Stefan Simrock

Distributed embedded-PC-based control and data acquisition system for TESLA cavity controller and simulator

This paper describes an alternative approach for control and data acquisition system to be used in TESLA controller and simulator (SIMCON) boards. The standard VME controller may be replaced with a cheap embedded PC to provide equivalent or even superior functionality. The new approach offers better cost/performance ratio, better scalability of the system and better testability of the SIMCON boards.

Cavity control system essential modeling for TESLA linear accelerator

The pioneering TESLA linear accelerator and free electron laser project is initially introduced. Elementary analysis of cavity resonator with signal and power considerations is presented. Two alternative simulation models of cavity control system are proposed.

Prototype AdvancedTCA Carrier Board with three AMC bays

The Low Level RF (LLRF) control system of the Free Electron Laser in Hamburg (FLASH) is currently based on the Versa Module EuroCard (VME) standard. However, the application of Advanced Telecommunications Computing Architecture (ATCA) platform, as an alternative to the above mentioned standard, is taken into consideration. ATCA offers most of all improved reliability, because of the integrated management system which controls crucial parameters of the whole platform and provides the operator with control and diagnostics over the system from an external personal computer. Furthermore, implementation of AdvancedTCA architecture results in significant system operability enhancement, due to instant detection of a faulty module and Hot-Swap functionality that enables a swift replacement of the module, without disrupting the whole system. The platform management is under control of the Intelligent Platform Management Interface (IPMI). The paper presents the IPMI software for the Intelligent Platform Management Controller (IPMC) on a prototype Carrier Board. The software covers most of the functionality, defined by AdvancedTCA and IPMI ver. 1.5 standards, including inter alia sensor monitoring, platform event handling, communication with the Shelf Manager and complete activation and deactivation processes not only for the Carrier Board, but also for three attached Advanced Mezzanine Card (AMC) modules. In the future, the software is going to be implemented on the ATCA test boards for LLRF control systems of the FLASH. The application of AdvancedTCA architecture with IPMI functionality in the control system of the X-Ray Free Electron Laser (X-FEL) is considered, as well. Both lasers are situated at Deutsches Elektronen Synchrotron DESY, Hamburg, Germany.

Cavity Control System - Optimization Methods For Single Cavity Driving and Envelope Detection.

The paper is an introduction to the optimization methods of the linear accelerator cavity control system. Three distinct time periods of cavity operation are considered; filling with the EM field energy, field stabilization, and field decay. These periods represent completely different states and behavior of the cavity. The cavity could be operated by several different methods in each work phase: During the filling -- feedback and feed-forward alone, feedback and feed-forward together, self-tuning; During the flattop -- feed-forward and feedback alone or together, During the decay -- detuning and quality factor may be measured. The optimization is understood as a choice of the most efficient way of the cavity control during each period. The control may be done in terms of minimum power consumption from the klystron during whole work cycle and efficient field stabilization in the cavity, during flattop period. The introductory analysis of the cavity operational modes in three mentioned periods is presented in this paper. Additionally the alternative more precise algorithm of the cavity voltage envelope detection is proposed.

Cavity digital control testing system by Simulink step operation method for TESLA linear accelerator and free electron laser

The cavity control system for the TESLA -- TeV-Energy Superconducting Linear Accelerator project is initially introduced in this paper. The FPGA -- Field Programmable Gate Array technology has been implemented for digital controller stabilizing cavity field gradient. The cavity SIMULINK model has been applied to test the hardware controller. The step operation method has been developed for testing the FPGA device coupled to the SIMULINK model of the analog real plant. The FPGA signal processing has been verified according to the required algorithm of the reference MATLAB controller. Some experimental results have been presented for different cavity operational conditions.

