• N. Kamikubota, S. Yamada
  KEK, Ibaraki
• T. Iitsuka, S. Motohashi, M. Takagi, S.Y. Yoshida
  Kanto Information Service (KIS), Accelerator Group, Ibaraki
• H. Nemoto
  ACMOS INC., Tokai-mura, Ibaraki
• N. Yamamoto
  J-PARC, KEK & JAEA, Ibaraki-ken

The beam commissioning of the J-PARC Main Ring started in May, 2008. Data archive system has been developed using Channel Archiver, which is a tool developed and maintained in the EPICS community. Various machine parameters and status information of Main Ring have been recorded. The number of records registered extends 17,000 as of December, 2009. The archive data can be retrieved in a form of graphical representation by Web browser. In addition, the mechanism to provide bit-type information, such as interlock and on/off, in time series format is available. They have been used in daily operation of Main Ring. Addition to them, we are trying to develop a new scheme to record large waveform data of beam diagnostic signals. Status and progress of the archive system will be discussed.

• T.T. Nakamura, A. Akiyama, K. Furukawa
  KEK, Ibaraki

Most of the magnet power supplies of the KEKB rings and beam transport lines are connected to the local control computers through ARCNET. For this purpose we have developed the Power Supply Interface Controller Module (PSICM), which is designed to be plugged into the power supply. It has a 16-bit microprocessor, ARCNET interface, trigger pulse input interface, and parallel interface to the power supply. According to the upgrade plan of the KEKB accelerators, more power supplies are expected to be installed. Although the PSICMs have worked without serious problem for 11 years, it seems too hard to keep maintenance for the next decade because some of the parts have been discontinued. Thus we decided to develop the next generation of the PSICM. Its major change is the use of the Ethernet instead of the ARCNET. On the other hand the specifications of the interface to the power supply are not changed at all. The new PSICM is named ePSICM (Ethernet-based Power Supply Interface Controller Module). The design of the ePSICM and the development of the prototype modules are in progress.

• J.-I. Odagiri, K. Akai, K. Furukawa, S. Michizono, T. Miura, T.T. Nakamura
  KEK, Ibaraki
• H. Deguchi, K. Hayashi, J. Mizuno, M. Ryoshi
  Mitsubishi Electric TOKKI Systems, Amagasaki, Hyogo

Gazing at SuperKEKB project, a new control subsystem was designed and implemented to upgrade the low level RF system of the KEKB accelerator based on Experimental and Industrial Control System (EPICS). The new control subsystem comprises a uTCA, a PLC, and an industrial PC. Each card plugged in the uTCA chassis and the PLC function as an embedded Input / Output Controller (IOC) by running the EPICS core program on the Linux operating system. The industrial PC runs Extensible Display Manger on Linux to serve as an Operator Interface (OPI). This paper describes the details of the design and the implementation of the fully embedded EPICS-based low level RF control subsystem for SuperKEKB.

• N. Yamamoto
  KEK, Ibaraki

VXI-11 is an industrial standard to control equipments through network. A moule to control these equipments through Python scripting Language was developed. This module can be used for quick testing of equipments and for the rapid application development. The implementation of the module will be discussed and some application of the module will be reported.

• J. Takano, T. Koseki, S. Nakamura, T. Toyama, N. Yamamoto
  J-PARC, KEK & JAEA, Ibaraki-ken
• S. Hatakeyama
  JAEA/J-PARC, Tokai-mura
• K. Niki, M. Tomizawa, S. Yamada
  KEK, Ibaraki

In the J-PARC Main Ring (MR), the bending, quadrupole, sextupole, and steering magnets can be controlled on the operating interfaces (OPI). The optics parameters for all magnets are calculated by using SAD, and are converted to BL tables (ex: 2000 points for a steering magnet) for each power supplies. The BL tables are made from the parameters of optics, pattern timing, and beam energy at flat bottom and flat top. For MR beam studies, the BL tables are adjustable with offset and factor. This system is useful for COD correction, beta function measurement, aperture survey, and slow extraction. In this proceeding, the structure of the magnet control system and OPIs for beam studies will be shown.

• H. Takahashi, T. Kojima, S. Maebara, T. Narita, H. Sakaki, K. Tsutsumi
  JAEA, Rokkasho, Kamikita, Aomori

Control System for IFMIF/EVEDA accelerator prototype consists of the six subsystems; Central Control System (CCS), Local Area Network (LAN), Personnel Protection System (PPS), Machine Protection System (MPS), Timing System (TS) and Local Control System (LCS). The subsystems have been designed and their test benches been fabricated at JAEA. The IFMIF/EVEDA accelerator prototype provides a deuteron beam with the power more than 1 MW, which is as same as that in cases of J-PARC and SNS. In the control system, MPS and TS with high performance and precision are strongly required to avoid the radio-activation of the accelerator components. The prototypes of the MPS and TS are testing in conjunction with the injector test starting at CEA/Saclay from autumn in 2010. These results will feedback the design and the fabrication of the control components. This paper presents the development status of the TS modules and EPICS drivers for TS and MPS, and the prospects to apply them to the Injector test.

• S. Hatakeyama, N. Hayashi
  JAEA/J-PARC, Tokai-mura
• D.A. Arakawa, Y. Hashimoto, S. Hiramatsu, J.-I. Odagiri, M. Tejima, M. Tobiyama, T. Toyama, N. Yamamoto
  KEK, Ibaraki
• K. Hanamura
  MELCO SC, Tsukuba
• K. Satou
  J-PARC, KEK & JAEA, Ibaraki-ken

The Data Acquisition System of Beam Position Monitors(BPMs) in J-PARC Main Ring are consist of 186 Linux-based Data Processing Cirquits(BPMCs) and 12 EPICS IOCs. They are important tool to see the COD and turn-by-turn beam positions. This report describes the process of the data reconstruction which include how the various calibration constants are applied.

• Q.F. Zhou, J.E. Chen, Z.Y. Guo, Y.R. Lu, S.X. Peng, J. Zhao
  PKU/IHIP, Beijing

A compact remote control system with the SIMATIC S7-300 PLC is being designed for Peking University Neutron Imaging FaciliTY (PKUNIFTY). PKUNIFTY consists of a 2.45GHz ECR Deuteron ion source, LEBT, a 201.5MHz RFQ cavity, HEBT and Be target. Now PLC control system for ECR ion source and LEBT has been completed and tested. This paper will present the structure of the control system, the HMI with useful data recording system, and some measures took to improve the system safety.

• L.R. Shen, D.K. Liu
  SINAP, Shanghai

SSRF control system is a hierarchical standard accelerator control system based on EPICS. The VME 64X system, special embedded controller and PLCs are used for low level devices control or interlocks system. Using a uniform 1000Base-T backbone redundancy control network instead of field bus for mostly device controller with VLAN technique adopted, and integrate with EPICS using soft IOC. Digital technology such as digital power supply control system, new event timing system and digital phase control system are used and also integrated with some embedded EPICS IOC. An uniform System development and run time environment of hardware and software is adopted at the whole process. The high level physical application environment using MatLab 2007a with Accelerator Toolbox (AT) & middle layer with MatLab CA (Channel Access) connected component MCA/LabCA. The high level physical application can be integrated with the control system easily and conveniently. With the SSRF centre database, an enhanced distributed archive engine based on RDBS with native XML data type is been testing.

