EPAC08 - Classification:07 Accelerator Technology Main Systems/T25 Low Level RF

07 Accelerator Technology Main Systems

T25 Low Level RF

Paper	Title	Page
TUPC138	Development of a New Low-Level RF-Control-System for the S-DALINAC	1389
	A. Araz, U. Bonnes, R. Eichhorn, M. Konrad, M. Platz, A. Richter TU Darmstadt, Darmstadt U. Laier GSI, Darmstadt R. Stassen FZJ, Jülich
	The Superconducting DArmstadt electron LINear ACcelerator S-DALINAC has a maximum energy of 130 MeV and beam currents of up to 60 μA. To reach this energy conveniently in cw, superconducting cavities with a high Q at a frequency of 3 GHz are used. In order to achieve minimal energy spread, the amplitude and phase the cavities have to be controlled strictly in order to compensat the impact of microphonic perturbations. The existing analog rf control system based on a self-exited loop, converts the 3 GHz signals down to the base band. This concept will also be followed by the new digital system currently under design. It is based on an FPGA in the low frequency part, giving a great flexibility in the control algorithm and providing additional diagnostics. For example it is possible to change the operational mode between self-exited loop and generator driven resonator within a second. We will report on the design concept, the status and the latest results measured with a prototype, including different control algorithms as well as beam loading effects.
TUPC139	LLRF Electronics for the CNAO Synchrotron	1392
	O. Bourrion, D. Tourres, C. Vescovi LPSC, Grenoble
	The Italian National Centre for Oncological hAdrontherapy (CNAO) is undergoing its final construction phase in Pavia and will use proton and carbon ion beams to treat patients affected by solid tumours. At the hearth of CNAO is a 78 meters circumference synchrotron, capable of accelerating particle up to 400 MeV/u with a repetition rate of 0.4 Hz. Particle acceleration is done by a unique VITROVAC load RF cavity operating at a frequency between 0.3 and 3MHz and up to 3kV peak amplitude. In order to control this cavity a digital LLRF system has been designed at LPSC. It is based mainly upon Digital Signal Processors (DSPs), Field Programmable Gate Arrays (FPGA) and Direct Digital Synthesizers (DDS). The LLRF system implement both cavity control and beam control capabilities in a compact, remotely programmable and configurable, Ethernet controlled electronic module. It also allows an easy regulation loop tuning, thanks to an embedded acquisition system that stores all input and output signals during a given acceleration cycle. This paper describes the electronics architecture, lab measurements and test results obtained with the system coupled with the CNAO cavity.
TUPC140	The Spallation Neutron Source Cryomodule Test Stand RF System	1395
	M. T. Crofford, T. W. Hardek, D. Heidenreich, Y. W. Kang, K.-U. Kasemir, S.-H. Kim ORNL, Oak Ridge, Tennessee J. A. Ball, T. L. Davidson ORNL RAD, Oak Ridge
	The Spallation Neutron Source (SNS) has recently commissioned a cryomodule test facility for the repair and testing of the super-conducting cryogenic cavities. This facility utilizes the original 402.5/805 MHz Radio Frequency (RF) Klystron Test Stand as its power source along with dual Low Level RF (LLRF) control systems. One control system is based on the standard SNS Linac LLRF controls with a second system for open-loop only control. The system is designed to allow simultaneous testing of devices in the test cave and other devices which can be tested outside of the enclosure. Initial tests have shown good results; some improvements are yet to be implemented. This paper will provide an overview of the RF systems, safety systems, and interlocks.
TUPC141	Concept and Implementation of the SC Cavity Resonance Frequency Monitor for the Digital RF Field Controller	1398
	W. Jalmuzna, A. Napieralski TUL-DMCS, Łódź S. Simrock DESY, Hamburg
	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
	W. Jalmuzna, A. Napieralski TUL-DMCS, Łódź
	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.
