Keyword: laser
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MOAL4 First Results from the Bunch Arrival-Time Monitor at the SwissFEL Test Injector pick-up, gun, feedback, electron 8
 
  • V.R. Arsov, M.M. Dehler, S. Hunziker, M.G. Kaiser, V. Schlott
    PSI, Villigen PSI, Switzerland
  
  Non-destructive electron bunch arrival-time monitors (BAMs) with resolution <10 fs, sensitivity down to 10 pC and high intrinsic bandwidth for double bunch detection are required for reliable operation of SwissFEL. To achieve this ultimate goal, such a monitor based on a Mach-Zehnder electro-optical intensity modulator has been under development at the SwissFEL Test Injector. The high timing precision is derived by a stable pulsed optical reference system. The first BAM is located before the bunch compressor where the bunch energy is 230 MeV and the pulse length is approximately 3 ps. At this position, the bunch arrival time is sensitive to the laser- and gun timing. In this paper, we report on the commissioning of the RF- and optical front ends, the first arrival-time jitter and drift measurements with the entire system, as well as correlation of the arrival-time with different machine and environmental parameters. We achieve a resolution of 20 fs down to 60 pC.  
slides icon Slides MOAL4 [1.228 MB]  
 
MOBL1 Instrumentation and Results from the SwissFEL Injector Test Facility radiation, diagnostics, transverse, electron 12
 
  • R. Ischebeck, V.R. Arsov, S. Bettoni, B. Beutner, M.M. Dehler, A. Falone, F. Frei, I. Gorgisyan, Ye. Ivanisenko, P.N. Juranic, B. Keil, F. Löhl, G.L. Orlandi, M. Pedrozzi, P. Pollet, E. Prat, T. Schietinger, V. Schlott, B. Smit
    PSI, Villigen PSI, Switzerland
  • P. Peier
    DESY, Hamburg, Germany
  
  The SwissFEL Injector Test Facility (SITF) has been equipped with numerous prototype diagnostics (BPMs, screen monitors, wire scanners, optical synchrotron radiation monitor, compression (THz) monitor, bunch arrival time monitor, EO spectral decoding monitor, charge and loss monitor) specifically designed for the low charge SwissFEL operation modes. The design of the diagnostics systems and recent measurement results will be presented.  
slides icon Slides MOBL1 [35.165 MB]  
 
MOBL3 Electron Bunch Diagnostic at the Upgraded ELBE Accelerator: Status and Challenges ELBE, electron, diagnostics, pick-up 23
 
  • M. Kuntzsch, S. Findeisen, M. Gensch, B.W. Green, J. Hauser, S. Kovalev, U. Lehnert, P. Michel, F. Röser, Ch. Schneider, R. Schurig
    HZDR, Dresden, Germany
  • A. Al-Shemmary, M. Bousonville, M.K. Czwalinna, T. Golz, H. Schlarb, B. Schmidt, S. Schulz, N. Stojanovic, S. Vilcins
    DESY, Hamburg, Germany
  • E. Hass
    Uni HH, Hamburg, Germany
  
  Within the ELBE upgrade towards a Center for High Power Radiation Sources (HSQ), a mono energetic positron, a liquid lead photo neutron source and two new THz sources have been installed at the superconducting electron linac at ELBE. A variety of established as well as newly developed electron beam diagnostics were installed and tested. In this paper we want to present first results achieved with the currently existing prototype beam arrival time and bunch compression monitors (BAM, BCM) as well as one versatile EOS set-up. Based on these future developements and upgrades are discussed.  
slides icon Slides MOBL3 [3.578 MB]  
 
MOCL1 Beam Instrumentation at the Accelerator Test Facility 2 electron, OTR, feedback, emittance 26
 
  • S.T. Boogert
    JAI, Egham, Surrey, United Kingdom
  • S.T. Boogert
    Royal Holloway, University of London, Surrey, United Kingdom
  
  The Accelerator Test Facility 2 (ATF2) is a scaled demonstrator system for final focus beam lines of linear high energy colliders. Four OTR (Optical Transition Radiation) monitors have been installed at the ATF2. Major characteristics is the fast measurement of projected (2D) and intrinsic (4D) emittances and the coupling corrections with skew quadrupole magnets at the upstream. The high resolution cavity beam position monitor (BPM) system is a part of the ATF2 diagnostics. Two types of cavity BPMs are used, C-band operating at 6.426 GHz, and S-band at 2.888 GHz with an increased beam aperture. The resolution of the C-band system with attenuators was determined to be approximately 250 nm and 1 μm for the S-band system. Without attenuation the best recorded C-band cavity resolution was 27 nm. A laser-wire transverse electron beam size measurement system has been constructed and operated at the ATF2 beam line at KEK. A special set of electron beam optics was developed to generate an approximately 1μm vertical focus at the laser-wire location. Systematic measurements of a micron beam size have been successfully executed.  
slides icon Slides MOCL1 [6.059 MB]  
 
MOPC32 Development Status of Optical Synchronization for the European XFEL XFEL, DESY, coupling, shielding 135
 
  • C. Sydlo, M.K. Czwalinna, M. Felber, C. Gerth, T. Lamb, H. Schlarb, S. Schulz, F. Zummack
    DESY, Hamburg, Germany
  • S. Jabłoński
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  
  Precise timing synchronization on the femtosecond timescale is crucial for time resolved experiments at modern free-electron lasers (FELs) like FLASH and the upcoming European XFEL. The required precision can only be achieved by a laser-based synchronization system. The pulsed laser-based scheme at FLASH, based on the distribution of femtosecond laser pulses over actively stabilized optical fibers, has evolved over the years from a prototype setup to a mature and reliable system. At the same time, the present implementation serves as prototype for the synchronization infrastructure at the European XFEL. Due to a factor of ten increase of the length of the accelerator and an increased number of timing-critical subsystems, new challenges arise. This paper reports on the current development progress of the XFEL optical synchronization, discusses major complications and their solutions.  
 
