Norihiko Kamikubota

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.

Present Status of the J-PARC Control System

The present status of the design and construction of the control system for Japan Proton Accelerator Research Complex (J-PARC) is given. J-PARC is a 3-stage accelerator complex with a 200MeV Linac, a 3GeV Rapid Cycling Synchrotron (RCS) and a 50GeV Main Ring synchrotron (MR). The accelerators are under construction jointly by Japan Atomic Energy Research Institute (JAERI) and KEK, High Energy Accelerator Research Organization. Linac and RCS are being constructed mainly by JAERI and MR is mainly by KEK. [1,2] And the control systems for Linac and RCS [17] are constructed mainly by JAERI and that of MR is done mainly by KEK. [3] Commissioning of Linac, RCS and MR are scheduled in September 2006, May 2007, and January 2008, respectively. There are three control systems under construction corresponding to three accelerators. These three control systems will be operated from one central control room when each control system is completed construction. We chose Experimental Physics and Industrial System (EPICS) [4] as the software environment so that three control systems can be unified easily to single control system. J-PARC control system has the three-layer standard model architecture for accelerator controls that is very common in the EPICS world. We have chosen the standard network protocol TCP/IP and UDP/IP as the J-PARC standard field-bus used to connect interface units that links accelerator component to the control system.

New control system with VME and workstations for the KEK e−/e+ linac

Abstract A new control system has been introduced for the KEK electron/positron linac which comprises seven VME stations with the OS-9 operating system and UNIX-based workstations. All of the VME stations and workstations communicate with each other, using the TCP/IP protocol through an Ethernet connection. New control software has been developed with attention being paid to a smooth transition from the old control system. The new software provides transparent functions for controlling the basic accelerator components. The new system started operation in October, 1993.

New pre-injector of the KEK 2.5-GeV linac and its performance

The injection system (pre-injector) of the KEK 2.5-GeV linac has been upgraded so that we can investigate intense beam acceleration for the KEK B-factory project. It requires intense beams to achieve a short injection time in practice. An outline of the new pre-injector and its performance is given.<<ETX>>

Increase of positrons by a high-intensity two-bunch acceleration scheme at the KEKB linac

As the accumulation current of positrons increases in the KEKB ring, the injection time is becoming longer. It will thus be one of the most important issues affecting the accumulation of the integrated luminosity. As one of the steps, we introduced a high-intensity two-bunch acceleration scheme at the KEKB linac to intensify positrons by means of doubling the primary electrons. We recently obtained test results of 0.54 nC for the first bunch and 0.49 nC for the second bunch at the linac end. This scheme increased the positron intensity by nearly 65%. Since the linac frequency is not a harmonic number of the LER frequency, the best time interval between two bunches is 96.29 ns, corresponding to 49 LER-buckets. Even with this limitation, it is undoubtedly a very useful scheme for increasing the positron injection rate. The beam test results are described.

Beam test of radiation hardness of a scintillating tile/fiber calorimeter

Abstract Radiation hardness of a scintillating tile/fiber calorimeter is studied by irradiating electromagnetic test modules with 2.5 GeV electrons at the KEK linac. The induced damage is evaluated in a 2 GeV electron test beam by measuring the reduction in pulse height after irradiation. The pulse height peak for 2 GeV electrons is found to decrease by 19.3 ± 1.3% for a dose of 0.61 Mrad and 14.9 ± 2.7% for 0.33 Mrad. In addition to these modules, several tile/fiber assemblies were irradiated up to 4.8 Mrad and the damage as a function of dose was measured with a radioactive source. Effects of radiation damage on the linearity and energy resolution at higher energies are evaluated using a GEANT simulation and the measured damage.

An operator-console system of the photon factory injector linac

Abstract It is sometimes difficult to unify accelerator control systems constructed in different ways. This problem arose in unifying the control systems of the injector linac and the storage ring making up the Photon Factory of the National Laboratory for High Energy Physics. One easy approach is to unify only the operator consoles; the unified console is connected to both separate control systems using gateways. The operator-console system of the Photon Factory injector linac has been designed and constructed using this approach. It consists of several workstations interconnected via a local-area network, a gateway to the old linac control network and a CATV system for the real-time display of the accelerator status. In this way the linac will be controlled from the control center of the Photon Factory storage ring.

Tool for Device Histories at the KEK Linac

Almost all of the signals of the linac control devices, roughly 6000 bytes in total, are scanned with a one-second interval. The changes are recorded into log files during the linac operation as long as three months. A tool, called ’dev hist’, has been developed in order to display the histories of specified devices from these log files. This tool provides mouse-oriented controls to select a device and a time-window of interest.

Recent progress in the control system of the KEK 2.5 GeV e−/e+ linac

Abstract The KEK 2.5 GeV linac is controlled by a distributed processor network having minicomputers and microcomputers interconnected with fiber-optic networks. This system has operated for seven years; however, the system capability has become inadequate for the increasing demands. Thus a new network system, using the TCP/IP protocol suite over Ethernet, has been introduced. New control software to enable more reliable operation of the linac is now under development.

Residual Field Correction of Pulsed Bending Magnet

At the J-PARC, to deliver bunches of protons to both of beam transport lines, 3NBT and 3-50BT, a pulsed bending magnet (PB) [1] is operated. Bunches between K1 and K4 timing are bended to 3-50BT, and the other bunches through the PB to 3NBT after the magnetic field is fallen down. The rise and fall time of the pulsed bending magnet was designed as less than 40msec because the interval time of bunches is 40msec. However the residual magnetic field after K4 has been observed as equal to 0.27mrad kick angle at K5 as shown in Fig1. Therefore, bunches at K5, K6 and K7 have not been filled to avoid time depended beam orbit shift at the target of Material and Life Science Experimental Facility (MLF). If the residual field of PB is corrected, the production beam power for the MLF will be higher with K5, K6 and K7 bunches. To reduce the PB residual field, additional coils have been wound to poles of the PB, and a power supply has been installed. Results of the beam study by using the additional correction coil will be reported in this paper.