• A. Hofmann, I. Birkel, M. Fitterer, S. Hillenbrand, N. Hiller, E. Huttel, V. Judin, M. Klein, S. Marsching, A.-S. Müller, N.J. Smale, K.G. Sonnad, P.F. Tavares
  KIT, Karlsruhe

A new 90 kV e-gun had been installed at the 50 MeV microtron at ANKA. The emittance of the gun has been measured in long pulse mode (1 us, 200 mA) with a pepper-pot, resulting in 5 u.rad RMS normalised emittance. The single pulse width is less than 1 ns, resulting in a bunch purity in the storage ring of better 0.5 %. The old timing system for gun and injection elements based on 4 Stanford delay generator has now been replaced by an event driven system from Micro-Research Finland (MRF). This consists of one event generator and one event receiver. Visualisation and programming is achieved with PVSS from ETM Austria. The e-gun trigger can be adjusted in 10 ps steps. The entire system is phase locked to the 499.69 MHz RF signal.

• J.W. Flanagan, H. Fukuma, H. Ikeda, T.M. Mitsuhashi
  KEK, Ibaraki
• J.P. Alexander, N. Eggert, W.H. Hopkins, M.A. Palmer, D.P. Peterson
  CLASSE, Ithaca, New York
• B. Kreis
  Cornell University, Ithaca, New York
• G.S. Varner
  UH, Honolulu, HI

An x-ray beam size monitor based on coded aperture imaging* has been developed at CesrTA, for the purpose of making bunch-by-bunch, turn-by-turn measurements of low emittance beams. Using low-emittance beam (~44 pm, or 16 microns at the x-ray source point) we have been able to make detailed comparisons between the measured mask response and that predicted by theory, validating our simulations of the mask response. In turn, we demonstrate the ability to measure both integrated and single-bunch turn-by-turn beam sizes and positions for monitoring the progress of the low-emittance tuning of the machine, and for electron-cloud instability-related beam dynamics studies.

* J.W. Flanagan et al., EPAC08, 1029 (2008).

• Y.B. Leng, Y.B. Yan, L.Y. Yu, W.M. Zhou
  SSRF, Shanghai

Bunch charge uniformity control is very important for storage ring top-up operation. In order to monitor filling pattern and measure bunch charge precisely an PXI waveform digitizer based data acquisition system was developed to retrieve bunch charge information from BPM pickup signals. Effective sampling rate could be extended to 400GHz by waveform rebuilding technology, which folds multi turns data into single turn with real time sampling rate of 8GHz. Online evaluation shows charge resolution could be better than 0.5% for 1nC range.

• B. Keil, R. Baldinger, R. Ditter, R. Kramert, G. Marinkovic, P. Pollet, M. Roggli, M. Rohrer, V. Schlott, M. Stadler, D.M. Treyer
  PSI, Villigen
• W. Decking, D. Lipka, D. Nölle, M. Siemens, T. Traber, S. Vilcins
  DESY, Hamburg
• O. Napoly, C.S. Simon
  CEA, Gif-sur-Yvette
• J.-P. Prestel, N. Rouvière
  IPN, Orsay

The European XFEL is an X-ray free electron laser user facility that is currently being built in Hamburg by an international consortium. The electron BPM system of the XFEL is developed by a collaboration of PSI, DESY, and CEA/Saclay/Irfu. Cavity BPMs will be used in all parts of the E-XFEL where highest resolution and lowest drift is required, e.g. in the undulators and some locations in the beam transfer lines. In the cryostats of the superconducting 17.5GeV main linac, 2/3rds of the BPMs will be buttons, while 1/3rd will be re-entrant cavities that promise higher resolution than buttons at low bunch charges. The transfer lines will also be equipped with cost-efficient button BPMs. The BPM electronics is based on a modular system concept, with a common FPGA-based digital back-end design for all BPMs and pickup-specific analog RF front-ends. This paper introduces the design concepts and reports on the project status and measurement results of BPM pickup and electronics prototypes.

• Y. Susaki, K. Ohmi
  KEK, Ibaraki

Single bunch instability caused by electron cloud can depend on emittance, because the electron oscillation period in positron bunch is large. The single bunch instability should appear as a head-tail motion with synchro-beta frequency. We discuss the single bunch instability in low emittance rings, CesrTA, Super B factories and ILC damping ring with focusing the threshold and synchro-beta oscillation.

• A. Novokhatski, M.K. Sullivan
  SLAC, Menlo Park, California

We study the bunch field diffusion and energy dissipation in the beam pipe of the Super-B detector, which consists of two coaxial Be thin pipes (half a millimeter). Cooling water will run between these two pipes. Gold and nickel will be sputtered (several microns) onto the beryllium pipe. The Maxwell equations for the beam fields in these thin layers are solved numerically for the case of infinite pipes. We also calculate the amplitude of electromagnetic fields outside the beam pipe, which may be noticeable as the beam current can reach 4 A in each beam. Results of simulations are used for the design of this central part of the Super-B detector.