MOPC33 Status of the Fiber Link Stabilization Units at FLASH electron, free-electron-laser, FEL, polarization 139
 
  • F. Zummack, M.K. Czwalinna, M. Felber, T. Lamb, H. Schlarb, S. Schulz, C. Sydlo
    DESY, Hamburg, Germany
  • S. Jabłoński
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  
  State-of-the-art X-ray photon science with modern free-electron lasers (FEL) like FLASH and the upcoming European X-ray Free-Electron Laser Facility (XFEL) requires timing with femtosecond accuracy. For this purpose a sophisticated pulsed optical synchronization system distributes precise timing via length-stabilized fiber links throughout the entire FEL. Stations to be synchronized comprise bunch arrival time monitors, RF stations and optical cross-correlators for external lasers. The different requirements of all those stations have to be met by one optical link-stabilization-unit (LSU) design, compensating drifts and jitter in the distribution system down to a fs-level. Five years of LSU operation at FLASH have led to numerous enhancements resulting in an elaborate system. This paper presents these enhancements, their impact on synchronization performance and the latest state of the LSUs.  
 
MOPC37 Longitudinal Bunch Profile Reconstruction Using Broadband Coherent Radiation at FLASH radiation, longitudinal, electron, transverse 154
 
  • E. Hass
    Uni HH, Hamburg, Germany
  • C. Behrens, C. Gerth, B. Schmidt, M. Yan
    DESY, Hamburg, Germany
  • S. Wesch
    HZB, Berlin, Germany
  
  The required high peak current in free-electron lasers is realized by longitudinal compression of the electron bunches to sub-picosecond length. Measurement of the absolute spectral intensity of coherent radiation emitted by an electron bunch allows monitoring and reconstruction of the longitudinal bunch profile. To measure coherent radiation in the teraherz and infrared range a in-vacuum coherent radiation intensity spectrometer was developed for the free-electron laser in Hamburg(FLASH). The spectrometer is equipped with five consecutive dispersion gratings and 120 parallel readout channels: it can be operated either in short (5-44 um) or in long wavelength mode (45-430 um). Fast parallel readout permits the monitoring of coherent radiation from single electron bunches. Large wavelength coverage and superb absolute calibration of the device allows reconstruction of the longitudinal bunch profile using Kramers-Kronig based phase retrieval technique. The device is used as a bunch length monitor and tuning tool during routine operation at FLASH. Comparative measurements with radio-frequency transverse deflecting structure show excellent agreement of both methods.  
 
MOPC39 Commissioning of a New Streak Camera at TLS for TPS Project synchrotron, storage-ring, longitudinal, feedback 159
 
  • C.Y. Liao, M.C. Chou, K.T. Hsu, K.H. Hu, C.H. Kuo, C.-C. Kuo, W.K. Lau, C.Y. Wu
    NSRRC, Hsinchu, Taiwan
  
  Taiwan Photon Source (TPS) is a 3 GeV synchrotron light source which is being construction at campus of National Synchrotron Radiation Research Center (NSRRC) in Taiwan. A new streak camera equipped with a 125/250 MHz synchroscan unit, a fast/slow single sweep unit, and a dual-time sweep unit is prepared for beam diagnostics, especially for the TPS. An ultra short femtosecond Ti-Sapphire laser was used to evaluate the sub-picosecond temporal resolution of the streak camera and the first beam measurements of the streak camera using synchrotron light from the existing 1.5 GeV Taiwan Light Source (TLS) were performed. The commissioning results are summarized in this report.  
 
MOPC40 Measurement of Longitudinal Bunch Profile and Twiss Parameters in SNS LINAC longitudinal, linac, SCL, SNS 163
 
  • A.V. Aleksandrov, C. Huang, Y. Liu, A.P. Shishlo, A.P. Zhukov
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
We are reporting on the latest progress in the longitudinal beam profile and emittance diagnostics development at SNS. In order to characterize the longitudinal phase space of the beam in the SNS 1GeV proton LINAC the bunch profile needs to be measured with a few picosecond resolution. The original SNS set of diagnostics included only four interceptive Feschenko-style longitudinal profile monitors in the normal conducting part of the LINAC at 100MeV. Two recently added systems are: a non-interceptive laser scanner in the injector at 2.5MeV and a novel non-interceptive method for longitudinal Twiss parameters measurement using the beam position monitors in the Super Conducting LINAC (SCL) at 300MeV. This paper presents details of these two diagnostics and discusses their performance, resolution limitations and future development plans. 		 
poster icon Poster MOPC40 [8.865 MB]  
 
MOPC42 Novel Pickup for Bunch Arrival Time Monitor pick-up, LEFT, transverse, simulation 170
 
  • A. Kalinin
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  For an optical-modulator-based BAM, main parameter of the pickup output signal is slope steepness. We suggest a novel pickup with flat thin electrodes in a transverse gap. Increasing the electrode width makes the steepness greater in the same extent as the signal increases. For a given width, reducing the electrode thickness allows to reach ultimate steepness. Wave processes in the pickup were investigated on a large scale model, using the technique described in *. The DESY 40GHz button pickup was used as a reference. It is shown that steepness of the flat electrode pickup can be achieved two times greater. It is also shown that a BAM electrode pickup has a remarkable feature: the steepness does not depend on electrode sizes, if the ratio w/G (a flat electrode pickup, the width and gap length) or d/D (a button pickup, the diameters) is kept constant. This makes pickup bandwidth that is of the order of c over 2G or 2D, a free parameter. For flat electrode pickup, the steepness can be kept as high with transition to a more practical bandwidth 20GHz. The investigation results are the base for a final pickup optimisation using electrodynamic simulation.
* A. Kalinin, “Pickup Electrode Electrodynamics Investigation”, WEPC26, this conference 		 
poster icon Poster MOPC42 [0.549 MB]  
 
MOPF03 Laser Diode Velocimeter-Monitor Based on Self-Mixing Technique target, feedback, scattering, radiation 200
 