• Y.B. Yan, Y.B. Leng
  SINAP, Shanghai

Soft IOC is an ideal solution for high level global application of accelerator control and beam diagnostics due to easy online modification and rebooting. SSRF beam diagnostics system employees two soft IOCs to handle global tasks such as BPMs group access, orbit performance analyze and online data reliability analyze, which are hardly performed in bottom level IOC side and OPI side. This paper introduces the current status and future upgrade plan.

• G. Janša, I. Križnar, G. Pajor, I. Verstovšek
  Cosylab, Ljubljana
• R. Bär, L. Hechler, U. Krause
  GSI, Darmstadt

Present GSI control system uses an in-house developed CORBA based middleware called IFC. For FAIR project that will be build on the GSI site, a new control system is foreseen. New devices that are being integrated into the control system preferably will be developed in FESA. In this article, an IFC to FESA gateway will be presented. The gateway provides an intermediate layer that is able to talk to FESA device servers on one side and provide their functionality to existing IFC clients. The gateway will allow coexistence of FESA front-end implementations and existing GSI device servers, providing a smooth transition path to the future FAIR front-end environment. New GSI and FAIR devices that will be implemented in FESA will have to match GSI standards for nomenclature and device modeling. Exact match of new devices is not possible due to different hardware and software architecture of the new system, therefore a gateway solution is required. The gateway can translate the complete device model, including conversion from FESA to GSI data types. In the process of gateway design and implementation, valuable input was collected for the design of the future FAIR control system.

• M. Eguiraun
  ESS-Bilbao, Zamudio
• I. Arredondo
  ESS Bilbao, Bilbao
• I. Badillo, J. Jugo
  University of the Basque Country, Faculty of Science and Technology, Bilbao

The use of distributed control systems for improving control system's performance is a hot research topic. Thus, the importance of developing control systems across networked environment is rising, a lot of research is focused on developing middleware based solutions. On the other hand, EPICS is an extended control system middleware, which is based on TCP/UDP protocol. This protocol has non-deterministic characteristics, limiting its use for networked control systems. Despite of these characteristics, the interest on TCP based networks in industrial field has been increasing due to its advantages in cost and easy integration. In this work, EPICS as a networked control system is analyzed in order to develop strategies to improve its performance. For this purpose, an EPICS based networked control scheme is presented, where control loop is closed over the net. As opposed to usual way of working with EPICS, two IOCs are used located in different hosts. The first one performs data acquisition, while the second one calculates the control signal. The analysis and control performance study of such scheme is presented by using periodic sampling, as well as event based sampling approach.

• H. Damerau, S. Hancock, M. Schokker
  CERN, Geneva

To cope with the large variety of different beams for the LHC, the RF beam control in the CERN PS has evolved continuously to improve its flexibility and reliability. Single-bunch beams, several different multi-bunch beams with 25, 50 or 75 ns bunch spacing at ejection for LHC filling, as well as two lead-ion beam variants are now regularly produced in pulse-to-pulse operation. The multi-bunch beam control for protons can be easily re-adjusted from 0.25·10¹¹ to 1.3·10¹¹ particles per ejected bunch. Depending on the number of bunches injected from the PS Booster, the length of the ejected bunch train may vary from 8 to 72 bunches. This paper summarizes recent improvements in the low-level RF systems and gives an outlook on the future consolidation.

• Y.K. Chen, J. Chen, Y.-S. Cheng, P.C. Chiu, K.T. Hsu, K.H. Hu, C.H. Kuo, C.Y. Wu
  NSRRC, Hsinchu

Modbus-TCP is a widely used in industry for a long time and accelerator control system recently. Modbus protocol over Ethernet has advantages for non real-time applications due to its maturity. The TPS (Taiwan Photon Source) project will have many Modbus-TCP enable devices which distributed in utility system and accelerator system. The accelerator control environment of TPS project is an EPICS toolkit based system. Modbus-TCP might adopt for some subsystems. There are several possible Modbus-TCP devices including the prototype power supply for magnet field mapping application equip with Modbus-TCP interface, vacuum system local controller, front-end controller, and some monitoring devices. In this paper, we will summarise preparation efforts to accommodate the Modbus-TCP support in the TPS control system.

• Y.-S. Cheng, J. Chen, Y.K. Chen, K.T. Hsu, K.H. Hu, C.H. Kuo, C.Y. Wu
  NSRRC, Hsinchu

To enhance waveform and spectrum remote access supports in the Taiwan Light Source (TLS), development of the EPICS support of Ethernet-based oscilloscope and spectrum analyzer for the TLS is under way. The EPICS platforms which built to interface these instruments could access the waveform and spectrum through the PV (Process Variable) channel access. By using remote operations of waveform and spectrum acquisition, long distance cabling could be eliminated and signal quality be improved. The EDM (Extensible Display Manager) tool is used to implement the operation interface of control console and provide waveform display. According to specific purpose use, different graphical user interfaces to integrate waveform and spectrum acquisition are built. This project is the preparation for future control room integration with the Taiwan Photon Source control room. The efforts will be described at this report.

• K.T. Hsu, Y.-T. Chang, J. Chen, Y.K. Chen, Y.-S. Cheng, P.C. Chiu, S.Y. Hsu, K.H. Hu, C.H. Kuo, D. Lee, Y.R. Pan, C.-J. Wang, C.Y. Wu
  NSRRC, Hsinchu

Implementation of the Control system for the Taiwan Photon Source (TPS) is on going. The TPS control system will provide versatile environments for machine commissioning, operation, and to do accelerator experiments. The control system is based on EPICS toolkits. Test-bed has set up for various developments. The open architecture will facilitate machine upgrade, modification easily and minimize efforts for machine maintenance. Performance and reliability of the control system will be guaranteed from the design phase. Development status will be summary in this report.

• P.C. Chiu, J. Chen, Y.K. Chen, Y.-S. Cheng, K.T. Hsu, C.H. Kuo, C.Y. Wu
  NSRRC, Hsinchu

In order to help early development of TPS control system and user interface, a virtual accelerator model is constructed. The virtual accelerator has been created by AT toolbox and simulated beam behavior; the Middle Layer providing high level accelerator application is also used. LabCA interfaces between Matlab and EPICS (Experimental Physics and Industrial Control System). Such a system could speed development of commissioning required software and examine the correction of all procedures.

