BEAM DECOHERENCE DUE TO COMBINATION OF WAKE FORCE AND NONLINEARITY IN SP-RING-8 STORAGE RING

Abstract To understand particle behavior from a beam injection state to equilibrium state determined by radiation effects, we have performed a simple experiment to observe the beam decoherence, i.e., temporal variation of the damping of beam coherent motion generated by a single horizontal kicker. We found that the beam decoherence much depends on chromaticities, the sign of amplitudedependent tune shift and beam current. This suggests that short-range wake force and nonlinearity of ring parameters play important roles in the observed phenomena. Simulations with transverse wake fields show good agreements with the measurements

MAGNETIC-FIELD VARIABLE PERMANENT DIPOLE MAGNET FOR FUTURE LIGHT SOURCES

Abstract A permanent dipole magnet with variable magnetic field has been designed, fabricated, and tested at SPring-8. Permanent magnet can be advantageous over electromagnet in terms of power consumption, stability and reliability etc. One of critical issues to apply permanent magnets to future light sources and other accelerators is that the magnetic field should be somehow tuned. In designing future light sources, combined-function or longitudinal gradient magnet may play a key role in achieving extremely small emittance. Therefore, it may not be appropriate to change a gap for changing the field. We have proposed an alternative way to tune the magnetic field of permanent magnet by using outer plates, and the performance has been investigated

POSITION OBSERVATION FOR MAGNET UNIT AT SPRING-8

Abstract The position observations for the magnet unit of the SPring-8 storage ring are executed using the laser tracker for horizontal plane and the precision level N3 or DiNi11 for vertical plane. And, the measurements are carried on each year during the summer maintenance periods to monitor the changes. This paper will give a brief description of the survey methods as well as the results of measurements

NUMERICAL CALCULATION AND EXPERIMENT OF ION RELATED PHENOMENON IN SPring-8 STORAGE RING

Abstract In the SPring-8 storage ring, we have tried to develop new filling patterns which have equally spaced bunches. In the development, we have found vertical beam instability which strongly depends on the bunch interval; the instability becomes stronger when the bunch interval becomes shorter. From the dependence of the filling pattern, we have speculated that the instability is ion related phenomenon, and performed computer simulation which is based on macroparticle calculation. The agreement between the change in the observed vertical beam size on the bunch interval and the result of the simulation is good

DIAMOND-BASED BEAM HALO MONITOR EQUIPPED WITH RF FINGERS FOR SACLA*

Abstract The diamond-based bea

X-ray imaging microscope with a partial coherent illumination

ABSTRACT An x-ray imaging microscopy experiment n a s performed at the x-ray energ!-of 8 keV. A Fresnel zone plate (FZP) fabricated by electron-beam lithography technique was used as an objective. Material of the zone structure is tantalum. The experiment was done at the undulator beamline BL47XU of Spring-8. Undulator radiation u-as monochromatized by passing through a liquid nitrogen cooled Si 11 1 double crystal monochromator. In order to eliminate speckle-like background noise; a partial coherent illumination was introduced by using a -'beam diffuser" consisted of graphite powder. Beam spread of the illumination with the diffuser was about 35 p a d . A charge coupled device (CCD) camera coupled d h a phosphor screen and a microscope objective (x 12 or x 24) was used as an image detector. Converted pixel size with the x 24 lens was 0.5 pm. Magnitication of the x-ray microscope system was set to be 7.61 -13. Pitch of0.6 pm (0.3 pm line and 0.3 pm space) pattern of the test chart \\.as resolvedd; and the outermost zone structure of the same type of FZP was obsemed. Imaging properties are also discussed by using Hopkins' optical imaging t h e o~

RE-ENGINEERING OF THE SPRING-8 RADIATION MONITOR DATA ACQUISITION SYSTEM

Abstract We have re-engineered the data acquisition system for SPring-8 radiation monitors. The previous system consisted of dedicated digital indicator/controller modules (DICMs) optically linked with radiation monitors, embedded PCs for data acquisition, and programmable logic controllers (PLCs) for 1-h integrated dose surveillance. The embedded PCs periodically collected radiation data from the DICMs through GPIB. The DICMs and the dose surveillance PLCs were interfaced with an accelerator radiation safety interlock system (ARSIS). These components were dedicated, blackboxed, and complicated for operations. The GPIB interface was legacy and not reliable enough for the critical system. Therefore, we re-engineered the previous system by adopting PLCs and FL-net. Local PLCs were deployed as substitutes for all the previous embedded PCbased components. Another PLC was installed to enable centralized management of all 81 monitors. All the new PLCs and a VME computer for data acquisition were connected via FL-net networks. In this paper, the new system and a method for upgrading this system within the short shutdown interval of the accelerator operations are described

INTEGRATION OF COMPUTERS AND TERMINALS BY INTRODUCTION OF THE VIRTUALIZATION TECHNOLOGY AND THIN CLIENT IN SPRING-8

Abstract We applied virtualization technology to server computers to form a high-availability redundant server system. At the same time, we replaced general-purpose PCs with thin-client terminals. The introduction of these technologies reduced the number of computers substantially and gave us an opportunity to develop highavailability computing systems with inexpensive management. To ensure high availability, the server computer has to be built using reliable components with redundant architecture instead of reducing the number of computers. The application-processing performance of the client OS on the host OS was greater than or equal to that a standalone server. The combination of the recent multicore architecture server and Xen hypervisor showed good performance as a result of appropriately allocating system resources to Xen Hypervisor. The thin-client system is useful for integrating widely scattered terminals into a small number of systems, which will reduce maintenance effort. The integrated virtual machine system and thin-client system use a network-attached storage system that runs under the redundant configuration

OBSERVATION OF COHERENT SYNCHROTRON RADIATION FROM THREE TYPES OF BEAM AT NEWSUBARU

Abstract Coherent synchrotron radiation from three types of the beam was observed at NewSUBARU storage ring. One was the radiation burst from the high current beam, higher than 1.0 nC/bunch. The second was the steady state radiation from a low current but very short bunched beam. The third was the radiation pulse from the linac beam in the storage ring at just after the injection

OPERATION STATUS OF C-BAND HIGH-GRADIENT ACCELERATOR FOR XFEL/SPRING-8 (SACLA)

Abstract To fit our XFEL machine of SACLA (SPring-8 Angstrom Compact Free Electron Laser) in the small campus of SPring-8, a C-band (5712 MHz) high-gradient accelerator with a designed acceleration gradient of 35 MV/m is indispensable. Highly-stable acceleration for an energy chirp in bunch compression process is required for stable lasing. The low-trip rate and the low-dark current of C-band accelerating structures are also crucial for stable accelerator operation. After 1000 hours of the RF conditioning, the C-band accelerator has daily accelerated electron beams up to 7.0-7.4 GeV, with the designed accelerator gradient of about 35 MV/m. The trip rate of the whole accelerator is once per 30 minutes, which is an acceptable rate for beam commissioning. The energy stability of the electron beam was 0.014% (STD), owing to the stabilization of a PFN charging voltage with a 10 ppm (STD) accuracy by a high-precision high-voltage charger. The amount of dark current was several pC/pulse, which was small enough for operation