  • A.S. Alexandrova, C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • A.S. Alexandrova, C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  
  Funding: Work supported within LA3NET which is funded by the European Commission under contract PITN-GA-2011-289191 and STFC under the Cockcroft Institute Core Grant No.ST/G008248/1.
Gas targets are important for a number of accelerator-based applications, in particular as cold targets for collision experiments and beam diagnostics purposes where gas jets have been successfully used as least intrusive beam profile monitors, however, detailed information about the gas jet is important for its optimization and the quality of the beam profile that can be measured with it. A laser velocimeter shall be used for an in-detail characterization of atomic and molecular gas jets and allow investigations into the jet dynamics. Existing methods are currently not efficient enough, hard to build, and rather expensive. A laser velocimeter based on the self-mixing technique can provide unambiguous measurements from a single interferometric channel, realizable in a compact experimental setup that can be installed even in radiation-exposed environments. In this contribution, an introduction to the underlying theory of self-mixing is given, before the design and functioning principle of the velocimeter is described in detail. Finally, preliminary experimental results with different solid targets are presented and an outlook on measurements with fluid and gaseous targets is given. 		 
poster icon Poster MOPF03 [1.045 MB]  
 
MOPF05 Operating Semiconductor Timepix Detector with Optical Readout in an Extremely Hostile Environment of Laser Plasma Acceleration Experiment vacuum, target, shielding, optics 208
 
  • L. Pribyl
    Czech Republic Academy of Sciences, Institute of Physics, Prague, Czech Republic
  
  The laser plasma acceleration (LPA) experiments produce very intensive electromagnetic pulses (EMP) complicating operation of sensitive electronic detectors. We present our experience with new optical readout and EMP shielding for hybrid silicon pixel detector Timepix*, which enabled its operation in an extremely hostile electromagnetic LPA environment. The Timepix detector provides a matrix of 256x256 spectroscopic channels with 55 μm pitch. An optical readout, battery powering and shielding against electromagnetic pulses (EMP) have been developed as part of the ELI Beamlines/IEAP project for the detector Timepix and it significantly improved its resistance to EMP with respect to previous setup using metallic cables for both data acquisition and powering. The new optical setup was successfully tested under vacuum at Prague Asterix Laser System (PALS) during experiments with laser pulses of energies up to 700 J and duration of 350 ps bombarding thin foil solid target. Electromagnetic field was measured both outside the vacuum chamber and inside. The recorded spectrometric data were analyzed and interpreted in a context of an independent experimental campaign run in parallel.
* X. Llopart et al.: Timepix, a 65k Programmable Pixel Readout Chip for Arrival Time, Energy and/or Photon Counting Measurements, Nucl. Instr. and Meth. in Phys. Res. A. Vol. 581 (2007), p485 		 
 
MOPF16 Sub-Micrometre Resolution Laserwire Transverse Beam Size Measurement System electron, transverse, OTR, photon 243
 
  • L.J. Nevay
    JAI, Egham, Surrey, United Kingdom
  • A.S. Aryshev, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • S.T. Boogert, P. Karataev, K.O. Kruchinin
    Royal Holloway, University of London, Surrey, United Kingdom
  • L. Corner, R. Walczak
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
  
  The laserwire system at the Accelerator Test Facility 2 (ATF2) is a transverse beam profile measurement system capable of measuring a micrometre-size electron beam. We present recent results demonstrating a measured vertical size of 1.16 ± 0.06 μm and a horizontal size of 110.1 ± 3.8 μm. Due to the high aspect ratio of the electron beam, the natural divergence of the tightly focussed laser beam across the electron beam width requires the use of the full overlap integral to deconvolve the scans. For this to be done accurately, the propagation of the 150 mJ, 167 ps long laser pulses was precisely measured at a scaled virtual interaction point.  
 
TUPC03 Commissioning and Diagnostics Development for the New Short-Pulse Injector Laser at FLASH emittance, electron, gun, SASE 353
 
  • T. Plath, J. Rönsch-Schulenburg, J. Roßbach
    Uni HH, Hamburg, Germany
  • H. Schlarb, S. Schreiber, B. Steffen
    DESY, Hamburg, Germany
  
  In order to extend the parameter range of FLASH towards shorter electron pulses down to a few fs SASE pulses, shorter bunches with very small charges of a few tens of picocoulombs are necessary directly at the photo injector. Therefore a new injector laser delivering pulses of 1 to 5 ps has been installed and commissioned. The influence of the laser parameters on the electron beam was studied theoretically. In this paper we discuss the required laser beam diagnostics and present measurements of critical laser and electron beam parameters.  
poster icon Poster TUPC03 [1.076 MB]  
 
TUPC05 Laser and Photocathode Gun Instrumentation for the ASTA Accelerator Test Stand at SLAC cathode, gun, LCLS, SLAC 357
 
  • J. Sheppard, W.J. Corbett, S. Gilevich, E.N. Jongewaard, J.R. Lewandowski, P. Stefan, T. Vecchione, S.P. Weathersby, F. Zhou
    SLAC, Menlo Park, California, USA
  
  An accelerator test stand has been constructed at SLAC to characterize laser-assisted photocathode processing, electron beam emission physics and front-end rf gun performance. The objective of the research program is to identify definitive ‘recipes’ for high-reliability cathode preparation resulting in high quantum efficiency and low beam emittance. In this paper we report on timing, optics and instrumentation for the Ti:Sapphire drive laser, diagnostics for the 1.6 cell photocathode gun and instrumentation for the resulting electron beam. The latter include a Faraday cup charge monitor, scintillator screen beam imaging for direct emittance measurements, and high-resolution imaging of the photocathode surface to diagnose the impact of laser processing for enhanced quantum efficiency.  
 
