent to J-Lab and tested at least once there. Moreover, two new cavities without HOM coupler are fabricated and measured in STF, which are made by two new vendors (HITACHI and TOSHIBA). As the international collaboration, one cavity from IHEP in Beijing will be sent to KEK, optical inspected, high pressure rinsed and vertical tested. Although MHI#8 cavity for S1-Global reached 38MV/m, it could not achieve ILC specification (35MV/m, 0.8x109) due to the heavy field emission. To overcome this problem, the various tests were done in the stage of the surface treatment. For example, the EP parameters and the rinsing procedure were changed. In this report, the recent results of the vertical tests including the surface treatment in KEK-STF will be presented in detail.
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 towards the next generation of B-factories. A new laser optics generating so-called Airy beam has been developed for the laser-based alignment system. The laser-beam propagation characteristics both in vacuum and at atmospheric pressure have been systematically investigated at a 82-m-long straight section of the injector linac. The results in the measured propagation characteristics are in good agreement with those analyzed on the basis of theoretical analysis in Gaussian laser propagation. In this report the experimental study is described in detail along with the basic design and recent development of the new laser-based alignment system.
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. The new laser-based alignment system consists of the LD mounted on auto stage, vacuum duct, photo diode (PD) and PD detector. To eliminate the laser beam size dependent response of PD, the collimated laser beam propagation along the linac (around 500-m-long) is strongly required. In this paper, we will report the design of collimated laser beam optics for the KEKB injector linac alignment system in detail.