| Paper | Title | Page |
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| TUPC141 | Concept and Implementation of the SC Cavity Resonance Frequency Monitor for the Digital RF Field Controller | 1398 |
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| New generations of digital control systems offer large number of computation resources together with precise ADCs (analog to digital converters) and DACs (digital to analog converters) which can be used to generate almost any klystron driving signal. This gives the possibility to implement such features as digital SEL (self excited loop) and frequency sweep mode. They can be used to monitor resonance frequency of SC cavities. This information can be used by tuning system to adjust cavity tuner settings. Such functionality is valuable especially during the first RF station start up when the cavities may be detuned even by a large frequency. The paper presents the concept of such system and summarizes implementation and tests performed at FLASH facility (DESY, Hamburg). | ||
| TUPC142 | Performance of 24 Cavity Vector Sum Controller with Distributed Architecture | 1401 |
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| The paper presents the test results of the digital vector sum control applied for 24 superconducting cavities driven by 1 klystron. The controller is based on FPGA chips and consists of multiple processing boards which communicate via optical fiber links. Flexible and scalable distributed architecture was designed and implemented to provide framework for the control algorithms. The tests were performed at FLASH (DESY, Hamburg) facility using ACC4, ACC5 and ACC6 modules. Results were compared to the existing DSP based system. | ||
| TUPC145 | FPGA Implementation of Multichannel Detuning Computation for SC Linacs | 1410 |
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| The paper presents a multi-cavity system for active compensation of SC cavities' deformations in linear accelerators like Free Electron Laser. Described system consists of digital controller, analog amplifiers and mechanical actuators. The previously developed control algorithms were implemented in SIMCON 3.1 board and allow online calculations of Lorentz force detuning only for one cavity. The recent development in the field is based on serial pipelined computations which allow a real time detuning measurements of 8 and more cavities. Moreover, the SIMCON DSP board was used for 10 ns latency computations. The new approach enables integrating the algorithm dedicated for cavity shape control with the LLRF control system using optical transmission. Furthermore the 8-channels amplifiers have been successfully added to the compensation system for driving the piezoelectric actuators. The system is tested in FLASH at DESY. The accelerating modules ACC 3, 5 and 6 with high operating gradients cavities have been taken into account. The multilayer piezostacks from PI and NOLIAC are used for the compensation purpose of cavities' deformations. | ||
| TUPC146 | Real Time, Distributed, Hardware-software Simulation of Multicavity RF Station for LLRF System Development in FLASH and XFEL | 1413 |
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| The paper describes the implementation of distributed (FPGA, DSP, GPP) system for simulation of multiple TESLA cavities together with high power distribution chain. The applied models simulate the system behavior with the performance close to the response time of the real RF station and cryomodules. Parametrized architecture of the simulator allows to find compromise between the features of the model and the available resources it can be implemented in. The results of driving the simulator using the FLASH LLRF system are presented and compared with the real measurements. Proposed solution is the important tool for LLRF system development and testing, and can be, in many cases, a replacement for the tests in the real superconducting test facilities reducing the development costs and time. | ||
| TUPP003 | Automatic Generation of SEU Immunity for FPGA Based Electronics for Accelerators | 1529 |
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The modern accelerator control systems nowadays are build using digital technology based on FPGA circuits. However, digital circuits working in radioactive environment are exposed to disturbing effects, in particular SEU (Single Event Upset)*. One of the countermeasure is a redundancy in circuit that allow to detect and correct errors caused by radiation**. Unfortunately CAD software provides no support to automatically include required redundancy in the FPGA project. Moreover, optimization procedure removes all redundant parts and special effort must be made to prevent that. The paper presents a software environment to process VHDL description of the circuit and automatically generate the redundant blocks together with voting circuits. The generated redundancy uses Triple Module Redundancy (TMR) scheme. It also supports the VHDL simulation with SEUs in order to enable identification of the most sensitive components***. Since the TMR is costly, the designer can indicate which parts of the circuit should be replicated based on the results of simulation.
*Baumann. Neutron-induced…, Int. Rel. Phys. Symp. 2000. |
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| THPC158 | Measurement and Stabilization of the Bunch Arrival Time at FLASH | 3360 |
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| To fully exploit the experimental opportunities offered by the 10 - 30 fs long light pulses from FLASH, e.g. in pump-probe experiments, precise measurements and control of the electron-bunch arrival-time on the 10 fs scale are needed. A bunch arrival time monitor (BAM) which uses the optical synchronization system of FLASH as a reference has been developed for this purpose. The bunch induced signal from a GHz-bandwidth beam pick-up is guided into an electro-optical modulator in which the periodic laser pulse train of the optical synchronization system experiences an amplitude modulation. Detection of this modulation allows to determine the bunch arrival time with a resolution of better than 20 fs. The superconducting linac of FLASH generates trains of up to 800 bunches. The BAM signals can be used for an intra-bunch train feedback stabilizing the arrival time to better than 50 fs. The feedback is capable of generating well-defined arrival time patterns within a bunch train which are useful for overlap-scans in pump-probe experiments. First results from the feedback installed at FLASH will be presented. |