TUPC33 Femtosecond Stable Laser-to-RF Phase Detection for Optical Synchronization Systems controls, XFEL, polarization, monitoring 447
 
  • T. Lamb, M.K. Czwalinna, M. Felber, C. Gerth, H. Schlarb, S. Schulz, C. Sydlo, M. Titberidze, F. Zummack
    DESY, Hamburg, Germany
  • E. Janas
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  • J. Szewiński
    NCBJ, Świerk/Otwock, Poland
  
  Optical reference distributions have become an indispensable asset for femtosecond precision synchronization of free-electron lasers. At FLASH and for the future European XFEL, laser pulses are distributed over large distances in round-trip time stabilized fibers to all critical facility sub-systems. Novel Laser-to-RF phase detectors will be used to provide ultra phase stable and long-term drift free microwave signals for the accelerator RF controls. In this paper, we present the recent progress on the design of a fully integrated and engineered version of the L2RF phase detector, together with first experimental results demonstrating so-far unrivaled performance.  
poster icon Poster TUPC33 [18.910 MB]  
 
TUPC34 Precision Synchronization of Optical Lasers Based on MTCA.4 Electronics feedback, DESY, monitoring, XFEL 451
 
  • U. Mavrič, L. Butkowski, H.T. Duhme, M. Felber, M. Fenner, C. Gerth, P. Peier, H. Schlarb, B. Steffen
    DESY, Hamburg, Germany
  • T. Kozak, P. Predki
    TUL-DMCS, Łódź, Poland
  
  Optical laser have become an integral part of free-electron laser facilities for the purposes of electron bunch generation, external seeding, diagnostics and pump-probe experiments. The ultra-short electron bunches demand a high timing stability and precision synchronization of the optical lasers. In this paper, we present the proof-of-principle for a laser locking application implemented on a MTCA.4 platform. The system design relies on existing MTCA.4 compliant off-the-shelf modules that are available on the market or have been developed for other applications within the particle accelerator community. Besides performance and cost, we also tried to minimize the number of out-of-crate components. Preliminary measurements of laser locking at the FLASH and REGAE particle accelerators are presented, and an outlook for further system development in the area of laser-to-RF synchronization is given.  
 
TUPC39 Dispersive Fourier-Transform Electrooptical Sampling for Single-Shot Modulation Measurement in a Proton-Driven Plasma Wakefield Accelerator proton, plasma, radiation, transverse 467
 
  • O. Reimann
    MPI-P, München, Germany
  • R. Tarkeshian
    MPI, Muenchen, Germany
  
  The concept of proton-driven plasma wakefield acceleration has recently been proposed as a means of accelerating a bunch of electrons to high energies with very high gradients, and a demonstration experiment (AWAKE) at CERN is now under development. For this a clear understanding of the temporal and spatial modulation of the proton driver bunches after propagating the plasma channel is essential. A single-shot electrooptical sampling system using dispersive Fourier-transform exploiting transverse coherent transition radiation* is proposed here to determine the bunch modulation and field properties in the frequency domain. Frequencies up to the terahertz region with a resolution of less than 10 GHz are measurable. The system with a closed optical fiber path is based on a semiconductor laser source to achieve easy handling and robustness. The principle idea, estimations of the required sensitivity, and first experimental results are presented.
* Pukhov, A. et al. Phys. Rev.ST Accel. Beams 15 (2012) 		 
 
TUPC40 Bunch Length Measurements Using Correlation Theory in Incoherent Optical Transition Radiation OTR, electron, radiation, longitudinal 471
 
  • B. Smit, F. Frei, R. Ischebeck, G.L. Orlandi, V. Schlott
    PSI, Villigen PSI, Switzerland
  
  Funding: Paul Scherrer Institut (PSI)
As Free Electron Lasers create ultra-short bunch lengths, the longitudinal diagnostic for such femto-second bunches becomes more difficult. We suggest a bunch length method using the spectral analysis of incoherent Optical Transition Radiation (OTR) in the visible frequency domain. The frequency response of OTR is taken by inserting an aluminium coated silicon wafer into the electron beam. The OTR light is collected with mirror optics into an optical fibre, which is coupled to a spectrometer (334 THz to 1500 THz). The resolution of the spectrometer allows us to measure bunch length lower than 100 fs rms. Bunch length was varied from 100 femto-seconds down to a few femto-seconds. The spectral response of Optical Transition Radiation (OTR) showed an increase of the correlation between neighbouring frequencies as bunch length was reduced. 		 
 
TUPC41 A Femtosecond Resolution Electro-Optic Diagnostic Using a Nanosecond-Pulse Laser diagnostics, CLIC, alignment, longitudinal 474
 
  • S.P. Jamison
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • W.A. Gillespie, D.A. Walsh
    University of Dundee, Nethergate, Dundee, Scotland, United Kingdom
  
  Funding: We gratefully acknowledge support under CERN collaboration agreement KE1865/TE
Electro-optic longitudinal profile diagnostic systems with intrinsically improved reliability and a time resolution of 20 fs rms are being developed for CLIC. Exploiting the electro-optic effect, the bunch electric field 'pulse carves' an optical replica from a narrow bandwidth nanosecond duration laser probe. All-optical characterisation of the optical replica is via spectrally resolved auto-correlation, providing a sub-20fs resolution capability. An optical parametric amplification stage following the pulse carving, and driven by same nanosecond laser that provides the probe, enables sufficient intensity for single-shot measurement. In basing the optical system on nanosecond Q-switched lasers, bypassing complex femtosecond laser systems, the potential for robust instrumentation development is enhanced. The bandwidth limitations of the electro-optic materials are being addressed through investigations into multiple crystal detectors, and THz induced second harmonic generation on metal surfaces. Experimental results on the optical subsystems, using laser-produced THz as an electron bunch mimic, are presented together with performance projections for the integrated system. 		 
 
TUPF03 Performance Assessment of Wire-Scanners at CERN LHC, SPS, CERN, synchrotron 499
 
  • G. Baud, B. Dehning, J. Emery, J-J. Gras, A. Guerrero, E.P. Piselli
    CERN, Geneva, Switzerland
  
  This article describes the current fast wire-scanner devices installed in circular accelerators at CERN with an emphasis of the error studies carried out during the last two runs. At present the wire-scanners have similar acquisition systems but are varied in terms of mechanics. Several measurement campaigns were performed aimed at establishing optimal operational settings and to identify and assess systematic errors. In several cases the results led to direct performance improvements while in others this helped in defining the requirements for new detectors.  
poster icon Poster TUPF03 [1.040 MB]  
 
TUPF05 Particle Tracking for the FETS Laser Wire Emittance Scanner dipole, simulation, diagnostics, emittance 503
 
  • J.K. Pozimski
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
  • S.M. Gibson
    Royal Holloway, University of London, Surrey, United Kingdom
  
  The Front End Test Stand (FETS) is an R&D project at Rutherford Appleton Laboratory (RAL) with the aim to demonstrate a high power (60 mA, 3 MeV with 50 pps and 10 % duty cycle), fast chopped H− ion beam. The diagnostics of high power particle beams is difficult due to the power deposition on diagnostics elements introduced in the beam so non-invasive instrumentation is highly desirable. The laser wire emittance scanner under construction is based on a photo-detachment process utilizing the neutralized particles produced in the interaction between Laser and H− beam for beam diagnostics purposes. The principle is appropriate to determine the transversal beam density distribution as well as the transversal and longitudinal beam emittance behind the RFQ. The instrument will be located at the end of the MEBT with the detachment taking place inside a dipole field. Extensive particle tracking simulations have been performed for various settings of the MEBT quadrupoles to investigate the best placement and size of the 2D scintillating detector and to determine the range and resolution of the instrument. Additionally the power distribution in the following beam dumps has been determined.  
 