TUPC143	Precise RF Control System of the SCSS Test Accelerator	1404
	H. Maesaka, T. Fukui, N. Hosoda, T. Inagaki, T. Ohshima, Y. Otake, H. Tanaka RIKEN/SPring-8, Hyogo T. Hasegawa, S. Takahashi, S. Tanaka JASRI/SPring-8, Hyogo-ken M. K. Kitamura NDS, OSAKA
	We present the development and performance of the low level rf control system of SCSS test accelerator (VUV-FEL facility). The FEL radiation in the wavelength region of 50-60 nm reached saturation in fall 2007. Since then, the FEL intensity fluctuation has been suppressed within 10%. This performance was achieved by stabilizing the rf phase and amplitude of the accelerator. For example, the rf phase stability of the 238 MHz cavity is achieved to be 0.03 degree rms corresponding to 350 fs. Those of other cavities such as C-band (5712MHz) accelerator are also obtained to be several 100 fs. To control the rf phase and amplitude precisely, we have developed an IQ modulator / demodulator system. To treat the baseband signal of the system, we have also developed VME high speed DAC / ADC boards. The phase skew of the IQ system is ± 1.0 degree without correction and ± 0.1 degree after correction. To suppress the slow drift of rf components, we applied a PID feedback control loop to the rf source and cavity system. We also improved temperature stabilization for the acceleration structures.
TUPC144	Digital Low Level RF System for SOLEIL	1407
	P. Marchand, M. D. Diop, F. Ribeiro, R. Sreedharan SOLEIL, Gif-sur-Yvette M. Luong, O. Piquet CEA, Gif-sur-Yvette
	In the SOLEIL storage ring, two cryomodules, each containing a pair of 352 MHz superconducting cavities, will provide the maximum power of 560, required at the nominal energy of 2.75 GeV with the full beam current of 500 mA. Presently, an analogue Low Level RF system is successfully operating to control the amplitude and phase of the accelerating voltage. A fast digital FPGA based I-Q feedback is currently under development. The digital I-Q loop is realised with a HERON IO2 FPGA module using a Virtex II with 1M gates. The performance of the digital LLRF system has been evaluated using a Matlab-Simulink based simulation tool taking into account different features (loop delays, bandwidth limitation, extra power budget). The hardware design is described and the first experimental results are reported.
TUPC145	FPGA Implementation of Multichannel Detuning Computation for SC Linacs	1410
	K. P. Przygoda, J. Andryszczak, W. Jalmuzna, A. Napieralski, T. Pozniak TUL-DMCS, Łódź
	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
	P. Pucyk, S. Simrock DESY, Hamburg W. Jalmuzna TUL-DMCS, Łódź
	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.
TUPC147	Analogue LLRF for the ALBA Booster	1416
	H. Hassanzadegan, F. Pérez ALBA, Bellaterra
	ALBA Booster will inject up to 2 mA of current, at 3 Hz, in the 3 GeV 3rd generation Synchrotron Light Source ALBA, that is in the construction phase in Cerdanyola, Spain. The Booster will ramp the beam energy from 100 MeV to 3 GeV, the RF voltage will be ramped as well from <100 kV to 1 MV to improve injection efficiency and maintain the beam stable. The Booster RF System will have to provide up to 1 MV of accelerating voltage and have a high dynamic range. An Analogue LLRF prototype has been developed for the Booster 5 cell RF Cavity. The prototype is based on the IQ modulation/demodulation technique and it has been designed completely in house. The prototype has been installed in the high power RF lab of CELLS and tested to control up to 80 kW on the real Booster Cavity. The test results of the control loops (amplitude, phase and tuning) will be presented, as well as the hardware structure and the system interface.
TUPC148	Digital LLRF for ALBA Storage Ring	1419
	A. Salom, F. Pérez ALBA, Bellaterra
	ALBA is a 3 GeV, 400 mA, 3rd generation Synchrotron Light Source that is in the construction phase in Cerdanyola, Spain. The RF System will have to provide 3.6 MV of accelerating voltage and restore up to 540 kW of power to the electron beam. A Digital LLRF prototype has been developed for the Storage Ring RF Cavity. The prototype is based on the IQ modulation/demodulation technique and it has been implemented using a commercial FPGA cPCI board. The prototype has been installed in the high power RF lab of CELLS and tested to control up to 80 kW on the real Storage Ring Cavity. The test results of the control loops (amplitude, phase and tuning) will be presented, as well as the hardware structure (digital boards, analogue front ends, timing, etc.) and the system interface.
TUPC150	Ensemble Cavity Control System Simulation Using Pulse-to-pulse Calibration	1422
	C. Serrano, L. R. Doolittle, A. Ratti, A. Vaccaro LBNL, Berkeley, California
	For cost reasons one klystron will supply RF power to multiple cavities in recent projects. Individual cavity field stability and optimal drive needs to be achieved considering beam propagation, cavity tuning, cavity coupling, and cable lengths. External environmental factors continuously modify physical properties of the accelerating structures and waveguides. Therefore a calibration system has been designed to adapt individual drive signals and vector-sum alignment in a pulse-to-pulse basis. An eight-cavity model and a calibration system have been tested in simulation using the hardware-software simulation tool developed at LBNL.