• C.Y. Wu, J. Chen, Y.-S. Cheng, C.-S. Fann, K.T. Hsu, S.Y. Hsu, K.H. Hu, C.H. Kuo, D. Lee, K.-K. Lin
  NSRRC, Hsinchu
• K. Furukawa, J.-I. Odagiri
  KEK, Ibaraki

The EPICS embedded programmable logic controller (PLC) has been developed based on F3RP61-2L, a CPU module of a FA-M3R series PLC running Linux OS. The EPICS IOC resided in F3RP61-2L module can access the registers of sequence CPU modules and I/O modules of the PLC. The embedded EPICS PLC was applied to control the prototype of pulse magnet power supply and support functionality testing remotely. The system comprises various input/output modules and a CPU module with built-in Ethernet interface. The control information (status of the power supply, ON, OFF, warn up, reset, read/write voltage, etc.) can be accessed remotely using EPICS client tools. The EDM is selected to develop the GUI for itself. Efforts are summarized in this report.

• C.M. Gulliford, I.V. Bazarov, J. Dobbins, R.M. Talman
  CLASSE, Ithaca, New York
• N. Malitsky
  BNL, Upton, Long Island, New York

Commissioning of the high brightness photoinjector for the Energy Recovery Linac at Cornell University continues. To aid in this process we have developed a 'Virtual Accelerator' application, which provides the beam physicist with an online high-level physics description of the machine. This application combines a linear optics model called Numerical Transfer Matrix (NTMAT), developed at Cornell, and EPICS-DDS, a middle-layer software based on the Experimental Physics and Industrial Control System (EPICS) toolkit and the Data Distribution Service (DDS) data-centric publish/subscribe model. We present the initial results of implementing this new software tool and its deployment in the Cornell ERL injector control room.

• G.B. Shen
  BNL, Upton, Long Island, New York
• P. Chu, J. Wu
  SLAC, Menlo Park, California
• M.R. Kraimer
  ANL, Argonne

A modular environment for beam commissioning and operation is under development, which is based on the client/server model. The service oriented architecture consists of a server for each supported service. At NSLS-II, a so-called "virtual accelerator" has been developed, which wraps simulator engines such as Tracy and Elegant onto an EPICS system. However, with the current solution, access to data is not flexible. We are designing a new online simulator server using structured data to provide a flexible method for accessing the simulation data. This paper describes recent results of the simulator server development.

• G.B. Shen, L. Yang
  BNL, Upton, Long Island, New York
• M.R. Kraimer
  ANL, Argonne

A fundamental infrastructure of software framework for beam commissioning for NSLS-II storage ring is in development. It adopts client/server model, and consists of various servers for data communication and management. Based on this structure, some physics applications are developed to satisfy the requirements of day-1 beam commissioning. This paper describes our status of infrastructure development and its applications.

• D.J. Peake, R.P. Rassool
  Melbourne
• M.J. Boland, R.T. Dowd, Y.E. Tan
  ASCo, Clayton, Victoria

The Australian Synchrotron storage ring has a resistive wall instability in the vertical plane. Presently this instability is being controlled by increasing the vertical chromaticity. However new in-vacuum insertion devices that significantly increase the ring impedance may demand chromatic corrections beyond the capabilities of the sextupole magnets. A transverse bunch-by-bunch feedback system has been commissioned to combat the vertical instability* and provide beam diagnostics**. A high frequency narrow band mode that could not be damped was initial encountered with IVUs at minimum gap preventing the system from being implemented during user beam. Tuning of the bunch fill pattern, the digital filters and mapping out the system response lead to a configuration for user mode operations.

* Spencer, M.J. et. al. EPAC'08, Genoa, Italy
** Peake, D.J. et. al. PAC'09, Vancouver, Cananda

• R. Nagaoka, L. Cassinari, M.D. Diop, M.-P. Level, C. Mariette, R. Sreedharan
  SOLEIL, Gif-sur-Yvette
• T. Nakamura
  JASRI/SPring-8, Hyogo-ken

In this paper we introduce and discuss the recent developments made in our digital transverse bunch by bunch feedback system at SOLEIL, which is routinely in service since the first user operation in both the high average current and high bunch current modes. The above includes installation of a third chain with a dedicated 4-electrode stripline intended to operate in the horizontal plane, an attempt to sample the BPM signal directly at the RF frequency without down-converting to the baseband following the success at SPring-8, a refined tuning procedure by measuring the feedback damping times as a function of the band frequency, as well as exploration of different digital filters ensuring a larger working range in terms of betatron tunes or a faster response against single bunch instabilities. The achieved performance and results are described. The observed evolution of the machine impedance and instabilities shall also be presented.

• R. Müller, B. Franksen, R. Görgen, R. Lange, I. Müller, J. Rahn, T. Schneegans
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
• P. Kuske
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin

In view of increased processing bandwidth at demanding experiments and the need for rapid compensation of noise spikes and new, yet unknown excitations a fast orbit feedback aiming at noise suppression in the 1Hz-50Hz range has become mandatory for the 3rd generation light source BESSY II. As a first step the fast setpoint transmission plus the replacement of all corrector power supplies is foreseen. Later - in combination with top-up operation - orbit stability can be further improved by replacing today's multiplexed analog beam position monitors by parallel processing fast digital units. This paper describes how the pilot installation of a small subset of fast corrector power supplies already allows to tune performance and study the benefits for today's most sensible experiments.

• P. Hartmann, S. Khan, D. Schirmer, G. Schünemann, P. Towalski, T. Weis
  DELTA, Dortmund

A stable beam orbit is essential for safe operation of particle accelerators. This applies to electron machines and even more to hadron machines running high beam currents. Based on developments at DELTA, basic designs of fast orbit feedbacks systems for the FAIR rings SIS18 and HESR (planned) and COSY at the Forschungszentrum Jülich are presented.

• S. Khan, J. Fürsch, P. Hartmann, T. Weis
  DELTA, Dortmund
• D. Teytelman
  Dimtel, San Jose

DELTA is a 1.5-GeV synchrotron radiation source at the TU Dortmund University with 2 ns bunch spacing. At nominal operating currents, the beam exhibits significant longitudinal centroid motion due to coupled-bunch instabilities. Two techniques were successfully used at DELTA to damp such instabilities: RF phase modulation, which also improves the beam lifetime, and bunch-by-bunch feedback. Using diagnostic data from the bunch-by-bunch feedback system, modal spectra and growth rates of the longitudinal instabilities were characterized. We also present a preliminary characterization of transverse coupled-bunch oscillations observed at the highest beam currents.

• M. Lonza, S. Cleva, S. Di Mitri, O. Ferrando, G. Gaio, A.A. Lutman, G. Penco, L. Pivetta, G. Scalamera
  ELETTRA, Basovizza

FERMI@Elettra is a new 4th-generation light source based on a single pass free electron laser. It consists of a 1.5-GeV normal-conducting linac working at 50 Hz repetition rate and two chains of undulators where the photon beams are produced with a seeded laser multistage mechanism. A number of control loops, some of them working on a shot by shot basis, are required to stabilize the crucial parameters of the beams. For this purpose, a generalized real-time framework integrated in the control system has been designed to flexibly and easily implement feedback loops using several monitoring and control variables. The paper discusses the requirements of the control loops and the implementation of the feedback framework. The first closed loop results and the experience gained in the operation of the feedbacks during the first phase of the machine commissioning will also be presented.

