Keyword: feedback
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MOPO106 New Digital LLRF System for HIT controls, cavity, LLRF, linac 227
 
  • E. Feldmeier, Th. Haberer, A. Peters
    HIT, Heidelberg, Germany
 
  The Heidelberg Ion Therapy Center HIT is in clinical operation since 2009. The accelerator complex consists of a linear accelerator and a synchrotron to provide carbon ions and protons for clinical use as well as helium and oxygen ions. The analog LLRF system for the linac should be replaced after more than 10 years of continuous operation. In its life-time the LLRF caused no interruption of the clinical operation with a downtime of more than 15 minutes. In order to keep the reliability in the next 10 years at least as high, a new digital LLRF system is planned. Further difficulties for the installation of a new system are due to the clinical full time usage of the accelerator and the short maintenance slots of only two days in series.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO106  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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MOPO107 Performance Evaluation of the RF Reference Phase Stabilization System on Fiber-optical Link for KEK e/e+ Injector LINAC linac, controls, EPICS, network 230
 
  • N. Liu, B. Du
    Sokendai - Hayama, Hayama, Japan
  • D.A. Arakawa, H. Katagiri, T. Matsumoto, S. Michizono, T. Miura, F. Qiu, Y. Yano
    KEK, Ibaraki, Japan
  • T. Matsumoto, T. Miura, F. Qiu
    Sokendai, Ibaraki, Japan
 
  KEK e/e+ injector is the 600 m J-shaped LINAC which has 8 RF sectors. Stabilization of RF phase reference for long distance transmission is necessary for stable RF operation. In the present system, single-mode fiber-optical links without feedback control are used from sector 2 to 5. For the SuperKEKB, the phase stability requirement is within 0.1 deg. rms. The more stable RF phase reference is necessary to improve the phase stability. In this paper, a feedback control system for RF reference phase stabilization is tested for system performance evaluation. The temperature and humidity characteristics of the electric and optical components and phase stabilized optical fiber (PSOF) with different wavelengths will also be presented.  
poster icon Poster MOPO107 [2.026 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO107  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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MOPO111 Development of New LLRF System at the J-PARC Linac LLRF, linac, FPGA, low-level-rf 233
 
  • K. Futatsukawa, Z. Fang, Y. Fukui
    KEK, Ibaraki, Japan
  • Y. Sato
    Nippon Advanced Technology Co., Ltd., Tokai, Japan
  • S. Shinozaki
    JAEA/J-PARC, Tokai-mura, Japan
 
  In the J-PARC linac, the LLRF system with the digital feedback (DFB) and the digital feedforward (DFF) was adopted for satisfying requirement of amplitude and phase stabilities. It has been operated without serious problems. However, it has been used since the beginning of the J-PARC and more than ten years have already passed since the development. The increase of the failure frequency for this system is expected. Additionally, it is difficult to maintain it for some discontinued boards of DFB and DFF and the older developing environment of software. Therefore, we are starting to study the new LLRF system of the next generation. In the present, we are exploring several possibilities of a new way and investigating each advantage and disadvantage. The project and the status of the development for the new system in the J-PARC linac LLRF are introduced.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO111  
About • paper received ※ 22 September 2018      issue date ※ 18 January 2019  
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TUPO029 Highlights of the XM-3 Cryomodule Tests at DESY cavity, cryomodule, FEL, operation 388
 
  • J. Branlard, V. Ayvazyan, A. Bellandi, J. Eschke, C. Gumus, D. Kostin, K.P. Przygoda, H. Schlarb, J.K. Sekutowicz
    DESY, Hamburg, Germany
  • W. Cichalewski
    TUL-DMCS, Łódź, Poland
 
  To investigate the feasibility of the continuous wave (cw) upgrade of the European XFEL (E-XFEL) DESY, on-going tests are performed on E-XFEL prototype and production cryomodules since 2011. For these studies, DESY’s Cryo-Module Test Bench (CMTB) has been equipped with a 105 kW cw operating IOT in addition to the 10MW pulsed klystron, making CMTB a very flexible test stand, enabling both cw and pulse operation. For these tests, E-XFEL-like LLRF electronics is used to stabilize amplitude and phase of the voltage Vector Sum (VS) of all 8 cavities of the cryomodule under test. The cryomodule most often tested is the pre-series XM-3, unique since it is housing one fine grain niobium and seven large grain niobium cavities. In autumn 2017, additional spacers were installed on all 8 input couplers to increase the maximum reachable loaded quality factor Ql beyond 2·107. With higher Ql, up to 6·107 for 6 cavities and 2.7·107 for 2 cavities, we have investigated the VS stability and SRF-performance of this cryomodule under various conditions of cooling down rate and operation temperature 1.65K, 1.8K and 2K, at gradients up to ca. 18MV/m. The results of these tests are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO029  
About • paper received ※ 11 September 2018      issue date ※ 18 January 2019  
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TUPO132 Implementation of the Beam Loading Compensation Algorithm in the LLRF System of the European XFEL LLRF, controls, cavity, FEL 594
 
  • Ł. Butkowski, J. Branlard, M. Omet, R. Rybaniec, H. Schlarb, Ch. Schmidt
    DESY, Hamburg, Germany
 
  In the European XFEL, a maximum number of 2700 electron bunches per RF pulse with beam currents up to 4.5mA can be accelerated. Such large beam currents can cause a significant drop of the accelerating gradients, which results in large energy changes across the macro-pulse. But, the electron bunch energies should not deviate from the nominal energy to guarantee stable and reproducible generation of photon pulses for the European XFEL users. To overcome this issue, the Low Level RF system (LLRF) compensates in real-time the beam perturbation using a Beam Loading Compensation algorithm (BLC) minimizing the transient gradient variations. The algorithm takes the charge information obtained from beam diagnostic systems e.g. Beam Position Monitors (BPM) and information from the timing system. The BLC is a part of the LLRF controller implemented in the FPGA. The article presents the implementation of the algorithm in the FPGA and shows the results achieved with the BLC in the European XFEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO132  
About • paper received ※ 11 September 2018      issue date ※ 18 January 2019  
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