TUPC151	Universal DOOCS Server Based on the Scripting Language	1425
	J. Szewinski, K. Korzunowicz Warsaw University of Technology, Institute of Electronic Systems, Warsaw
	This document describes the design and implementation of the universal DOOCS* server based on the script language for the FLASH accelerator in DESY (Hamburg, Germany). Server works with the DOOCS, which is used in FLASH for machine control. The typical usage of this application is to communicate with the measurement equipment and control small facilities of the accelerator. The aim of the project is to provide a tool which can make the server creation easy for non-programmer users (typically physicists). The heart of the server is the script language parser which has been done using well known UNIX tools: bison and flex. The complexity of designed language is comparable with complexity of the Matlab language. Application has additional features like possibility of attaching external dynamic libraries or possibility of defining the state machines (more sequencer like). Server has been tested at FLASH and currently is used by people who wish to control their equipment via DOOCS, with the minimal effort of software development. *Distributed Object Oriented Control System.
TUPC153	Hardware-software Simulation for LLRF Control System Development	1428
	A. Vaccaro, L. R. Doolittle, A. Ratti, C. Serrano LBNL, Berkeley, California
	Field Programmable Gate Arrays (FPGA) have been used in accelerator controls for a long time. Stricter performance requirements in new accelerator designs force LLRF control systems to continuously improve, and the increasing density of available FPGAs enables such progress. The increased complexity in FPGA design is not always followed by new RF systems availability for development and testing. Therefore, a hardware-software simulation tool has been developed to model RF systems by a software simulator. It simulates the interaction of HDL code that is to be synthesized with both RF systems and communication ports to external controls software, reproducing realistic working conditions of the FPGA. The hardware-software interaction for LLRF control system design is discussed here.
TUPC154	CERN PSB Beam Tests of CNAO Synchrotron's Digital LLRF	1431
	M.-E. Angoletta, A. Findlay CERN, Geneva O. Bourrion, R. Foglio, D. Tourres, C. Vescovi LPSC, Grenoble C. De Martinis INFN-Milano, Milano L. Falbo, S. Hunt CNAO Foundation, Milan
	The Italian National Centre for Oncological hAdrontherapy (CNAO), in its final construction phase, uses proton and carbon ion beams to treat patients affected by solid tumours. At the heart of CNAO is a 78-meter circumference synchrotron that accelerates particles to up to 400 MeV/u. The synchrotron relies on a digital LLRF system based upon Digital Signal Processors (DSPs) and Field Programmable Gate Array (FPGA). This system implements cavity servoing and beam control capabilities, such as phase and radial loops. Beam tests of the CNAO synchrotron LLRF system were carried out at CERN’s Proton Synchrotron Booster (PSB) in autumn 2007, to verify the combined DSP/FPGA architecture and the beam control capabilities. For this, a prototype version of CNAO’s LLRF system was adapted to the PSB requirements. This paper outlines the prototype system layout and describes the tests carried out and their results. In particular, system architecture and beam control capabilities were successfully proven by comparison with the PSB operational beam control system and with the help of several existing beam diagnostic systems.
WEOBM02	Lessons Learned from PEP-II LLRF and Longitudinal Feedback	1953
	J. D. Fox, T. Mastorides, C. H. Rivetta, D. Van Winkle SLAC, Menlo Park, California D. Teytelman Dimtel, San Jose
	The PEP-II B Factory is in the final phase of operation at 2X the design current and 4X the design luminosity. Since the original design the machine has added 8 1.2 MW Klystrons and 12 RF cavities, and the machine is operating with longitudinal instability growth rates roughly 5X in excess of the original estimates. Since commissioning there has been continual adaptation of the LLRF control strategies, configuration tools and new hardware in response to unanticipated technical challenges. This paper presents the LLRF and feedback system evolution from the original design estimates through to the 1.2·10³⁴ final machine. We highlight issues of RF station stability, the interplay of LLRF configuration and low-mode (cavity fundamental driven) longitudinal instabilities, impacts of non-linearities and imperfections in the LLRF electronics, control of HOM driven beam instabilities and the development of configuration tools and measurement techniques to optimally configure the LLRF over the wide range of operating currents. We present valuable "lessons learned" which are of interest to designers of next generation impedance controlled LLRF systems.
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