Author: Inoue, S.I.
Paper Title Page
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.  
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.  
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]