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Simrock, S.

Paper Title Page
MOPAN018 Performance of the New Coupled Bunch Feedback System at HERA-p 185
  • M. G. Hoffmann, S. Choroba, F. Eints, U. Hurdelbrink, P. Morozov, Y. Nechaev, J. Randhahn, S. Ruzin, S. Simrock, V. Soloviev
    DESY, Hamburg
  A longitudinal broadband damper system to control coupled bunch instabilities (LMBF) has been installed in the 920~GeV proton accelereator HERA-p at the Deutsches Elektronen-Synchrotron DESY in Q4/2005. The Feedback system was fully automated, in order to relieve the operator from manual control during system operation. During comissioning in Q1/2006 it turned out that the performance goals were reached and the noise is not as much a problem as expected. The proton bunch length is significantly reduced as is the stretching of the bunches over runtime. Without additional damping the bunch length is about 1.5~ns (FWHM) at the beginning of a typical luminosity run. With the new feedback system in operation the bunch length could be decreased to 1.0 ns at best. Although the bunches get longer during the luminosity run, the integrated luminosity gain is thus up to 5%. System optimization points were found in automatic gain adjustment during acceleration ramp, oscillation level triggering and timing of kicker pulse to bunch. We describe the commissioning of the multibunch feedback system and the adjustment procedures. A performace overview after one year of operation is given.  
MOPAN019 Performance of the New Master Oscillator and Phase Reference System at FLASH 188
  • S. Simrock, M. Felber, M. Hoffmann, B. Lorbeer, F. Ludwig, H. C. Weddig
    DESY, Hamburg
  • K. C. Czuba
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw
  The master oscillator and phase reference system at FLASH must provide several rf reference frequencies to widely spread locations with low phase noise and small long term phase drifts. The phase noise requirements of the 1300 MHz reference is of the order of 0.1 deg. while short and medium term phase stability is of of the order of 0.1 deg. and 1 deg. respectively. The frequency distribution system employs a temperature stabilized coaxial line for rf power distribution and a fiber optic system for the monitoring of phase drifts. Presented are the the concept, design and performance measured in the accelerator environment.  
WEPMN010 Linearization of Downconversion for IQ Detection Purposes 2068
  • M. K. Grecki, W. Koprek, S. Simrock
    DESY, Hamburg
  Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 ''Structuring the European Research Area'' program (CARE, contract number RII3-CT-2003-506395).

Measurements of effective Radio Frequency (RF) field parameters (amplitude and phase) are tasks of great importance in high-energy accelerators*. The RF signal is downconverted in frequency to intermediate frequency (IF) but keeping the information about amplitude and phase. The IF signal is then sampled in ADC and processed in digital IQ detector computing the I and Q components**. The downconverter is a nonlinear device thus not only the fundamental frequency but also its harmonics are present and sampled by ADC. For a typical downconverter (used in FLASH LLRF system) the higher order harmonics levels depend on RF signal level and are about 40dBm lower than the fundamental frequency component. These harmonics can produce errors in IQ detector of up to few percent in amplitude and few degree in phase. These errors depends not only on nonlinearity of downconverter but also on the IQ detection scheme*** (IF and sampling rate SR). The paper presents the optimization of the IQ detection scheme (choosing the IF and SR) taking into account the nonlinear characteristics of the downconverter.

*Grelick A. et all:A High-Resolution…, Proc. LINAC 2004,715-718**Grecki M. et all:Estimation of IQ…, Proc. MIXDES 2005,783-788***Simrock S. et all:Considerations…, Proc. EPAC 2006,1462-1464

WEPMN011 Multichannel Downconverter for the Next Generation RF Field Control for VUV- and X-Ray Free Electron Lasers 2071
  • M. Hoffmann, F. Ludwig, H. Schlarb, S. Simrock
    DESY, Hamburg
  Funding: We acknowledge financial support by DESY Hamburg and the EUROFEL project.

