| Paper |
Title |
Page |
| THP001 |
Conceptual LLRF Design for the European X-FEL
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559 |
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- S. Simrock, V. Ayvazyan, A. Brandt, M. Huening, W. Koprek, F. Ludwig, K. Rehlich, E. Vogel, H. C. Weddig
DESY, Hamburg
- M. K. Grecki, T. Jezynski
TUL-DMCS, Lodz
- W. J. Jalmuzna
Warsaw University of Technology, Institute of Electronic Systems, Warsaw
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The LLRF System for the superconducting cavities of the European X-FEL must support an amplitude and phase stability of the accelerating fields of up to 0.01% and 0.01 deg. respectively. The stability must be achieved in pulsed operation with one klystron driving 32 cavities. This goal can only be achieved with low noise downconverters for field detection, high gain feedback loops and sophisticated feedforward techniques. State-of-the art technology including analog multipliers for downconversion, fast ADCs (>100 MHz) with high resolution (up to 16 bit), and high performance data processing with FPGAs with low latency (few hundred ns) allow to meets these goals. The large number of input channels ( >100 including probe, forward and reflected signal of each of the 32 cavities) and output channels (>34 including piezo tuners for each cavity) combined with the tremendous processing power requires a distributed architecture using Gigalink interfaces for low latency data exchange.
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| THP002 |
Exception Detection and Handling for Digital RF Control Systems
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562 |
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- S. Simrock, V. Ayvazyan, M. G. Hoffmann, M. Huening, W. Koprek, K. Rehlich, E. Vogel
DESY, Hamburg
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Exception detection and handling routines will play an important role in future large scale accelerator to ensure high availability and beam stability in presence of interlock trips, varying operational parameters, and operation close to the performance limit. For superconducting linacs typical examples for exception situations include cavity quenches, coupler and klystron gun sparcs, operation close to klystron saturation, and errors in vector-sum calibration. The goal is to identify all possible exception situations which will lead to performance degradation or downtime, detect these situations and take appropriate actions as necessary.
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| THP003 |
Integrated Optical Timing and RF Reference Distribution System for Large-Scale Linear Accelerators
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565 |
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- A. Winter, J. Becker, F. Loehl, K. Rehlich, S. Simrock
DESY, Hamburg
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Highly-stable timing and RF reference distribution systems are required to meet the tight specifications in large scale accelerators for next generation light sources. In this paper, we present an approach based on the distribution of an optical pulse train from a mode-locked laser via timing stabilized fiber links. The timing information is contained in the precise repetition rate of the optical pulse train (~50 MHz), so RF can be extracted at end stations with a stability on the order of 10 fs. Less timing critical signals such as ADC clocks and trigger signals can be transmitted through the same stabilized fiber using a modulated cw laser operating at a different wavelength with sub-ps stability. As multiple wavelengths can propagate without interference through the fiber, it is also possible to integrate data communication in such a fiber system. This paper will review the timing system requirements and present a conceptual layout of an optical timing and reference frequency distribution system based on work done at MIT and DESY for the XFEL.
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| THP013 |
Adaptive Control of a SC Cavity Based on the Physical Parameters Identification
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595 |
| |
- T. Czarski, W. J. Jalmuzna, W. Koprek, K. T. Pozniak, R. S. Romaniuk
Warsaw University of Technology, Institute of Electronic Systems, Warsaw
- S. Simrock
DESY, Hamburg
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The paper presents preliminary results of SRF cavity control by FPGA system called "SIMCON". Algebraic model of the control system including calibration and correction procedure of the signal path was discussed. In particular, there were debated the following aspects of the automatic control procedures: compensation of the input offset, calibration of the cavity channel and correction of the klystron channel (linearization). Functional structure of FPGA based SIMCON board for LLRF Cavity Control System was explained. Alghoritm of adaptive control for cavity driven with FPGA controller supported by MATLAB system was discussed. Experimental results for 8 cavities of ACC1 module controlled by the SIMCON board were shown. The resuls lead to novel method of parameters identification of cavity system in noisy and no stationary conditions.
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| THP097 |
FPGA BASED DIGITAL RF CONTROL FOR FLASH
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809 |
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- W. J. Jalmuzna, P. F. Fafara, W. Koprek, P. K. Perkuszewski, K. T. Pozniak, P. Pucyk, R. S. Romaniuk
Warsaw University of Technology, Institute of Electronic Systems, Warsaw
- S. Simrock
DESY, Hamburg
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Most parts of the LLRF control system used in FLASH are based on the DSP processors. Actual computation power of the system is close to the limit, the algorithm is performed in a time longer than 1μs. The only way to extend the system with new features was to add more DSP processors. This solution requires integration of new DSP board into existing system. It may cause some additional problems and delays in the machine operations. During past years very fast progress on the FPGA market was observed. Nowadays FPGA chips have reached the computation power that can be compared with DSP processors. These chips offer variety of the embedded solutions such as PowerPC, Microblaze, Nios which can be easily used in addition to fast, parallel signal processing. Moreover large number of user pins makes it possible to integrate all the elements necessary for the control into one PCB board. Therefore, for the evaluation purposes, some parts of the system were replaced by FPGA based boards. This article summarizes the FPGA boards that are currently in use and describes algorithms executed by these boards.
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