Author: Otake, Y.
Paper Title Page
MOPC018 Operation Status of C-band High Gradient Accelerator for XFEL/SPring-8 (SACLA) 104
 
  • T. Inagaki, C. Kondo, T. Ohshima, Y. Otake, T. Sakurai, K. Shirasawa
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • T. Shintake
    RIKEN Spring-8 Harima, Hyogo, Japan
 
  XFEL project in SPring-8 have constructed a compact XFEL facility*. In order to shorten an accelerator length, a C-band (5712 MHz) accelerator was employed due to a higher accelerating gradient than that of an S-band accelerator. Since a C-band accelerating structure generates a gradient of higher than 35 MV/m, the total length of an 8 GeV accelerator fits within 400 m, including 64 C-band RF units, 4 S-band RF units, an injector and three bunch compressors. The accelerator components were carefully installed by September 2010. Then we have performed high power RF conditioning. After 500 hours of the conditioning, the accelerating gradient of each C-band structure was reached up to 35 MV/m without any particular problem. The RF breakdown rate is low enough for an accelerator operation. Since February 2011, we started the beam commissioning for XFEL. The C-band accelerator has accelerated the electron beam up to 8 GeV, with an accelerating gradient of 33-35 MV/m in average. The energy and the trajectory of the electron beam was stable, thanks to the stabilization of a klystron voltage of 350 kV within 0.01% by a high precision high voltage charger.
*The facility was recently named SACLA (SPring-8 Angstrom Compact free electron LAser).
 
 
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]  
 
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.  
 
TUPC093 CSR Bunch Length Monitor for XFEL/SPring-8 - SACLA 1224
 
  • C. Kondo, S. Matsubara, T. Matsumoto
    JASRI/SPring-8, Hyogo-ken, Japan
  • S.I. Inoue, H. Maesaka, Y. Otake
    RIKEN Spring-8 Harima, Hyogo, Japan
 
  SPring-8 Angstrom Compact Free Electron Laser (SACLA) is now under commissioning operation, aimed at the generation of a sub-angstrom free electron laser (FEL). In order to ensure the stable FEL generation, non-distractive bunch length monitors utilizing coherent synchrotron radiation (CSR) are installed. The monitors are located at the downstream of individual bunch compressor (BC1-BC3), and they measure the radiation emitted at the individual last magnets of the chicanes. At the magnets, beams with bunch lengths form 10 fs to 1000 fs generate the CSRs with a spectrum ranging the almost whole infrared region (0.03 - 3 THz). The CSRs are detected by a Schottky diode at the BC1, or pyroelectric detectors and a simple organic lens optical system at BC2 and 3. The bunch length monitor systems are used for bunch length feedback control to obtain the stable lasing by changing the rf parameter of acceleration cavities before the BCs. A preliminary system for the above mentioned system was tested at the SCSS test accelerator, and it showed sufficient performance to measure bunch length up to 300 fs. In this report, we describe the design and the results of the first operation.  
 
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.  
 
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.  
 
WEPC143 First Operation of the SACLA Control System in SPring-8 2325
 
  • R. Tanaka, Y. Furukawa, T. Hirono, M. Ishii, M. Kago, A. Kiyomichi, T. Masuda, T. Matsumoto, T. Matsushita, T. Ohata, C. Saji, T. Sugimoto, M. Yamaga, A. Yamashita
    JASRI/SPring-8, Hyogo-ken, Japan
  • T. Fukui, T. Hatsui, N. Hosoda, T. Ohshima, T. Otake, Y. Otake, H. Takebe
    RIKEN/SPring-8, Hyogo, Japan
  • H. Maesaka
    RIKEN Spring-8 Harima, Hyogo, Japan
 
  The control system design of the X-ray free electron laser facility (SACLA) in SPring-8 has started in 2006. Now, the facility has completed to start beam commissioning in February 2011. The electron beams were successfully accelerated up to 8 GeV and the first SASE X-ray was observed. The control system adopts the 3-tier standard model by using MADOCA framework developed in SPring-8. The upper control layer consists of Linux PCs for operator consoles, Sybase RDBMS for data logging and FC-based NAS for NFS. The lower layer consists of VMEbus systems with off-the-shelf I/O boards and specially developed boards for RF waveform processing with high precision. Solaris OS is adopted to operate VMEbus CPU. The PLC is used for slow control and connected to the VME systems via FL-net. The Device-net is adopted for frontend device control to reduce the number of signal cables. Some of VMEbus systems have a beam-synchronized data-taking system to meet 60Hz electron beam operation for the beam tuning diagnostics. The accelerator control system has gateways not only to monitor device status but also control the tuning points of the facility utility system, especially cooling water.