TUPF14 Description of Laser Transport and Delivery System for the FETS Laserwire Emittance Scanner coupling, diagnostics, emittance, focusing 527
 
  • A. Bosco, G.E. Boorman, S. Emery, S.M. Gibson
    Royal Holloway, University of London, Surrey, United Kingdom
  • C. Gabor
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  • T. Hofmann
    CERN, Geneva, Switzerland
  • A.P. Letchford
    STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
  • J.K. Pozimski, P. Savage
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
  
  A beam emittance monitor for H− beams based on laser-induced ions neutralization is being developed at the Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL). The laser system that will be used for the photo-neutralization of the H− beam is a fiber laser emitting 110 ns pulses at λ=1064nm, with a repetition rate of 30 kHz and peak power of 8 kW. The laser will be conveyed to the interaction area over a distance of 70 m via an optical fiber. An assembly of two remotely controlled motorized translation stages will enable the system to scan across the H− beam along its vertical profile. A motorized beam expander will control the output size of the collimated laser beam in order to enable the system to operate with different spatial characteristics of the ions beam. In this paper we present a full account of the laser characteristics, the optical transport system and the final delivery assembly. All the relevant measurements such as power, spatial and temporal characteristics of the laser, fiber transport efficiency and final delivery laser beam parameters will be reported.  
poster icon Poster TUPF14 [4.081 MB]  
 
TUPF15 Overview of Laserwire Beam Profile and Emittance Measurements for High Power Proton Accelerators linac, emittance, ion, CERN 531
 
  • S.M. Gibson, G.E. Boorman, A. Bosco
    Royal Holloway, University of London, Surrey, United Kingdom
  • G.E. Boorman, A. Bosco, S.M. Gibson
    JAI, Egham, Surrey, United Kingdom
  • C. Gabor
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
  • T. Hofmann
    CERN, Geneva, Switzerland
  • A.P. Letchford
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • J.K. Pozimski
    STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
  • J.K. Pozimski, P. Savage
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
  
  Laserwires were originally developed to measure micron-sized electron beams via Compton scattering, where traditional wire scanners are at the limit of their resolution. Laserwires have since been applied to larger beam-size, high power H− ion beams, where the non-invasive method can probe beam densities that would damage traditional diagnostics. While photo-detachment of H− ions is now routine to measure beam profiles, extending the technique to transverse and longitudinal emittance measurements is a key aim of the laserwire emittance scanner under construction at the Front End Test Stand (FETS) at the RAL. A pulsed, 30kHz, 8kW peak power laser is fibre-coupled to motorized collimating optics, which controls the position and thickness of the laserwire delivered to the H− interaction chamber. The laserwire slices out a beamlet of neutralized particles, which propagate to a downstream scintillator and camera. The emittance is reconstructed from 2D images as the laserwire position is scanned. Results from the delivery optics, scintillator tests and particle tracking simulations of the full system are reviewed. Plans to deploy the FETS laser system at the Linac4 at CERN are outlined.  
poster icon Poster TUPF15 [9.196 MB]  
 
TUPF22 Beam Halo Monitor Based on an HD Digital Micro Mirror Array controls, monitoring, transverse, radiation 557
 
  • B.B.D. Lomberg, C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • B.B.D. Lomberg, C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  Funding: This work is supported by the European Union under contract PITN-GA-2011-289485 and by STFC under the Cockcroft Institute Core Grant No. ST/G008248/1.
A beam halo monitor is an essential device to pursue studies of halo particles produced in any particle accelerator as to investigate the effects of disturbances, such as field kicks, gradient errors, etc. A fast, least intrusive, high dynamic range monitor will allow the detection and potentially control of particles at the tail of a transverse beam distribution. Light generated by a beam of charged particles is routinely used for beam diagnostic purposes. A halo monitor based on a digital micro-mirror device (DMD) used to generate an adaptive optical mask to block light in the core of the emitted light profile and hence limit observation to halo particles has been developed in close collaboration with CERN and University of Maryland. In this contribution an evolution of this monitor is presented. A high definition micro-mirror array with 1920x1080 pixels has been embedded into a MATLAB-based control system, giving access to even higher monitor resolution. A masking algorithm has also been developed that automates mask generation based on user-definable thresholds, converts between CCD and DMD geometries, processes and analyses the beam halo signal and is presented in detail. 		 
poster icon Poster TUPF22 [1.558 MB]  
 
TUPF26 Laser-Based Beam Instrumentation R&D within LA3NET electron, target, diagnostics, acceleration 567
 
  • C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  
  Funding: LA³NET is funded by the European Commission under Grant Agreement Number 289191.
Within LA3NET, Laser Applications for Accelerators are being developed by an international NETwork of more than 30 partner institutions from across the world. Laser-based beam instrumentation is at the core of this EU-funded project which will train 17 fellows during its four year project duration. In this contribution, we will present the consortium's recent research results in beam diagnostics, ranging from development of a laser velocimeter and laser emittance meter, over measurement of the bunch shape with electro-optical sampling in an electron accelerator and precision determination of electron beam energy with Compton backscattered laser photons to measurement of electron bunches with a time resolution of better than 20 femtoseconds. We will also provide a summary of past training events organized by the consortium and give an overview of future workshops, conferences and schools. 		 
 