• A. Drago, M.M. Beretta
  INFN/LNF, Frascati (Roma)
• K.J. Bertsche, A. Novokhatski
  SLAC, Menlo Park, California
• M. Migliorati
  Rome University La Sapienza, Roma

The SuperB project has the goal to build in the Frascati or Tor Vergata area, an asymmetric e+/e^- Super Flavor Factory to achieve a peak luminosity > 10³⁶ cm^-2 s^-1. The SuperB design is based on collisions with extremely low vertical emittance beams. A source of emittance growth comes from the bunch by bunch feedback systems producing high power correction signals to damp the beams. To limit any undesirable effect, a large R&D program is in progress, partially funded by the INFN Fifth National Scientific Committee through the SFEED (SuperB feedback) project approved within the 2010 budget. One of the first steps of the R&D program consists in the upgrade and test of new 12-bit feedback systems in the vertical plane of the DAΦNE main rings. The systems are the direct evolution of the previous 8-bit system design by a KEK/SLAC/LNF collaboration, yielding a good compatibility with the powerful diagnostics and analysis programs developed in the past. Studies on their effects in the longitudinal plane are also in progress.

• F. Marcellini, D. Alesini, A. Ghigo
  INFN/LNF, Frascati (Roma)
• A. Andersson, I. Syratchev
  CERN, Geneva

In the two beam acceleration scheme the Main Beam must be precisely synchronized with respect to the RF power produced by the Drive Beam. Timing errors would have an impact on the collider performances. The Drive Beam phase errors should be controlled, by means of a feed forward system, within 0.1° (23fs @ 12GHz) to avoid a luminosity reduction larger than 2%. A beam phase arrival monitor is an essential component of the system. Its design has been based on the following main requirements: resolution of the order of 20fs, very low coupling impedance due to the very high beam current and integrated filtering elements to reject RF noise and weak fields in the beam pipe that could otherwise affect the measurements.

• M. Tobiyama, Y.H. Chin, Y. Kurimoto, T. Obina, M. Tejima, T. Toyama
  KEK, Ibaraki
• Y. Shobuda
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

Transverse bunch by bunch feedback systems for J-PARC MR accelerator has been designed and tested. Bunch positions are detected by Log-ratio position detection systems with center frequency of 12 MHz. The digital filter which consists of two LLRF4 boards samples the position signal with 64 times of RF frequency. Up to four sets of 16 tap FIR filter with one-turn delay and digital shift gain can be used. Preliminary results of beam test of the system are also shown.

• S. Onuma, K. Mochiki
  Tokyo City University, Tokyo
• T. Adachi, A. Kiyomichi, R. Muto, H. Nakagawa, H. Someya, M. Tomizawa
  KEK, Ibaraki
• T. Kimura
  Miyazaki University, Miyazaki
• K. Noda
  NIRS, Chiba-shi
• H. Sato
  Tsukuba University, Ibaraki

J-PARC is a new accelerator facility to produce MW-class high power proton beams. From the main ring (MR) high energy protons are extracted in a slow extracted mode for hadron experiments. The beam is required with as small ripple as possible to prevent pileup events in particle detectors or data acquisition systems. We took beam tests at HIMAC using a prototype signal processing unit. In these beam tests we had recognized the improvement of the extracted beam structure by using the feedback algorithm whose parameters were changed according to the beam characteristics. We have developed a new signal processing unit for the spill feedback control of J-PARC. The unit consists of three signal input ports (gate, spill intensity and residual beam intensity), three signal output ports (spill control magnets), two DSPs (power spectrum analysis and spill feedback control), dual port memories, FPGAs and a LAN interface (remote control with SUZAKU-EPICS). From October 2009, this unit is being used in the beam study of J-PARC MR to check the performance of digital filtering, phase-shift processing, servo feedback control, real-time power spectrum analysis and adoptive control.

• J. Resta-López, R. Apsimon, P. Burrows, G.B. Christian, B. Constance
  JAI, Oxford
• J. Alabau-Gonzalvo
  IFIC, Valencia

The commissioning of the ATF2 final focus test beam line facility is currently progressing towards the achievement of its first goal: to demonstrate a transverse beam size of about 40 nm at the focal point. In parallel, studies and R&D activities have already started towards the second goal of ATF2, which is the demonstration of nanometer level beam orbit stabilization. These two goals are important to achieve the luminosity required at future linear colliders. Beam-based intra-train feedback systems will play a crucial role in the stabilization of multi-bunch trains at such facilities. In this paper we present the design and simulation results of beam-based intra-train feedback systems at the ATF2: one system located in the extraction line at the entrance to the final focus, and another at the interaction point. The requirements and limitations of these systems are also discussed.

• J. Pfingstner, D. Schulte
  CERN, Geneva
• M. Hofbaur
  UMIT, Hall in Tirol

One of the major challenges of the CLIC main linac is the preservation of the ultra-low beam emittance. The dynamic effect of ground motion would lead to a rapid emittance increase. Orbit feedback systems (FB) have to be optimized to efficiently attenuate ground motion (disturbance), in spite of drifts of accelerator parameters (imperfect system knowledge). This paper presents a new FB strategy for the main linac of CLIC. It addresses the above mentioned issues, with the help of an adaptive control scheme. The first part of this system is a system identification unit. It delivers an estimate of the time-varying system behavior. The second part is a control algorithm, which uses the most recent system estimate of the identification unit. It uses H2 control theory to deliver an optimal prediction of the ground motion. This approach takes into account the frequency and spacial properties of the ground motion, as well as their impact on the emittance growth.

• R.J. Steinhagen, A. Boccardi, A.C. Butterworth, E. Calvo Giraldo, R. Denz, M. Gasior, J.L. Gonzalez, S. Jackson, L.K. Jensen, O.R. Jones, Q. King, G. Kruk, M. Lamont, S.T. Page, J. Wenninger
  CERN, Geneva

The LHC deploys a comprehensive suite of beam-based feedbacks for safe and reliable machine operation. This contribution summarises the commissioning and early results of the LHC feedback control systems on orbit, tune, chromaticity, and energy. Their performance – strongly linked to the associated beam instrumentation, external beam perturbation sources and optics uncertainties – is evaluated and compared with the feedback design assumptions.

• S. Aumon
  EPFL, Lausanne
• S. Aumon, H. Damerau, S.S. Gilardoni
  CERN, Geneva

A part of the beam losses at transition crossing of high intensity beams in the CERN PS have been attributed to an excursion of the closed orbit. The orbit jump occurs simultaneously with the jump of the transition energy triggered by pulsed quadrupoles. Investigations showed that the position of the pickups used for the radial loop system was not optimized with respect to the dispersion change caused by the fast change of the transition energy. Thanks to new electronics of the orbit measurement system, turn-by-turn orbit data could be recorded around transition crossing. Their analysis, together with calculations of the transverse optics, allowed determining a new choice of pickup positions for the radial loop. In comparison to the previous pickup configuration, the new configuration improves the mean radial position not only during transition crossing, but all along the acceleration cycle.