For pump- and probe experiments at VUV- and X-ray free-electron lasers the stability of the electron beam and timing reference must be guaranteed in phase for the injector and bunch compression section within a resolution of 0.01 degree (rms) and in amplitude within 1 10-4 (rms). The performance of the field detection and regulation of the acceleration RF critically influences the phase and amplitude stability. For the RF field control, a multichannel RF downconverter is used to detect the field vectors and control the vectorsum of 32 cavities. In this paper a new design of an 8 channel downconverter is presented. The downconverter frontend consists of a passive rf double balanced mixer input stage, intermediate filters and an integrated 16bit analog-to-digital converter (ADC). The design includes a digital motherboard for data preprocessing and communication with the controller. In addition we characterize the downconverter performance in amplitude and phase jitter, temperature drifts and channel crosstalk in laboratory environment as well as for accelerator operation.

WEPMN052 FPGA - based Control System for Piezoelectric Stacks used for SC Cavity's Fast Tuner 2155
  • P. M.S. Sekalski, J. W. Jalmuzna, A. Napieralski
    TUL-DMCS, Lodz
  • L. Lilje, K. P. Przygoda, S. Simrock
    DESY, Hamburg
  • R. P. Paparella
    INFN/LASA, Segrate (MI)
  Funding: We acknowledge the support of the ECRIA under the FP6 program (CARE, contract number RII3-CT-2003-506395), and Polish National Science Council Grant "138/E-370/SPB/6. PR UE/DIE 354/2004-2007"

The SC cavities need a fast tuning system, which is able to adjust the shape during the pulse operation. The first attempts were focused on the compensation of the repetitive and periodic distortion. The algorithms were implemented in Matlab and allow compensating only the Lorentz force detuning. However, the previous solution was too slow to be able to compensate the microphonics. The paper presents recent development in the field. The previously worked out algorithms are implemented in the FPGA-based control system. The SIMCON board is used, which allows to perform parallel, deeply pipelined calculation. The new approach allows integrating the algorithm dedicated for cavity shape control with the LLRF system used for vector sum control. Moreover, the new algorithm for on-line detuning calculation which base on the electromechanical model of the cavity is presented. The system is tested with Module Test Stand (MTS) at DESY with the high gradient cavities (37 MV/m). The active elements are the NOLIAC's and PI's multilayer, low voltage piezostacks. The paper will present the first results from these measurements.

TUZAC01 The ILC Control System Design 868
  • J. Carwardine, N. D. Arnold, F. Lenkszus, C. W. Saunders
    ANL, Argonne, Illinois
  • B. Banerjee, B. Chase, E. G. Gottschalk, P. W. Joireman, P. A. Kasley, J. R. Lackey, P. M. McBride, J. F. Patrick, V. Pavlicek, M. Votava, S. A. Wolbers
    Fermilab, Batavia, Illinois
  • R. W. Downing, R. S. Larsen
    SLAC, Menlo Park, California
  • K. Furukawa, S. Michizono
    KEK, Ibaraki
  • K. Rehlich, S. Simrock
    DESY, Hamburg
  Funding: Work supported in the U. S. by the U. S. Department of Energy under contract Nos. DE-AC02-06CH11357, DE-AC02-76CH03000, and DE-AC02-76SF00515.

The scale and performance parameters of the ILC require new thinking in regards to control system design. This design work has begun quite early in comparison to most accelerator projects, with the goal of uniquely high overall accelerator availability. Among the design challenges are high control system availability, timing reference distribution, standardization of interfaces, operability, and maintainability. We present the current state of the design and take a prospective look at ongoing research and development projects.

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FROAC06 Survey of LLRF Development for the ILC 3810
  • J. Branlard, B. Chase
    Fermilab, Batavia, Illinois
  • S. Michizono
    KEK, Ibaraki
  • S. Simrock
    DESY, Hamburg
  Funding: FRA

The key to a successful LLRF design for the International Linear Collider (ILC) relies on a combined effort from the different laboratories involved in this global project. This paper covers the ILC LLRF design progress both long term and for current test facilities around the world. Much of the focus is towards the ILC Test Area and on inter-laboratories collaborations. The SIMCON controller board, originally developed at DESY has been successfully used at FNAL to control the superconducting capture cavity I and II. A joined effort is also underway to modify its hardware to improve its noise performance and upgrading the firmware to achieve a higher intermediate frequency operation. In parallel, several simulation models (U-Penn, FNAL) have been developed in addition to the Simulink based model from DESY. The motivation is to investigate such issues as variable gradients, low beam conditions and bunch compression. Finally, an active exchange of knowledge and expertise continues to occur during collaboration meetings and through mutual participation in accelerator tests and commissioning (Dec06/Jan07 at DESY).

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