WEAL2 Extremely Low Emittance Beam Size Diagnostics with Sub-Micrometer Resolution Using Optical Transition Radiation OTR, vacuum, electron, transverse 615
 
  • K.O. Kruchinin, S.T. Boogert, P. Karataev, L.J. Nevay
    Royal Holloway, University of London, Surrey, United Kingdom
  • A.S. Aryshev, M.V. Shevelev, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • B. Bolzon
    The University of Liverpool, Liverpool, United Kingdom
  • B. Bolzon, T. Lefèvre, S. Mazzoni
    CERN, Geneva, Switzerland
  
  Transverse electron beam diagnostics is crucial for stable and reliable operation of the future electron-positron linear colliders such as CLIC or Higgs Factory. The-state-of-the-art in transverse beam diagnostics is based on the laser-wire technology. However, it requires a high power laser significantly increases the cost of the laser-wire system. Therefore, a simpler and relatively inexpensive method is required. A beam profile monitor based on Optical Transition Radiation (OTR) is very promising. The resolution of conventional OTR monitor is defined by a root-mean-square of the so-called Point Spread Function (PSF). In optical wavelength range the resolution is diffraction limited down to a few micrometers. However, in * we demonstrated that the OTR PSF has a structure which visibility can be used to monitor vertical beam size with sub-micrometer resolution. In this report we shall represent the recent experimental results of a micron-scale beam size measurement. We shall describe the entire method including calibration procedure, new analysis, and calculation of uncertainties. We shall discuss the hardware status and future plans.
* P. Karataev et al., Physical Review Letters 107, 174801 (2011). 		 
slides icon Slides WEAL2 [5.120 MB]  
 
WEPC31 New Design of the 40 GHz Bunch Arrival Time Monitor Using MTCA.4 Electronics at FLASH and for the European XFEL XFEL, pick-up, DESY, diagnostics 749
 
  • M.K. Czwalinna, C. Gerth, H. Schlarb
    DESY, Hamburg, Germany
  • S. Bou Habib
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland
  • S. Korolczuk, J. Szewiński
    NCBJ, Świerk/Otwock, Poland
  • A. Kuhl
    Uni HH, Hamburg, Germany
  
  At free-electron lasers, today's pump-probe experiments and seeding schemes make high demands on the electron bunch timing stability with an arrival time jitter reduction down to the femtosecond level. At FLASH and the upcoming European XFEL, the bunch train structures with their high bunch repetition rates allow for an accurate intra-train stabilisation. To realise longitudinal beam-based feedbacks a reliable and precise arrival time detection over a broad range of bunch charges, which can even change from 1 nC down to 20 pC within a bunch train, is essential. Benefitting from the experience at FLASH, the current bunch arrival time monitors (BAMs), based on detection of RF signals from broad-band pick-ups by use of electro-optic modulators, are further developed to cope with the increased requirements. In this paper, we present the new BAM prototype, including an adapted electro-optical front-end and the latest development of the read-out electronics based on the MTCA.4 platform.  
 
WEPC32 Past, Present and Future Aspects of Laser-Based Synchronization at FLASH electron, controls, DESY, FEL 753
 
  • S. Schulz, M. Bousonville, M.K. Czwalinna, M. Felber, M. Heuer, T. Lamb, J.M. Müller, P. Peier, S. Ruzin, H. Schlarb, B. Steffen, C. Sydlo, F. Zummack
    DESY, Hamburg, Germany
  • T. Kozak, P. Predki
    TUL-DMCS, Łódź, Poland
  • A. Kuhl
    Uni HH, Hamburg, Germany
  
  Free-electron lasers, like FLASH and the upcoming European XFEL, are capable of producing XUV and X-ray pulses of a few femtoseconds duration. For time-resolved pump-probe experiments and the externally seeded operation mode it is crucial not only to stabilize the arrival time of the electron bunches, but also to achieve a synchronization accuracy of external lasers on the same timescale. This can only be realized with a laser-based synchronization infrastructure. At FLASH, a periodic femtosecond laser pulse train is transmitted over actively stabilized optical fibers to the critical subsystems. In this paper we report on the present status and performance of the system, as well as its imminent upgrades and new installations. These include the connection of FLASH2, electron bunch arrival time monitors for low charges, a new master laser pulse distribution scheme, all-optical synchronization of the pump-probe laser and arrival time measurements of the UV pulses on the e-gun photocathode. Along with the coming connection of the acceleration modules to the master laser and the switch of the low-level hardware to the uTCA platform, an outlook to improved feedback strategies is given.  
 
WEPC35 Progress Report of the Spectral Decoding Based EOS with Organic Pockels EO Crystals electron, radiation, background, LEFT 765
 
  • Y. Okayasu, S. Matsubara, H. Tomizawa
    JASRI/SPring-8, Hyogo-ken, Japan
  • T. Matsukawa, H. Minamide
    RIKEN ASI, Sendai, Miyagi, Japan
  • K. Ogawa
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  
  Funding: Grant-in-Aid for Scientific Research (Japan Society for the Promotion of Science, Grants No. 20612024 and No. 23360045)
So far, the temporal structure of ultrashort electron bunches has been extensively investigated by various kinds of electro-optic sampling (EOS) techniques, such as temporal, spectral and spatial decoding method, at several FEL accelerator facilities since early 2000’s. Inorganic Pockels EO crystals, i.e., GaP and ZnTe, have been generally utilized for the EOS. On the other hand, since mid-1980’s, organic nonlinear optical materials have been extensively investigated and DAST*, which has fast temporal response in the EO effect, was developed in 1986**. DAST is transparent in visible near to IR wavelength range and absorbent in 0.8-1.3 THz. We introduced the DAST crystal into the EOS and successfully demonstrated the first observation of the bunch charge distribution at the EUV-FEL accelerator, SPring-8 on February 2012***. Through the previous experiment, it is found that the EO signal intensity was gradually decreased. On March and April 2013, we prepared DAST crystals with variety of thickness and succeeded to compare EO signal intensities with different bunch charges. Recent results of both optical and structural analysis will be reported in addition to experimental results.
*4-N, N-dimethylamino-4’-N’-methyl stilbazolium tosylate
**S. Okada et al., Japan Patent Application 61-192404 (1986)
***Y. Okayasu et al., Phys. Rev. ST Accel. Beams 16, 052801 (2013)
 		 