• C.H. Kuo, J. Chen, P.C. Chiu, K.T. Hsu, K.H. Hu
  NSRRC, Hsinchu

As the latest generation light source, TPS (Taiwan Photon Source) has stringent requirements to perform submicron beam stability with low emittance. The slow and fast correctors of integrated orbit feedback system have been designed for TPS project, therefore some feedback system designed based on them an operation experiences from TLS. This report will present performance simulation and the initial design of system infrastructure for large scale calculation and wide bandwidth communication. To perform this requirement, FPGA-based platform will be implemented to achieve low latency and fast computation. Some studies of integrated feedback loop, communication structure, devices control such as BPM electronics and corrector power supplies are also described.

• P. Burrows, R. Apsimon, D.R. Bett, G.B. Christian, B. Constance, H. Dabiri Khah, C. Perry, J. Resta-López, C. Swinson
  JAI, Oxford

We present the design and beam test results of a prototype beam-based digital feedback system for the Interaction Point of the International Linear Collider. A custom analogue front-end signal processor, FPGA-based digital signal processing boards, and kicker drive amplifier have been designed, built, deployed and tested with beam in the extraction line of the KEK Accelerator Test Facility (ATF2). The system was used to provide orbit correction to the train of bunches extracted from the ATF damping ring. The latency was measured to be approximately 140 ns.

• J. Resta-López, P. Burrows
  JAI, Oxford

The design luminosity of the future linear colliders requires transverse beam size at the nanometre level at the interaction point (IP), as well as stabilisation of the beams at the sub-nanometre level. Different imperfections, for example ground motion, can generate relative vertical offsets of the two colliding beams at the IP which significantly degrade the luminosity. In principle, a beam-based intra-train feedback system in the interaction region can correct the relative beam-beam offset and steer the beams back into collision. In addition, this feedback system might considerably help to relax the required tight stability tolerances of the final doublet magnets. For CLIC, with bunch separations of 0.5 ns and train length of 156 ns intra-train feedback corrections are specially challenging. In this paper we describe the design and simulation of an intra-train feedback system for CLIC. Results of luminosity performance simulation are presented and discussed.

• J. Resta-López
  JAI, Oxford
• D. Angal-Kalinin, J.-L. Fernandez-Hernando, F. Jackson
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• B. Dalena, D. Schulte, R. Tomás
  CERN, Geneva
• A. Seryi
  SLAC, Menlo Park, California

Important efforts have recently been dedicated to the improvement of the design of the baseline collimation system of the Compact Linear Collider (CLIC). Different aspects of the design have been optimized: the transverse collimation depths have been recalculated in order to reduce the collimator wakefield effects while maintaining a good efficiency in cleaning the undesired beam halo; the geometric design of the spoilers have also been reviewed to minimize wakefields; in addition, the optics design have been polished to improve the collimation efficiency. This paper describes the current status of the CLIC collimation system after this optimization.

• C. Bloomer, G. Rehm, C.A. Thomas
  Diamond, Oxfordshire

We present our observations of the medium term and long term stability of the photon beams at Diamond Light Source. Drift of the Electron Beam Position Monitors results in real X-ray beam movements, observed by both Front End X-ray Beam Position Monitors and beamline scintillator screens on some beamlines. We discuss how we are using these diagnostics tools to measure and characterise the drift. Medium term movements related to top-up cycles are seen, believed to be caused by changes to single bunch charge, and the long term drift of the electron beam position over several days and weeks is examined. A slow feedback system using X-ray Beam Position Monitors has been shown to successfully correct this drift. The results of these trials are presented.

• S. Xu, R. Laird, F. Lenkszus, H. Shang, C. Yao
  ANL, Argonne

The Advanced Photon Source (APS) real-time orbit feedback system is complex and faults are difficult to diagnose. This paper presents a diagnostic method based on fault tree analysis (FTA). The fault tree is created based on more than ten years operating experience of the system. The method is described to analyze the fault tree. The operator interface to the diagnostic tool is discussed.

• C. Yao, N.P. Di Monte, V. Sajaev
  ANL, Argonne

A bunch-by-bunch feedback system was installed at the APS in 2008. Close-loop tests were conducted and improvements have been made to the system that include two 500-watt amplifiers, a new location for the horizontal drive stripline, a two-blade new horizontal stripline, and upgrade of front-end electronics. With these improvements we are able to stabilize beam with a reduced chromaticity of 0.45 in the horizontal plane and 2.5 in the vertical plane for the 24-singlet bunch pattern. Beam lifetime has increased from 8.5 hours to 15 hours. We did not observe any obvious increase in the effective beam emittance and rms beam motion. More studies will be performed to explore the potential of improving beam performance of the hybrids fill pattern, which has a 16-mA leading bunch. We report the system improvements and the results of our test results.

cyao@aps.anl.gov

• J.D. Fox, A. Bullitt, T. Mastorides, G. Ndabashimiye, C.H. Rivetta, O. Turgut, D. Van Winkle
  SLAC, Menlo Park, California
• J.M. Byrd, M.A. Furman, J.-L. Vay
  LBNL, Berkeley, California
• R. De Maria
  BNL, Upton, Long Island, New York
• W. Höfle, G. Rumolo
  CERN, Geneva

The SPS at high intensities exhibits transverse single-bunch instabilities with signatures consistent with an Ecloud driven instability. We present recent MD data from the SPS, details of the instrument technique and spectral analysis methods which help reveal complex vertical motion that develops within a subset of the injected bunch trains. The beam motion is detected via wide-band exponential taper striplines and delta-σ hybrids. The raw sum and difference data is sampled at 50 GHz with 1.8 GHz bandwidth. Sliding window FFT techniques and RMS motion techniques show the development of large vertical tune shifts on portions of the bunch of nearly 0.025 from the base tune of 0.185. Results are presented via spectrograms and rms bunch slice trajectories to illustrate development of the unstable beam and time scale of development along the injected bunch train. The study shows that the growing unstable motion occupies a very broad frequency band of 1.2 GHz. These measurements are compared to numerical simulation results, and the system parameter implications for an Ecloud feedback system are outlined.

• R.A. Hardin
  ORNL RAD, Oak Ridge, Tennessee
• V.V. Danilov, C. Deibele
  ORNL, Oak Ridge, Tennessee

The prototype of an analog transverse (vertical and horizontal) feedback system to actively damp the electron-proton (e-p) instability has been developed and tested on the ORNL Spallation Neutron Source (SNS). We will describe the principle components, system configuration, and review several experimental studies geared towards understanding the current performance and limitations of the system.