• M. Znidarcic
  I-Tech, Solkan
• K.B. Scheidt
  ESRF, Grenoble

Initially, the Libera Brilliance Single Pass was intended for beam position monitoring at injector system for the FEL machines, this was afterwards followed by the idea of using it on transfer lines on the 3rd generation light sources. The device can be used on pickup buttons and on striplines. The measurement principles and results of Libera Brilliance Single Pass at ESRF, as beam-charge monitor and injection-efficiency monitor, are presented.

• P. Jain
  Sokendai, Ibaraki
• H. Fukuma, K. Kanazawa, Y. Suetsugu
  KEK, Ibaraki

Electron Cloud (ECLOUD) deteriorates the performance of proton and positron storage rings. Therefore it is desirable to understand the ECLOUD buildup in a given machine. The data taken by Retarded Field Analyzer (RFA) with a multi channel plate showed that the signal had the peaks coinciding with the positron bunch pattern if a high voltage of -2kV is applied to the retarded grid*. This suggests that the cloud electrons get maximum kick near the positron bunch. A computer program has been developed to study the near bunch ECLOUD density at KEKB LER (Low Energy Ring). In simulations, secondary electron emission is modeled according to the Furman and Pivi's model**. In this paper we compare the simulation results of the ECLOUD buildup with the experiments performed in KEK under different beam-optics elements.

* K. Kanazawa et al., PAC05, 10⁵⁴.
** M. Furman and M. Pivi, PRST-AB, 5, 124404 (2002).

• P.F. Tavares
  Karlsruhe Institute of Technology (KIT), Karlsruhe
• M. Fitterer, N. Hiller, A. Hofmann, V. Judin, M. Klein, S. Marsching, N.J. Smale, K.G. Sonnad
  KIT, Karlsruhe
• E. Huttel, A.-S. Müller
  FZK, Karlsruhe
• P.F. Tavares
  LNLS, Campinas

We present results of a series of measurements aimed at characterizing the beam coupling impedances in the ANKA electron storage ring. The measurements include transverse coherent tune shifts, bunch lengthening and synchronous phase shift as a function of single bunch current. These were performed under a variety of conditions in the ANKA ring, including injection energy (500 MeV), nominal operating energy (2.5 GeV) as well as at 1.3 GeV and in the low alpha mode and are part of a longer term effort to understand the ANKA impedance over a wide frequency range.

• M.M. El-Ashmawy, G. D'Auria
  ELETTRA, Basovizza

In most of the Linac based 4th Generation Light Sources now under development (e.g. FERMI@ELETTRA [1]), a short accelerating structure operating at higher harmonics (i.e. X-band, 12 GHz), is adopted to linearize the beam's longitudinal phase space [2]. This structure could be either travelling wave (TW) or standing wave (SW) type. As it is well known, each one of such structures has its own advantages and drawbacks in terms of RF properties but there is a lack of information about the wake fields of each type compared to the other. In this paper an overall comparison, from the wakefields point of view, of two different X-band structures will be carried out. The purpose is to evaluate quantitatively the longitudinal and transverse wake functions of the structures, determining their relevant wake integrals, such as the average value of energy loss, rms energy spread, kick factor and kick spread.

• S. Aumon
  EPFL, Lausanne
• S. Aumon, M. Delrieux, P. Freyermuth, S.S. Gilardoni, E. Métral, G. Rumolo, B. Salvant, R.R. Steerenberg
  CERN, Geneva

Transition crossing in the CERN PS is critical for the stability of high intensity beams, even with the use of a second order gamma jump scheme. The intense single bunch beam used for the neutron Time-of-Flight facility (n-ToF) needs a controlled longitudinal emittance blowup at flat bottom to prevent a fast single-bunch vertical instability from developing near transition. This instability is believed to be of Transverse Mode Coupling (TMCI) type. A series of measurements taken throughout 2008 and 2009 aim at using this TMCI observed on the ToF beam at transition, as a tool for estimating the transverse global impedance of the PS. For this purpose, we compare the measurement results with the predictions of the HEADTAIL code and find the matching parameters. This procedure also allows a better understanding of the different mechanisms involved and can suggest how to improve the gamma jump scheme for a possible intensity upgrade of the n-ToF beam.