 
WEPC38 Current Status of Development of Optical Synchronization System for PAL XFEL XFEL, FEL, feedback, LCLS 772
 
  • C.-K. Min, I. Eom, H.-S. Kang, B.R. Park, S.J. Park
    PAL, Pohang, Kyungbuk, Republic of Korea
  • K. Jung, J. Kim, J. Lim
    KAIST, Daejeon, Republic of Korea
  
  Optical synchronization system has been developed for higher quality PAL XFEL with low timing jitter since 2011. In last two years, laboratory test was successfully performed, and test in our accelerator environment is ongoing. In laboratory, we tested the synchronization of RF master oscillator and optical master oscillator, the stabilization of 610 m optical fiber link, and the remote optical-to-RF conversion. We report recent our development results and summarize on-going optical timing project.  
poster icon Poster WEPC38 [3.366 MB]  
 
WEPC40 Pickup Signal Improvement for High Bandwidth BAMs for FLASH and European - XFEL pick-up, simulation, DESY, resonance 778
 
  • A. Angelovski, R. Jakoby, A. Penirschke
    TU Darmstadt, Darmstadt, Germany
  • M.K. Czwalinna, H. Schlarb, C. Sydlo
    DESY, Hamburg, Germany
  • T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  
  In order to measure the arrival time of the electron bunches in low (20 pC) and high (1 nC) charge operation mode, new high bandwidth pickups were developed as a part of the Bunch Arrival-time Monitors (BAMs) for FLASH at DESY *. The pickup signal is transported via radiation resistant coaxial cables to the electro-optic modulator (EOM) **. Due to the high losses of the 40 GHz RF front-end the signal in the RF path is attenuated well below the optimal operation voltage of the EOM. To improve the overall performance, the signal strength of the induced pickup signal needs to be increased and at the same time the losses in the RF front-end significantly reduced. In this paper, the analysis towards improving the induced pickup signal strength is presented. Simulations are performed with the CST STUDIO SUITE package and the results are compared with the state of the art high bandwidth pickups.
* A. Angelovski et al., Phys. Rev. ST Accel. Beams 15, 112803 (2012)
** A. Penirschke et al., Proc. of IBIC2012, Tsukuba, Japan (2012) 		 
 
WEPC41 Comparative Analysis of Different Electro-Optical Intensity Modulator Candidates for the New 40 GHz Bunch Arrival Time Monitor System for FLASH and European XFEL pick-up, electron, insertion, free-electron-laser 782
 
  • A. Kuhl, J. Rönsch-Schulenburg, J. Roßbach
    Uni HH, Hamburg, Germany
  • M.K. Czwalinna, C. Gerth, H. Schlarb, C. Sydlo
    DESY, Hamburg, Germany
  • S. Schnepp
    ETH Zurich, Institute of Electromagnetic Fields (IFH), Zurich, Switzerland
  • T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  
  Funding: The work is supported by Federal Ministry of Education and Research of Germany (BMBF) within FSP 301 under the contract numbers 05K10GU2 and 05K10RDA.
The currently installed Bunch Arrival time Monitors (BAMs) at the Free electron LASer in Hamburg (FLASH) achieved a time resolution of less than 10 fs for bunch charges higher than 500 pC. In order to achieve single spike FEL pulses at FLASH, electron bunch charges down to 20 pC are of interest. With these BAMs the required time resolution is not reachable for bunch charges below 500 pC. Therefore new pickups with a bandwidth of up to 40 GHz are designed and manufactured*. The signal evaluation takes place with a time-stabilized reference laser pulse train which is modulated with an Electro-Optical intensity Modulator (EOM). The new BAM system also requires new EOMs for the electro-optical frontend. The available selection of commercial EOM candidates for the new frontend is very limited. In this paper we present a comparison between different EOM candidates for the new electro optical frontend.
* A. Angelovski et al. Proceedings Phys. Rev ST AB, DOI:10.1103/PhysRevSTAB.15.112803 		 
poster icon Poster WEPC41 [0.619 MB]  
 
WEPF01 Alignment of a Nozzle-Skimmer System for a Non Invasive Gas Jet Based Beam Profile Monitor alignment, vacuum, electron, ion 803
 
  • V. Tzoganis, C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • V. Tzoganis, C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  Funding: Work supported by EU under contract 215080, Helmholtz Association and GSI under contract VH-BG-328, STFC under the Cockcroft Institute Core Grant No.ST/G008248/1 and a Liverpool - Riken fellowship.
A non-invasive gas jet-based beam profile monitor has been developed in the QUASAR Group at the Cockcroft Institute, UK. This shall allow monitoring ultra-low energy, as well as high energy particle beams in a way that causes least disturbance to both, primary beam and accelerator vacuum. In this setup a nozzle-skimmer system is used to generate a thin supersonic curtain-shaped gas jet. However, very small diameters of both, the gas inlet nozzle and subsequent skimmers, required to shape the jet, have caused problems in monitor operation in the past. Here, an image processing based technique is presented which follows after careful manual initial alignment using a laser beam. An algorithm has been implemented in Labview and offers a semi-automated and straightforward solution for all previously encountered alignment issues. The procedure is presented in detail and experimental results are shown. 		 
poster icon Poster WEPF01 [0.863 MB]  
 
WEPF04 A New Compact Design of a Three-Dimensional Ionization Profile Monitor (IPM) IPM, DESY, simulation, beam-position 811
 
  • H.F. Breede, H.-J. Grabosch, M. Sachwitz, L.V. Vu
    DESY Zeuthen, Zeuthen, Germany
  
  FLASH at DESY in Hamburg is a linear accelerator, which uses superconducting technology to produce soft x-ray laser light ranging from 4.1 to 45 nm. To ensure the operation stability of FLASH, monitoring of the beam is mandatory. Two Ionization Profile Monitors (IPM) detect the lateral x and y position changes. The functional principle of the IPM is based on the detection of particles, generated by interaction of the beam with the residual gas in the beam line. The newly designed IPM enables the combined determination of the horizontal and vertical position as well as the profile. This is made possible by a compact monitor, consisting of a cage in a vacuum chamber, two micro-channel plates (MCP) and two repeller plates with toggled electric fields at the opposite sides of the MCPs. The particles created by the FEL beam, drift in a homogenous electrical field towards the respective MCP, which produces an image of the beam profile on an attached phosphor screen. A camera for each MCP is used for evaluation. This indirect detection scheme operates over a wide dynamic range and allows the detection of the center of gravity and the shape of the beam. The final design is presented.  
poster icon Poster WEPF04 [3.643 MB]  
 