• R. De Maria
  BNL, Upton, Long Island, New York
• C. Boccard, W. Höfle, G. Kotzian, C. Palau Montava, B. Salvant
  CERN, Geneva

The SPS exponential coupler stripline are used to study single bunch instabilities. An accurate description of the response of the pickup is required to obtain high resolution measurements of the bunch vertical motion along the longitudinal axis. In this study we present the results of the comparison between dedicated beam experiments and electromagnetic simulations of a geometrical model of the stripline.

• T. Kume, K. Furukawa, M. Satoh, T. Suwada
  KEK, Ibaraki
• E. Okuyama
  Akita University, Akita

Profile shape measurements detecting profile slope angle, which corresponds to the differential of the profile shape, have been used for evaluating profile shapes highly precisely. They are hardly affected by scanning error in measurement and considered to have advantages for long distance measurements. Here, profile measurement using a level was adopted for straightness alignment of the KEK e-/e⁺ injector linac, considering the straightness alignment as a profile shape measurement. The slope angles between the alignment base plates of the linac could be detected with reproducibility of 10 micro-rad (σ) by sequential measurement interval of 1 to 2 m. The reproducibility of the straightness derived from the angle measurements was 42 micrometer (σ) for 69 m of the measurement distance and agreed well with the estimated value based on our error propagation model. These results show that straightness reproducibility of better than 1 mm (2-σ) can be achieved for 500 m of the KEK e-/e⁺ injector linac by sampling interval of 2m, and for 10 km of the ILC linac by sampling interval of 20 cm.

• M. Satoh, E. Kadokura, T. Suwada
  KEK, Ibaraki

A new laser-based alignment system is under development in order to precisely align accelerator components along an ideal straight line at the KEKB injector linac. The new alignment system is strongly required in order to stably accelerate high-brightness electron and positron beams with high bunch charges and also to keep the beam stability with higher quality towards the next generation of B-factories. A new laser optics with Airy pattern (so-called Airy beam) has been developed and the laser propagation characteristics in vacuum has been systematically investigated at a 82-m-long straight section of a beam line of the injector linac. The laser-based alignment measurement based on the new laser optics has been carried out with a measurement resolution of ±0.1 mm level by using a previously-used laser detection system. The experimental results are reported along with the basic design of the new laser-based alignment system.

• T. Suwada, M. Satoh
  KEK, Ibaraki

A new laser-based alignment system is under development at the KEKB injector linac. We are revisiting our alignment system because the previous alignment system has become obsolete. The new alignment system is again required to increase the stability of the electron- and positron-beam injection towards next-generation of B-factories. It is similar to the previous one, which comprises a laser-diode system and quadrant photodetectors installed in vacuum light pipes. A displacement of a girder unit of the accelerating structure can be precisely measured in the direction of the laser-ray trace, where the laser light must stably propagate up to 500-m-long downstream without any orbital and beam-size fluctuation. A novel approach in which a two-beam-interference laser-light propagates in the vacuum light pipe, has been designed to increase the alignment precision based on the quadrant photodetector measurement. The propagating laser spot sizes can be narrowed due to the two-beam interference over the Rayleigh-range limit. The design of the new laser-based alignment system is summarized along with some experimental results in this report.

• K. Artoos, C.G.R.L. Collette, P. Fernandez Carmona, M. Guinchard, C. Hauviller, S.M. Janssens, A.M. Kuzmin, A. Slaathaug, M.V. Sylte
  CERN, Geneva

A prerequisite for a successful nanometre level magnet stabilization and pointing system is a low background vibration level. This paper will summarize and compare the ground motion measurements made recently in different accelerator environments at e.g. CERN, CESRTA and PSI. Furthermore the paper will give the beginning of an inventory and characterization of some technical noise sources, and their propagation and influence in an accelerator environment. The importance of the magnet support is also mentioned. Finally, some advances in the characterization of the nanometre vibration measurement techniques will be given.

• M. Kago, T. Matsushita, N. Nariyama, C. Saji, R. Tanaka, A. Yamashita
  JASRI/SPring-8, Hyogo-ken
• Y. Asano, T. Fukui, T. Itoga
  RIKEN/SPring-8, Hyogo

The accelerator safety interlock system (ASIS) for the XFEL/SPring-8 protects personnel from radiation hazard. We designed the ASIS consisting of three independent systems; a central interlock system, an emergency interlock system and a beam route interlock system. The central interlock system monitors the machine tunnel security, status of beam line interlock system and radiation monitoring system. The emergency interlock system monitors status of emergency stop buttons. The beam route interlock system monitors electron beam route by inputting the current of the bending magnets at the electron-beam switching points. If any system trips, or if any system detects unsafe status, the permission signal for the accelerator operation from the system is off and the electron beam is inhibited. In addition, it is demanded that the permission signals must be transmitted within 16.6 ms. Therefore, the stability and fast response are required for the XFEL safety interlock system. We adopted programmable logic controllers (PLC) for the stability, and developed optical modules for the fast signal transmission. This paper describes system design of the ASIS.

• X.-M. Maréchal
  JASRI/SPring-8, Hyogo-ken
• Y. Asano, T. Itoga
  RIKEN/SPring-8, Hyogo

Fiber-based beam loss monitors (BLM) have attracted much attention in recent years. Among them, systems using the detection of the Cerenkov light generated by the secondary charged particles hitting an optical fiber set along the vacuum chamber, offer the possibility to detect beam losses with a very fast response time (less than a few ms) over long distances, good position accuracy and sensitivity at a reasonable cost. For the undulator section of the SPring-8 X-FEL, radiation safety considerations set the desirable detection limit at 1 pC (corresponding to a 0.1% beam loss of the initial 1 nC/pulse) over more than a hundred meter. We report on a the test operation of a fiber-based BLM carried out at the 250 MeV SPring-8 Compact SASE Source (SCSS), a 1/16th model of the future X-FEL. The expected detection limit of the BLM based on a large (400 μm) core multimode fiber is below 2 pC over 120 m (for a corresponding 10 mV signal) while the position accuracy is expected to be better than one meter.

• T. Itoga, Y. Asano
  RIKEN/SPring-8, Hyogo
• X.-M. Maréchal
  JASRI/SPring-8, Hyogo-ken

A fiber-based beam loss monitors (BLM) is under development for the undulator section of the SPring-8 X-FEL: the system is based on the detection of the Cerenkov light generated by the secondary charged particles hitting an optical fiber set along the vacuum chamber. Various parameters come into account in the final performance of the system, such as the impact angle and energy of the lost electrons, the fiber position (angular and radial) with respect to the point of impact, fiber characteristics (numerical aperture, index, diameter), etc. Thorough numerical studies have been carried out to investigate the performances of the system. Comparison with the experimental results obtained at the SPring-8 Compact SASE Source (SCSS), a 1/16th model of the future X-FEL are also given.