• J. Rowland, R.T. Fielder
  Diamond, Oxfordshire
• R. Bartolini
  JAI, Oxford
• R. Nagaoka
  SOLEIL, Gif-sur-Yvette

Within the common programme on the analysis of collective instabilities at Diamond and SOLEIL, the numerical codes mbtrack and sbtrack have been extended to include a full description of the nonlinearities in the storage rings by means of the nonlinear one-turn map. We present the details of the map implementation and the recent results on the analysis of the effects of the nonlinear terms of the map on the characteristics of the collective instabilities at the two machines.

• W. Liu, W.-H. Huang, C.-X. Tang, D. Wu
  TUB, Beijing

Smith-Purcell radiation (SPR) is emitted when an electron passes near the surface of a periodic metallic grating. The radiation wavelength λ observed at the angle θ measured from a direction of surface grating is determined by λ=D/|n|(1/β cosθ), Where D is the grating period, βc is the electron velocity, c is the speed of light, and the integer n is the spectral order. This radiation mechanism is widely applicated to THz radiation source, for which can be developed into tunable and compact one. In this paper, the radiation characteristics of terahertz (THz) SPR generated from the ultrashort electron beam are analyzed with the three-dimensional particle-in-cell simulation. For obtaining the intense THz radiation, the grating parameters and that of ultrashort electron beam are optimum. The radiation power and energy are obtained by the PIC simulation. The band width of train bunches is compared with that of single bunch. The formation factors including the longitudinal and transverse are calculated. Through this study, we observe that the radiation power is enhanced and the band width can be adjusted.

• L.O. Dallin, W.A. Wurtz
  CLS, Saskatoon, Saskatchewan

Preliminary observations of coherent synchrotron radiation (CSR) at the Canadian Light Source have been reported earlier. At that time a more suitable operating point was identified based on particle tracking calculations. These calculations showed that a large stable longitudinal phase space can be achieved through adjustment of the chromaticities. With the implementation of these operating conditions CSR has been produced with much improved beam lifetime. CSR has been produced both with multiple bunches at 1.5 GeV and with a single bunch at the nominal 2.9 GeV beam energy. The production of CSR with these new operating points has proven to be reliable and repeatable. Operations at the nominal beam energy allows for setup times of under 20 minutes. With a beam lifetime (1/e) of over 7 hours single shifts dedicated to CSR production are now practical.

• A.S. Setty, D. Jousse, J.-L. Pastre
  THALES, Colombes
• E. Weihreter
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin

A turn key 50 MeV linac is under construction, in order to inject electrons into the booster of BESSY II synchrotron in replacement of the existing microtron. The linac will deliver electrons according to two operations modes: a Short Pulse Mode (< 1 ns - 0.35 nC) and a Long Pulse Mode (40 to 300 ns - 3 nC). We have calculated the beam dynamics using our in house code, PRODYN *, from the gun to the end of the linac. This code has been previously used for the beam dynamics of the SOLEIL and ALBA linacs. The beam behaviour, such as the radial control, the bunching process, the energy spread and emittance are analysed.

* A.Setty, "Electrons RF auto-focusing and capture in bunchers", Linear Accelerator Conference 1988, Virginia.

• G. Wüstefeld, J. Feikes, M.V. Hartrott, M. Ries
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
• A. Hoehl, R. Klein, R. Müller, A. Serdyukov, G. Ulm
  PTB, Berlin

The Metrology Light Source* is the first storage ring optimized for THz generation**. It applies a bunch shortening mode, based on a flexible momentum compaction factor 'alpha'. The emitted THz radiation is very sensitive to the machine tuning, its power could vary by many orders of magnitude. We report on coherent THz signal intensities as a function of different machine parameters, such as beam energy, beam current, rf voltage and alpha tuning.

* R. Klein et al., Phys. Rev. ST. Accel. Beams vol. 11, 110701 (2008). ** J. Feikes et al., The Metrology Light Source: The First Electron Storage Ring Optimized for Generating Coherent THz Radiation, submitted to Phys. Rev. ST. Accel. Beams (2009).

• V. Judin, S. Hillenbrand, N. Hiller, A. Hofmann, E. Huttel, M. Klein, S. Marsching, A.-S. Müller, N.J. Smale, K.G. Sonnad, P.F. Tavares
  KIT, Karlsruhe
• H.W. Huebers
  Technische Universität Berlin, Berlin
• A. Semenov
  DLR, Berlin

Since a few years CSR-Radiation created in low alpha mode is provided by the ANKA light source of the KIT*. Depending on the bunch current, the radiation is emitted in bursts of high intensity. These bursts display a time evolution which can be observed only on long time scales with respect to the revolution period. The intensity of the emitted radiation during a burst is significantly increased w.r.t. steady state emission. Some users of the THz radiation don't require particularly constant emission characteristics and could profit from the higher intensity. A better understanding of the long term behaviour of those bursts could help to improve the conditions for those users. We have investigated THz radiation in multiturn mode with a hot electron bolometer. Its time response of 165ps allowed us to resolve the signals of individual bunches. Using a 6GHz LeCroy oscilloscope for data acquisition, we were able to save up to 1.6ms long signal sequences at a sampling rate of 20GS/s. This amount of data corresponds to over 4000 bunch revolutions and allows turn-by-turn signal tracking of desired bunches. In single bunch mode we are able to take segmented data to avoid a huge overhead.

