M. Suetake

The KEKB injector linac

Abstract An 8-GeV electron/3.5-GeV positron injector for KEKB was completed in 1998 by upgrading the existing 2.5-GeV electron/positron linac. The main goals were to upgrade its accelerating energy from 2.5 to 8 GeV and to increase the positron intensity by about 20 times. This article describes not only the composition and features of the upgraded linac, but also how these goals were achieved, by focusing on an optics design and commissioning issues concerning especially high-intensity single-bunch acceleration to produce positron beams.

RF systems for the KEK B-Factory

This paper describes the design features and operational status of the RF systems for the KEK B-Factory (KEKB). Two types of new RF cavities have been developed to store very high-intensity beams with many short bunches. The design and performance of the cavities and other critical components, such as the input couplers and HOM dampers, are reported. The configuration of the RF systems is given and descriptions of various control loops are made, including a direct RF feedback loop and a 0-mode damping loop. The effects of transient beam loading due to a bunch gap on bunch phase modulations were simulated and measured. The development of a superconducting crab cavity, which is a component of luminosity upgrade strategy, is also presented.

KEKB accelerator control system

The KEKB accelerator control system including a control computer system, a timing distribution system, and a safety control system are described. KEKB accelerators were installed in the same tunnel where the TRISTAN accelerator was. There were some constraints due to the reused equipment. The control system is based on Experimental Physics and Industrial Control System (EPICS). In order to reduce the cost and labor for constructing the KEKB control system, as many CAMAC modules as possible are used again. The guiding principles of the KEKB control computer system are as follows: use EPICS as the controls environment, provide a two-language system for developing application programs, use VMEbus as frontend computers as a consequence of EPICS, use standard buses, such as CAMAC, GPIB, VXIbus, ARCNET, RS-232 as field buses and use ergonomic equipment for operators and scientists. On the software side, interpretive Python and SAD languages are used for coding application programs. The purpose of the radiation safety system is to protect personnel from radiation hazards. It consists of an access control system and a beam interlock system. The access control system protects people from strong radiation inside the accelerator tunnel due to an intense beam, by controlling access to the beamline area. On the other hand, the beam interlock system prevents people from radiation exposure by interlocking the beam operation. For the convenience of accelerator operation and access control, the region covered by the safety system is divided into three major access control areas: the KEKB area, the PF-AR area, and the beam-transport (BT) area. The KEKB control system required a new timing system to match a low longitudinal acceptance due to a low-alpha machine. This timing system is based on a frequency divider/multiply technique and a digital delay technique. The RF frequency of the KEKB rings and that of the injector Linac are locked with a common divisor frequency. The common divisor frequency determines the injection timing. The RF bucket selection system is also described. r 2002 Elsevier Science B.V. All rights reserved.

Status of Solenoid System to Suppress the Electron Cloud Effects at the KEKB

A large number of solenoids have been installed in the KEKB LER to remove the electron cloud. This paper describes recent solenoid winding work and the effect of it on electron cloud effects.

Asymmetric B-factory project at KEK

The present machine design of the future asymmetric B‐factory at KEK is reviewed. Beam energies and a design luminosity are chosen as 8×3.5 GeV2 and 1×1034/cm2/sec in due consideration of requirements from physics experiments. In the design, it is aimed to squeeze the vertical beta‐function at IP (β*y) to 1 cm. The beam‐beam limit is assumed to be 0.05 with the requirement that the bunch length should be half of β*y, i.e., 0.5 cm. Flat beams are chosen. In order to attain the design luminosity, beam currents of 2.6 A for the 3.5 GeV ring and 1.1 A for the 8 GeV ring are necessary. An all RF buckets filling scheme and a crab crossing scheme are adopted to realize the short bunches and to decrease RF voltages. The damped cavity is adopted to suppress the coupled bunch instability. Growth rates of the instability are estimated in the case that the damped cavities are used. Further extensive studies and R&D’s are necessary to realize the design luminosity.

Present status and beam-stability issues of the KEKB injector linac

The KEKB injector linac was completely upgraded for the KEK B-Factory (KEKB) project in March, 1998. Many difficulties have been overcome during the elaborate commissioning of the upgraded linac since the end of 1997. The 3.5-GeV positron and 8-GeV electron beams have been injected to the KEKB rings with good performance. Much effort has also been continuing to stabilize the intensity and quality of the beams. Some experimental results on the beam stability issues am shown together with the recent operation status in this report. A beam test on a new scheme of a two-bunch injection was started in order to increase the positron intensity since March, 2001.

Measurement of the polarization for the reactions K+n → K+n and K0p at 1.06, 1.28, 1.39 and 1.49 GeV/c

Abstract The polarization for the K+n elastic and charge-exchange reactions was measured at the momenta of 1.06, 1.28, 1.39 and 1.49 GeV/c. It was found to be negative for the K+n elastic process and generally positive for the charge-exchange process. The present results are compared with the predictions of phase shift analyses.

Recent Progress at KEKB

We summarize the machine operation of KEKB during past one year focusing on progress for this period.

The TELAS spectrometer

Abstract A magnetic spectrometer TELAS was constructed for experiments with a polarized target to measure various spin dependent variables. The system was first used for the measurement of polarization parameters on K + n elastic and charge exchange reaction and pn elastic scattering in the momentum range between 1 GeV/ c and 2 GeV/ c .

Commissioning of the Phase-I SuperKEKB B-Factory and Update on the Overall Status

The SuperKEKB B-Factory at KEK (Japan), after few years of shutdown for the construction and renovation, has finally come to the Phase-1 commissioning of the LER and HER rings, without the final focus system and the Belle II detector. Vacuum scrubbing, optics tuning and beam related background measurements were performed in this phase. Low emittance tuning techniques have also been applied in order to set up the rings for Phase-2 with colliding beams next year. An update of the final focus system construction, as well as the status of the injection system with the new positron damping ring and high current/low emittance electron gun is also presented.