• N. Nariyama, H. Aoyagi, M. Kago, T. Matsushita, C. Saji, R. Tanaka
  JASRI/SPring-8, Hyogo-ken
• Y. Asano, T. Itoga
  RIKEN/SPring-8, Hyogo

The accelerator safety interlock system of XFEL/SPring-8 was designed to fulfill the requirement of matching with the safety interlock system of SPring-8 because both safety systems are planning to be unified in near future to deal with the electron beam injection from XFEL to SPring-8. At XFEL, however, additional requirements for the system also existed; the designed radiation shielding requires when the electrons are not injected into the dump core properly, the beam has to be terminated within 16 msec, which corresponds to 60 Hz operation, to avoid the next bunch coming. An outline of such different design criteria is presented together with the concept of the safety interlock system. The radiation monitoring system, which was also the same as that of SPring-8, was installed by reinforcing the redundancy and response time. Gamma and neutron monitors are set at 14 positions near the assumed loss points in the accessible place of the controlled area. The dose equivalent data are sent to the radiation monitoring systems of XFEL and SPring-8, respectively, and when the measured dose exceeds the preset level, an alarm signal is sent to the safety interlock promptly.

• Y. Shimosaki, K. Kobayashi
  JASRI/SPring-8, Hyogo-ken

Electricity generation from scattered secondary particles has been examined for a kind of energy-recovery by using a beam loss monitor at the SPring-8 storage ring, in which PIN photodiodes are utilized without a reversed bias voltage in similar to a solar cell. The system and results will be reported.

• K. Yamamoto, H. Harada, S. Hatakeyama, N. Hayashi, H. Hotchi, P.K. Saha, M. Yoshimoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
• R. Saeki
  KEK/JAEA, Ibaraki-Ken

A 3GeV Rapid-Cycling Synchrotron (RCS) in Japan Proton Accelerator Research Complex (J-PARC) has continuously provided more than 100kW proton beam to the Neutron target since October 2009. And we also successfully accelerated 300kW beam for one hour on December 10th by way of trial. We found some problems through these experiences. We report those problems and the residual dose in such high intensity operation.

• I.I. Popova, P.D. Ferguson, F. X. Gallmeier, E. Iverson
  ORNL, Oak Ridge, Tennessee
• W. Lu
  ORNL RAD, Oak Ridge, Tennessee

All stages of the SNS development require significant research and development work in the field of radiological shielding design to assure safety from a radiation-protection point of view for facility operation and to optimize accelerator and target performance. Here we present an overview of on-going shielding work and associated with it procedures and regulations. In the present time, the most of the shielding work is focused on the neutron beam lines and their instrument enclosures in order to commission and provide save operation in the future. This effort is performed according to the guidelines for shielding calculations of SNS neutron beam lines, which sets standards for the analyses and helps to prepare for the Instrument Readiness Review (IRR). The IRR ascertains that the instruments has been design, constructed, and installed to allow safe operation and maintenance. In addition, there is still support for the accelerator facility to redesign parts of the accelerator structures, to design shielding for removed components and test stands for accelerator structures, and for radiation protection analyses for evaluations of accelerator and target safety systems.

• S.L. Kramer, W.R. Casey, P.K. Job
  BNL, Upton, Long Island, New York

The shielding design for the NSLS-II will provide adequate protection for the full injected beam loss in two periods of the ring around the injection point, but the remainder of the ring is shielded for lower losses of <10% full beam loss. This will require a system to insure that beam losses don't exceed these levels for a period of time that could cause levels outside the shield walls. This beam containment system will measure, provide a level of control and alarm indication of the beam power losses along the beam path from the source (e-gun, linac) thru the injection system and the storage ring. This system will consist of collimators that will provide limits to (an potentially measure) the beam miss-steering and control the loss points of the charge and monitors that will measure the average beam current losses along the beam path and alarm when this beam power loss exceeds the level set by the shielding specifications. This will require some new ideas in beam loss detection capability and collimation. The initial planning and R&D program will be presented.

• H. Aoyagi, T. Bizen, N. Nariyama
  JASRI/SPring-8, Hyogo-ken
• Y. Asano, T. Itoga, H. Kitamura, T. Tanaka
  RIKEN/SPring-8, Hyogo

A beam halo region of an electron beam at a linear accelerator might hit the undulator magnets and degrade undulator permanent magnets. An interlock sensor is indispensable to protect the magnets against radiation damage. We have been developing an electron beam halo monitor using diamond detectors for an interlock sensor at the X-ray free electron laser facility at SPring-8 (XFEL/SPring-8). The diamond detectors are operated in photoconductive mode. Pulse-by-pulse measurements are adopted to suppress the background noise efficiently. The feasibility tests of this monitor have been performed at the SPring-8 compact SASE source (SCSS) test accelerator for XFEL/SPring-8, and the results will be summarized.

• M. Sapinski, B. Dehning
  CERN, Geneva
• A. Priebe
  Poznań University of Technology, Poznań

The LHC beam loss measurement system is mainly used to trigger the beam abort in case a magnet coil quench level is approached. The predicted heat deposition in the superconducting coils of the magnets have been determined by particle shower simulation codes, while the liquid helium cooling capacity of the system has been both simulated and measured. The results have been combined to determine the abort thresholds. Measurements of the energy depositions of lost protons from the initial beams in the LHC are used to determine the accuracy of the beam abort threshold settings. The simulation predictions are reviewed and compared with the measurement results.

• C. Kurfuerst, B. Dehning, E.B. Holzer, A. Nordt, M. Sapinski
  CERN, Geneva

Particle losses in the LHC arcs are mainly expected in the interconnection region between a dipole and quadrupole magnet. The maximal beam size, the maximal orbit excursion and aperture changes cause the enhancement of losses at this location. Extensive Geant4 simulations have been performed to characterise this particular region to establish beam abort settings for the beam loss monitors in these areas. Data from first LHC beam loss measurements have been used to check and determine the most likely proton impact locations. This input has been used to optimise the simulations used for the definition of thresholds settings. The accuracy of these settings is investigated by comparing the simulations with actual loss measurements.

• M. Jonker, E.B. Holzer, S. Mallows, D. Manglunki, G. Morpurgo, Th. Otto, M. Sapinski, F. Tecker, J.A. Uythoven
  CERN, Geneva

The proposed Compact Linear Collider (CLIC) is based on a two-beam acceleration scheme. The energy of high intensity, low energy drive beams is extracted and transferred to low intensity, high energy main beams. Direct ionization loss by the beam particles is the principal damage mechanism. The total charge gives a single drive beam-train a damage potential that is two orders of magnitude above the level causing structural damage in copper. For the main beam, it is the extreme charge density due to the microscopic beam size that gives it a damage potential of four orders of magnitude above the safe level. The machine protection system has to cope with a wide variety of failures, from real time failures (RF breakdowns, kickers misfiring), to slow equipment failures, to beam instabilities (caused by e.g. temperature drifts, slow ground motions). This paper discusses the baseline for the CLIC machine protection system which is based on passive, active and permit based protection. As the permit based protection depends on the measured performance of the previous pulse, the bootstrap procedure with safe beams and stepwise increase in beam intensities, is also discussed.

