Author: Ego, H.
Paper Title Page
MOOCB02 Commissioning and Performance of the Beam Monitor System for XFEL/SPring-8 “SACLA” 47
 
  • Y. Otake, C. Kondo, H. Maesaka
    RIKEN Spring-8 Harima, Hyogo, Japan
  • H. Ego, S. Matsubara, T. Matsumoto, T. Sakurai, H. Tomizawa, K. Yanagida
    JASRI/SPring-8, Hyogo-ken, Japan
  • S.I. Inoue
    SES, Hyogo-pref., Japan
 
  The construction of a beam monitor system for XFEL/SPring 8 “SACLA” was completed. The system was developed to realize a spatial resolution of less than 3 um to align a beam orbit for an undulator section with about 100 m long and a temporal resolution to measure bunch lengths from 1 ns to 30 fs to maintain a constant peak beam current conducting stable SASE lasing. The system principally comprises cavity type beam position monitors (BPM), current monitors (CT), screen monitors (SCM) and bunch length measurement instruments, such as an rf deflector and CSR detectors. Commissioning of SACLA started from March 2011, and the monitors performed sufficient roles to tune beams for the lasing. The achieved over-all performances of the system including DAQ are: the BPM have spatial resolution of 300 nm, the bunch length monitors observe bunch lengths from 1ns in an injector with velocity bunching to less than 30 fs after three-stage bunch compressors. The less than a 3 um spatial resolution of the SCM was also confirmed in practical beam operation. By these fulfilled performances, the stable lasing of SACLA will be achieved. This report describes commissioning, performance of the system.  
slides icon Slides MOOCB02 [7.516 MB]  
 
TUPC094 Development of High-speed Differential Current-transformer Monitor 1227
 
  • S. Matsubara, H. Ego, K. Yanagida
    JASRI/SPring-8, Hyogo-ken, Japan
  • A. Higashiya, S.I. Inoue, Y. Otake
    RIKEN/SPring-8, Hyogo, Japan
  • H. Maesaka
    RIKEN Spring-8 Harima, Hyogo, Japan
 
  The XFEL, which was named SACLA, was constructed in the SPring-8 site. In the SACLA, the bunch length of an electron beam is compressed from 1 ns to 30 fs, and the beam charge is decreased to obtain a genuine electron beam from 1nC to 0.3 nC for lasing. A new current-transformer (CT) monitor, which should measure the charge of the electron beam and make bunch length observation in velocity bunching process, was developed with two advantageous properties. One is differential output signal which suppresses common-mode noise from the thyratron of a klystron modulator by a factor of ten. Another property is high-speed signal output which provides a possibility to measure the bunch length and the time-of-flight (TOF) at the injector part of the SACLA. The output signal has 200 ps rise-time and a pulse width of 400 ps (FWHM) for an impulse beam. We successfully observed the bunch length between 1 ns and 400 ps around a 238 MHz buncher cavity. Moreover, we measured the TOF between two CTs with a few picoseconds resolution for a low-energy beam around 1 MeV. Thus, the new CT performance was confirmed to be sufficient for the SACLA.  
 
THPC032 Current Status of SPring-8 Upgrade Plan 2981
 
  • T. Watanabe, T. Asaka, H. Dewa, H. Ego, T. Fujita, K. Fukami, M. Masaki, C. Mitsuda, A. Mochihashi, T. Nakamura, H. Ohkuma, Y. Okayasu, Y. Shimosaki, K. Soutome, M. Takao
    JASRI/SPring-8, Hyogo-ken, Japan
  • T. Tanaka
    RIKEN Spring-8 Harima, Hyogo, Japan
 
  The SPring-8 upgrade plan has been discussed. The main goal is to replace the storage ring in the existing tunnel so that the resulting emittance will get as close to the diffraction limit in hard x-ray region as possible. For 10 keV photons, for instance, the diffraction limit corresponds to the emittance of as small as 10 pm.rad. For the challenging goal, the new ring features a multi-bend lattice with damping wigglers, which presumably enables us to reduce an emittance by two orders of magnitudes or more compared with the current double-bend lattice without damping wigglers. Up to now, a six-bend lattice has been mainly studied, which is supposed to generate a natural emittance of 60–70 pm.rad for 6 GeV. In addition, damping wigglers and coupling control should assist to reduce the emittance even more for approaching the ultimate goal. The major modification requires not only an advanced lattice design via manipulation of non-linear beam dynamics but also extensive technological developments in almost every component such as magnets, monitors, and RF systems. The overall review of the upgrade plan, including some detailed discussions on the critical issues, will be presented.  
 
THPC088 Performance of RF System for XFEL/SPring-8 Injector 3101
 
  • T. Asaka
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • T. Asaka, H. Ego, H. Hanaki, T. Kobayashi, S. Suzuki, T. Taniuchi
    JASRI/SPring-8, Hyogo-ken, Japan
  • T. Inagaki
    RIKEN/SPring-8, Hyogo, Japan
  • Y. Otake, T. Shintake, K. Togawa
    RIKEN Spring-8 Harima, Hyogo, Japan
 
  In the XFEL/SPring-8 accelerator, the RF processing of an injector for the 8-GeV accelerator were carried out during two months after the installation of all the main components of the accelerator was completed in January 2011. To realize stable bunch compression process without the emittance growth, the injector adopts the combination of an extremely low emittance thermionic gun and multi-stage RF cavities for velocity bunching. In addition, in order to reduce the emittance growth occurring at the transition from the velocity bunching to acceleration, the newly developed L-band APS type accelerating structures and a waveguide system were introduced in the injector. Since an intensity of beam current is affected by the slight variations of RF power and phase of these RF equipment, we have carried out thorough countermeasures to complete highly-stabilized RF systems. Consequently, the stability of RF power and phase in rated operating condition of each RF cavity achieved 20 ppm (std.) and 0.06˚ (std.), respectively. In this paper, we describe the stability performances and RF processing of these RF systems in the injector.  
 
TUPC092 Transverse C-band Deflecting Structure for Longitudinal Phase Space Diagnostics in the XFEL/SPring-8 “SACLA” 1221
 
  • H. Ego
    RIKEN/SPring-8, Hyogo, Japan
  • T. Hashirano, S. Miura
    MHI, Hiroshima, Japan
  • H. Maesaka, Y. Otake
    RIKEN Spring-8 Harima, Hyogo, Japan
  • T. Sakurai
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
 
  In SPring-8, the 8 GeV compact XFEL “SACLA” is under commissioning. A single bunch of electrons is compressed down to about 30 fs for brilliant SASE X-ray lasing. It is an important key of stable lasing to investigate the longitudinal phase space and the sliced emittance of a lasing part of the bunch by using a transverse RF deflector. We developed a high gradient C-band deflecting structure operated at 5712 MHz for the bunch diagnosis with a resolution of femtosecond regime at a limited space in the SACLA. The backward travelling-wave of the HEM11-5pi/6 mode is excited in the cylindrical structure periodically loaded with racetrack-shaped irises. The featuring irises suppress rotation of the deflection plane and generate strong cell-to-cell coupling for stable resonance. Two 1.8m-long structures were fabricated and installed in the SACLA. They successfully generated a deflection voltage over 40 MV and pitched the bunch at the zero-crossing RF phase. In this paper, we present the details of the fabrication and the deflecting performance of the structures applied to the diagnosis.