First demonstration of microphonic control of a superconducting cavity with a fast piezoelectric tuner

Superconducting cavities exhibit a high susceptibility to mechanical vibrations due to their narrow bandwidth of operation. The resulting modulation of the resonance frequency (typical amplitudes are, in the absence of mechanical dampers, a few tens of Hz at a modulation frequency of up to a few hundred Hz) can exceed the cavity bandwidth leading to a perturbation of the amplitude and phase of the accelerating field, which can be controlled only at the expense of rf power. It is therefore highly desirable to control the resonance frequency of the cavity with a fast controller. A fast mechanical tuner based on piezoelectric or magnetostrictive actuator appears very attractive, since its tuning is done simply by a micrometric deformation of the resonator geometry. In the past these tuners have been limited by mechanical resonances in the transfer function to a modulation bandwidth of about 1 Hz. With modem control theory and high speed DSPs and FPGAs it is now possible to design complex controllers which allow high gain up to several hundred Hz. In this paper we present first results of fast microphonics piezoelectric control for a superconducting quarter wave resonator. Microphonics at 42 Hz (inner conductor) are controlled despite a large mechanical resonance a 662 Hz in the actuator transfer function.

Design and simulation of FPGA implementation of a RF control system for the TESLA test facility

This paper presents a new FPGA based solution of the Low Level RF Control System for TESLA Test Facility. The LLRF Control System is responsible for maintaining the constant amplitude and phase of accelerating field in set of accelerators cryomodulaes driven by single klystron. To obtain shorter processing time and less complicated hardware an FPGA based solution was selected. The proposed simulation has been simulated in software, and appeared to be faster and less complex than DSP based solutions.

RF Control System for the DESY VUV-FEL Linac

In the RF system for the Vacuum Ultraviolet Free Electron Laser (VUV-FEL) Linac each klystron supplies RF power to up to 32 cavities. The superconducting cavities are oper ated in pulsed mode and high accelerating gradients close to the performance limit. The RF control of the cavity fields to the level of 10-4for amplitude and 0.1 degree for phase however presents a significant technical chal lenge due to the narrow bandwidth of the cavities which re sults in high sensitivity to perturbations of the resonance frequency by mechanical vibrations (microphonics) and Lorentz force detuning. A digital RF control system has been developed for the VUV-FEL which will demonstrate the required control performance. Presently the Linac is being commissioned, and this effort provides the first full integrated test in the accelerator, including cryogenics, RF, beam transport, and beam diagnostics. The RF control sys tem design and objectives are discussed.

Application of SysML to design of ATCA based LLRF control system

The paper presents the methodology of design of ATCA based LLRF system for XFEL linear accelerators. The LLRF system is used to control RF field in superconducting accelerating cavities regulating amplitude up to 0.03% and phase up to 0.03 deg. It is complex mixed analogue-digital control with latency of order of few tens of nanoseconds. The ATCA architecture was chosen due to high availability and reliability. The system design process is based on systematic and formal approach using SysML language and tools. This modern methodology changes the way of system description from “document centric” to “model centric”. It allows easy communication inside the designers team that is very important in wide international collaboration. In the design process the Use Case description of system functionality was applied. The hierarchical structure and requirements for subsystems was derived from the top level requirements and defined functionality of the system. The functions of various SysML diagrams are presented together with discussion which parts of the system are best described by which diagram type. Both structural and functional views of the system are presented. Since the discussed LLRF system will have distributed architecture the particular effort was put on interfaces description. The SysML tool used in the project was used not only to build SysML model but also allows to estimate project cost using Use Case Points method. This feature is very beneficial in preparation of the project budget.

FPGA-based multichannel optical concentrator SIMCON 4.0 for TESLA cavities LLRF control system

The paper presents an idea, design and realization of a gigabit, optoelectronic synchronous massive data concentrator for the LLRF control system for FLASH and XFEL superconducting accelerators and lasers. The design bases on a central, large, programmable FPGA VirtexIIPro circuit by Xilinx and on eight commercial optoelectronic transceivers. There were implemented peripheral devices for embedded PowerPC block like: memory and Ethernet. The SIMCON 4.0 module was realized as a single, standard EURO-6HE board with VXI/VME-bus. Hardware implementation was described for the most important functional blocks. Construction solutions were presented.