• T. Lefèvre, S. Bart Pedersen, A. Boccardi, E. Bravin, A. Goldblatt, A. Jeff, F. Roncarolo
  CERN, Geneva
• A.S. Fisher
  SLAC, Menlo Park, California

The LHC beam dump system relies on extraction kickers that need 3 microseconds to rise up to their nominal field. As a consequence, particles crossing the kickers during this rise time will not be dumped properly. The proton population during this time should remain below quench and damage limits at all times. A specific monitor has been designed to measure the particle population in this gap. It is based on the detection of Synchrotron radiation using a gated photomultiplier. Since the quench and damage limits change with the beam energy, the acceptable population in the abort gap and the settings of the monitor must be adapted accordingly. This paper presents the design of the monitor, the calibration procedure and the detector performance with beam.

• B. Puccio, A. Castañeda, M. Kwiatkowski, I. Romera, B. Todd
  CERN, Geneva

A complex Machine Protection System has been designed to protect the LHC machine from an accidental release of the beam energy, with about 20 subsystems providing status information to the Beam Interlock System (BIS). Only if the subsystems are in the correct state for beam operation, the BIS receives a status flag and beam can be injected into LHC. The BIS also relays commands from the connected subsystems in case of failure for emergency extraction of beam to the LHC Beam Dump Block. To maintain the required level of safety of the BIS, the performance of the key components is verified before every fill of the machine and validated after every emergency beam dump before beam operation is allowed to continue. This includes all critical paths, starting from the inputs from connected system triggering a beam dump request, followed by the correct interruption and propagation sequence of the two redundant beam permit loops until the final extraction of the beam via the LHC beam dumping system. In this paper we report about the experience with the BIS that has been deployed for some years in the SPS (as LHC injector), in the transfer lines between SPS and LHC and recently in LHC.

• M. Sapinski, B. Dehning, E.B. Holzer, M. Jonker, S. Mallows, Th. Otto
  CERN, Geneva
• C.P. Welsch
  Cockcroft Institute, Warrington, Cheshire

The Compact Linear Collider (CLIC) is a proposed multi-TeV linear electron-positron collider being designed by a world-wide collaboration. It is based on a novel two-beam acceleration scheme in which two beams (drive and main beam) are placed in parallel to each other and energy is transferred from the drive beam to the main one. Beam losses on either of them can have catastrophic consequences for the machine because of high intensity (drive beam) or high energy and small emittance (main beam). In the framework of machine protection, a Beam Loss Monitoring system has to be put in place. This paper discusses the requirements for the beam loss system in terms of detector sensitivity, resolution, dynamic range and ability to distinguish losses originating from various sources. A particular attention is given to the two-beam module where the protection from beam losses is particularly challenging and important.

• S.T. Artikova
  MPI-K, Heidelberg
• R.B. Fiorito, A.G. Shkvarunets, H.D. Zhang
  UMD, College Park, Maryland
• C.P. Welsch
  Cockcroft Institute, Warrington, Cheshire

Beam halo can have severe effects on the performance of high energy accelerators. It reduces the experimental throughput, may lead to noise in the experiments, or even damaging of accelerator components. In order to understand and ideally control the formation and evolution of beam halo, detailed simulation studies are required. In this contribution halo generation mechanisms and the underlying physical principles are first presented, before the particular case of the CLIC Test Facility (CTF3) is discussed in detail. Analytical, numerical and simulation studies are combined to estimate the relevant sources of halo formation and to study halo propagation in the different CTF3 sections.

• S. Schulz, L.-G. Wißmann
  Uni HH, Hamburg
• V. R. Arsov
  PSI, Villigen
• M.K. Bock, M. Felber, P. Gessler, K.E. Hacker, F. Ludwig, H. Schlarb, B. Schmidt, J. Zemella
  DESY, Hamburg

After its upgrade, the free-electron laser in Hamburg (FLASH) will start operating with an exchanged RF-gun driven by an improved photoinjector laser. Since the SASE FEL process is very sensitive to the RF gun phase it is highly desirable to implement phase stabilization feedback, which, in turn, requires an arrival-time stabilization of the photoinjector laser pulses. In this paper we report on the synchronization of the photoinjector laser system to the optical timing reference using an optical cross-correlation scheme. This enables not only the measurement of the timing jitter, but also the stabilization using adaptive feed-forward algorithms acting on an EOM incorporated in the laser's pulse train oscillator. First results from the commissioning and future plans for a feedback system are discussed.

• G. Franzini, O. Coiro, D. Pellegrini, M. Serio, A. Stella
  INFN/LNF, Frascati (Roma)
• M. Pezzetta, M. Pullia
  CNAO Foundation, Milan

CNAO, the Italian Centre of Oncological Hadrontherapy located in Pavia, is under commissioning and will be soon fully operational. It is based on a synchrotron that can accelerate carbon ions up to 400 MeV/u and protons up to 250 MeV for the treatment of patients. In this paper we present the subsystem, called B-Train, which has the purpose of measuring the magnetic field in a dedicated dipole connected in series with the sixteen dipoles of the synchrotron and to provide instantaneous values of the synchrotron field to the dipole power supply, to the RF, diagnostics and dump bumpers control systems, via optical lines, using a custom communication protocol. In order to measure the magnetic field with the specified precision (0.1G over 1.5T @ 3 T/s), a different approach has been taken with respect to previous versions of the system. The field is obtained by digitizing the voltage induced on a pick-up coil inserted in the gap of the dedicated dipole through a 18 bit, 1.25 Msamples/s ADC and integrating it by numerical methods. This paper describes the final design and features of the B-Train system, as well as the results obtained on the magnetic field readings precision.

• J. Tratnik, B. Batagelj, L. Pavlovič, M. Vidmar
  University of Ljubljana, Faculty of Electrical Engineering, Ljubljana
• P.L. Lemut, V. Poucki
  I-Tech, Solkan

The new generation of accelerators requires timing distribution and RF synchronization with femtosecond precision in terms of jitter and long-term stability. The proposed electro-optical synchronization system makes use of commercial telecom single-mode optical fibre operating at 1550 nm.. It operates on over 300 m distance. It consists of a transmitter, located near a low-jitter master oscillator, and receiver, located at the remote location. The field experiments have been done in the accelerator environment with the fibre pair in the tunnel. The prototype units were installed at the same location to make phase difference measurement simple. Temperature in various installation points, phase difference and both units internal operational parameters were continuously monitored and stored. Data was post-analysed and conclusions were used for hardware changes and mostly the long-term stability improvement. A dedicated phase detector was designed to monitor less than 20 fs changes. Results are showing 80 fs RMS and 30 fs stability over 20 and 8 hours respectively. The prototype is being redesigned for manufacturing with some new features for improved long-term stability.