* KIT - Karlsruhe Institute for Technology

• R. Takai, T. Honda, Y. Kobayashi, T.M. Mitsuhashi, T. Obina, M. Shimada, Y. Tanimoto
  KEK, Ibaraki

A hybrid fill mode has been tested at the Photon Factory storage ring (PF-ring). The hybrid fill mode consists of a train of low-current bunches and a high-current single bunch. Since a bunch-by-bunch feedback system was not available because of the high contrast of currents between the bunch train and the single bunch, we suppressed multibunch instabilities in the transverse and longitudinal planes by using the octupole magnets and RF phase modulation, respectively. We also suppressed single-bunch instabilities by controlling ring chromaticity. As a result, we successfully stored a 450 mA current with the hybrid fill mode: 1/2 filling (2.56 mA/bunch × 156) + 1 single bunch opposite to the bunch train (50 mA/bunch). The distribution of vacuum pressures along the ring was similar for the hybrid fill and the typical single-bunch mode. In this conference, we will present the results of this test experiment as well as some future subjects to be solved for the user operation.

• H. Zen, K. Hayashi, J. Yamazaki
  UVSOR, Okazaki
• M. Adachi, M. Katoh, T. Tanikawa, H. Zen
  Sokendai - Okazaki, Okazaki, Aichi
• M. Hosaka, Y. Taira, N. Yamamoto
  Nagoya University, Nagoya

UVSOR-II is a low emittance, 750 MeV synchrotron light source. Low emittance and low energy synchrotron light sources naturally suffered from short electron lifetime due to Touschek effect. Top-up operation is a solution for overcoming the effect. In the UVSOR-II, trials of multi-bunch top-up operation at the full energy were started from 2008. In the trials, we have succeeded in keeping the stored beam current around 300 mA for 12 hours. From this fiscal year, single bunch injection was started for single bunch user operations and for experiments on advanced light source development such as Free Electron Laser (FEL), Coherent Synchrotron Radiation (CSR), Coherent Harmonic Generation (CHG), which require single bunch or 2-bunch filling operation. We have already performed single bunch top-up operation in user time with the stored beam current of 50 mA. And FEL lasing with top-up operation was also achieved at the laser wavelength of 215 nm with the stored beam current of 130 mA / 2-bunch. In the FEL lasing experiment, we succeeded in keeping the average power of FEL around 130 mW for three hours.

• 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. 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.

• J.G. Power, M.E. Conde, W. Gai
  ANL, Argonne
• Z. Li
  SLAC, Menlo Park, California
• D. Mihalcea
  Northern Illinois University, DeKalb, Illinois

We report on the design of a 7 cell, standing wave, 1.3 GHz LINAC cavity and the associated beam dynamics studies for the upgrade of the drive beamline for the Argonne Wakefield Accelerator (AWA) facility. The LINAC design is a compromise between single bunch operation (100 nC @ 75 MeV) and minimizing the energy droop due to beam loadning along the bunch train during bunch train operation. The 1.3 GHz drive bunch train target parameters are: 75 MeV, 10-20 ns macropulse duration, 16x60nC microbunches; this is equivalent to a macropulse current and beam power of 80 Amps and 6 GW, respectively. Each LINAC structure accelerates approximately 1000 nC in 10 ns by a voltage of 11 MV at an RF power of 10 MW. Due to the short bunch train duration desired (~10 ns) and the existing frequency (1.3 GHz), compensation of the energy droop along the bunch train is difficult to accomplish with the two standard techniques: time-domain or frequency-domain beam loading compensation. Therefore, to minimize the energy droop, our design is based on a large stored energy LINACs. In this paper, we present our LINAC optimization method, detailed LINAC design, and beam dynamics studies of the drive beamline.

• D. Alesini, C. Biscari, A. Ghigo
  INFN/LNF, Frascati (Roma)

After a short description of the Frequency Multiplication Scheme of the CLIC drive beam we present the impact of beam loading in the RF deflectors. First order scaling laws for the beam loading have been obtained to compare the effects in CLIC with those in the Test Facility CTF3. A dedicated tracking code has been written to study the multi-bunch multi-turn beam dynamics and the results are presented. Possible solutions to mitigate the beam loading effects such as the use of multiple RF deflectors are shown.