Keyword: cavity
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MOPGF026 Laser Beam Profiling and Further Improvements to the FHI FEL FEL, laser, electron, detector 1
  • H. Junkes, W. Schöllkopf, M. Wesemann
    FHI, Berlin, Germany
  A mid-infrared FEL has been established at the Fritz-Haber-Institut in Berlin. It is used for spectroscopic investigations of molecules, clusters, nanoparticles and surfaces. The oscillator FEL is operated with 15 - 50 MeV electrons from a normal-conducting S-band linac equipped with a gridded thermionic gun and a chicane for controlled bunch compression. The EPICS software framework was choosen to build the control system for this facility. In an effort to support the various experimenters two different Laser Beam Profiling cameras have been integrated. Here, the areadetector framework with genicam integration is used. The control system was also expanded with fast digitizers (SIS3316) but connected via Ethernet instead of using a VMEbus crate controller to get a higher flexibility. A iPad app for monitoring completes the enhancement. This paper presents design and implementation aspects of the upgrade, its capabilities, and lessons learned during the development.  
poster icon Poster MOPGF026 [15.827 MB]  
MOPGF079 European XFEL Cavities Piezoelectric Tuners Control Range Optimization operation, controls, LLRF, linac 1
  • W. Cichalewski, A. Napieralski
    TUL-DMCS, Łódź, Poland
  • J. Branlard, Ch. Schmidt
    DESY, Hamburg, Germany
  The piezo based control of the superconducting cavity tuning has been under the development over last years. Automated compensation of Lorentz force detuning of FLASH and European X-FEL resonators allowed to maintain cavities in resonance operation even for high acceleration gradients (in range of 30 MV/m). It should be emphasized that cavity resonance control consists of two independent subsystems. First of all the slow motor tuner based system can be used for slow, wide range mechanical tuning (range of hundreds of kHz). Additionally the piezo tuning system allows for fine, dynamic compensation in a range of ~1 kHz. In mentioned pulse mode experiments (like FLASH), the piezo regulation budget should be preserved for in-pulse detuning control. In order to maintain optimal cavity frequency adjustment capabilities slow motor tuners should automatically act on the static detuning component at the same time. This paper presents work concerning development, implementation and evaluation of automatic superconducting cavity frequency control towards piezo range optimization. FLASH and X-FEL dedicated cavities tuning control experiences are also summarized.  
poster icon Poster MOPGF079 [0.932 MB]  
MOPGF093 Real-time Beam Loading Compensation for Single SRF Cavity LLRF Regulation LLRF, real-time, detector, electron 1
  • I. Rutkowski, M. Grzegrzólka
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  • Ł. Butkowski, Ch. Schmidt
    DESY, Hamburg, Germany
  • M. Kuntzsch
    HZDR, Dresden, Germany
  Stable and reproducible generation of a photon beam at Free Electron Lasers (FELs) necessitates a low energy spread of the electron beam. A low level radio frequency (LLRF) control system stabilizes the RF field inside accelerating modules. An electron beam passing through the cavity induces a drop in the actual stored field proportional to the charge, the cavity shunt impedance, and the bunch repetition rate. The feedback loop compensates for the perturbation after the accelerating gradient drops. Due to the digital loop delay and limited bandwidth of the closed loop system, this disturbance induces control errors which can increase beam energy spread. An open-loop controller uses information obtained from the beam diagnostic systems accounting in real-time for fluctuations of the beam current. This paper describes the bunch charge detection scheme, its implementation, as well as results of the tests performed on the ELBE (Electron Linac for beams with high Brilliance and low Emittance) radiation source at the HZDR (Helmholtz-Zentrum Dresden-Rossendorf) facility.  
poster icon Poster MOPGF093 [4.046 MB]  
WEPGF014 A Data Acquisition System for Abnormal RF Waveform at SACLA GUI, LLRF, controls, data-acquisition 1
  • M. Ishii, M. Kago
    JASRI/SPring-8, Hyogo-ken, Japan
  • T. Fukui
    RIKEN SPring-8 Center, Innovative Light Sources Division, Hyogo, Japan
  • T. Hasegawa, M. Yoshioka
    SES, Hyogo-pref., Japan
  • T. Inagaki, H. Maesaka, T. Ohshima, Y. Otake
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • T. Maruyama
    RIKEN/SPring-8, Hyogo, Japan
  At the X-ray Free Electron Laser (XFEL) facility, SACLA, an event-synchronized data acquisition system has been utilized for the XFEL operation. This system collects every shot-by-shot data, such as point data of the phase and amplitude of the RF cavity pickup signals, in synchronization with the beam operation cycle. This system also acquires RF waveform data every 10 minutes. In addition to the periodic waveform acquisition, an abnormal RF waveform that suddenly occurs should be collected for failure diagnostics. Therefore, we developed an abnormal RF waveform data acquisition (DAQ) system, which consists of the VME systems, a cache server, and a NoSQL database system, Apache Cassandra. When the VME system detects an abnormal RF waveform, it collects all related waveforms of the same shot. The waveforms are stored in Cassandra through the cache server. Before the installation to SACLA, we ensured the performance with a prototype system. In 2014, we installed the DAQ system into the injection part with five VME systems. In 2015, we will acquire waveforms from the low-level RF control system configured by 74 VME systems at the SACLA accelerator.  
poster icon Poster WEPGF014 [0.974 MB]  
WEPGF119 Bunch to Bucket Transfer System for FAIR synchrotron, target, kicker, timing 1
  • J.N. Bai
    IAP, Frankfurt am Main, Germany
  • R. Bär, D. Beck, O.K. Kester, D. Ondreka, C. Prados, W.W. Terpstra
    GSI, Darmstadt, Germany
  • T. Ferrand
    TEMF, TU Darmstadt, Darmstadt, Germany
  For the FAIR accelerator complex, synchronization of the bunch to bucket (B2B) transfer will be realized by the General Machine Timing system and the Low-Level RF system. Based on these two systems, both synchronization methods, the phase shift and the frequency beating method, are available for the B2B transfer system for FAIR. This system is capable to realize the B2B transfer within 10ms and the precision better than 1 degree for ions over the whole range of stable isotopes. At first, this system will be used for the transfer from the SIS18 to the SIS100. It will then be extended to all transfers at the FAIR accelerator facility. This paper introduces the synchronization methods and concentrates on the standard procedures and the functional blocks of the B2B transfer system.  
poster icon Poster WEPGF119 [1.489 MB]