WEPF05 An Electron Beam Detector for the FLASH II Beam Dump radiation, electron, vacuum, target 814
 
  • F. Perlick, J.D. Good, N. Leuschner, M. Sachwitz
    DESY Zeuthen, Zeuthen, Germany
  • G. Kube, M. Schmitz, K. Wittenburg, T. Wohlenberg
    DESY, Hamburg, Germany
  
  For the electron absorber at FLASH II a detector is developed to control the position, dimensions and profile of the electron beam. Scintillation light, emitted from a luminescent screen in front of the dump window, is reflected by a mirror, located in 2 m distance from the screen, and passes through a vacuum window. Two different optical systems will be installed redundantly for beam image transfer: a conventional lens-mirror-system and a system using a radiation-hard optical fibre bundle. A CCD camera, located in one and a half meter distance from the beam line, is used for the optical analysis. An experimental setup, where the terms of installation of the components correspond to the FLASH accelerator, has been built up in a lab to coordinate the interaction of the screen with the components of the optical system. It was shown that the resolution of the lens-mirror-system is about one line pair per millimeter. An experiment is set up to test the impact of radiation on the optical qualities of the fibre optic bundle by installing it onto a “radioactive hot spot” at the bunch compressor in the FLASH accelerator.  
poster icon Poster WEPF05 [1.926 MB]  
 
WEPF06 A Fast Switching Mirror Unit at FLASH vacuum, site, DESY, free-electron-laser 818
 
  • F. Perlick, J.D. Good, N. Leuschner, A.S. Ontoso, M. Sachwitz, L.V. Vu
    DESY Zeuthen, Zeuthen, Germany
  • H. Schulte-Schrepping
    DESY, Hamburg, Germany
  
  The Free Electron Laser (FLASH) at DESY Hamburg is a linac providing unique experimental opportunities to investigate the atomic structure and the properties of materials, nanoparticles, viruses and cells. At the experimental hall, the incoming FEL beam can be deflected towards five test sites by silicon mirrors mounted into vacuum vessels, of which one is operated in permanent switching mode, allowing the simultaneous use of the light at two different test sites. So far, the entire vacuum vessel with the mirror inside is moved into the beam by a linear motor. This results in high translatory inertia and, to compensate the vessel motion, requires vacuum bellows, which have a limited lifetime especially at higher switching frequencies. Therefore, in the recent design the mirror is shifted by piezo motors operated inside the vessel under ultra-high vacuum conditions. However, temperature measurements revealed that during continuous operation the motor reaches up to 90°C only when exposed to air, necessitating long breaks to allow it to cool. Therefore suitable cooling methods are being investigated to guarantee continuous operation of the motor under ultra-high vacuum conditions.  
poster icon Poster WEPF06 [2.431 MB]  
 
WEPF21 Scanning Wire Beam Position Monitor for Alignment of a High Brightness Inverse-Compton X-ray Source electron, scattering, free-electron-laser, alignment 856
 
  • M.R. Hadmack, E.B. Szarmes
    University of Hawaii, Honolulu, HI, USA
  
  Funding: US Department of Homeland Security DNDO ARI program GRANT NO. 2010-DN-077-ARI045-02
The Free-Electron Laser Laboratory at the University of Hawaii has constructed and tested a scanning wire beam position monitor to aid the alignment and optimization of a high spectral brightness inverse-Compton scattering X-ray source. X-rays are produced by colliding the 40 MeV electron beam from a pulsed S-band LINAC with infrared laser pulses from a mode-locked free-electron laser driven by the same electron beam. The electron and laser beams are focused to 60 micron diameters at the interaction point to achieve high scattering efficiency. This wire-scanner allows for high resolution measurements of the size and position of both the laser and electron beams at the interaction point to verify spatial coincidence. Time resolved measurements of secondary emission current allow us to monitor the transverse spatial evolution of the e-beam throughout the duration of a 4 microsecond macropulse while the laser is simultaneously profiled by pyrometer measurement of the occulted infrared beam. Using this apparatus we have demonstrated that the electron and laser beams can be co-aligned with a precision better than 10 microns as required to maximize X-ray yield. 		 
poster icon Poster WEPF21 [14.675 MB]  
 
WEPF24 Charge Monitors at the Relativistic Electron Gun for Atomic Exploration – REGAE electron, diagnostics, DESY, gun 868
 
  • H. Delsim-Hashemi, K. Flöttmann, M. Seebach
    DESY, Hamburg, Germany
  • S. Bayesteh
    Uni HH, Hamburg, Germany
  
  A new linac is commissioned at DESY mainly as the electron source for femtosecond electron diffraction facility REGAE (Relativistic Electron Gun for Atomic Exploration). REGAE comprises a photo-cathode gun followed by normal conducting 1.5 cell rf-cavity to provide sub pC charge electron-bunches of 2-5 MeV with a coherence length of 30nm. In order to produce and maintain such electron bunches, sophisticated single-shot diagnostics are desired e.g. emittance, energy, energy-spread and bunch-length measurement. There are three methods at REGAE for charge measurement. The most routine method is based on Faraday-cups that are distributed along machine and can provide charge reading down to ~50 fC. The second method, which is non-destructive, is a cavity based antenna that measures beam induced fields. A third method is based on beam-profile measurement diagnostics. By proper calibration of integral intensity that arrives at detector one can measure charges down to fC level. The last method has the potential to reach the limit of few electrons charge when state-of-the-art intensifiers are used in profile monitors.  
 
WEPF27 Coherent Ultraviolet Radiation Measurements of Laser Induced Bunching in a Seeded FEL radiation, bunching, FEL, electron 879
 
  • M. Veronese, A. Abrami, E. Allaria, M. Ferianis, E. Ferrari, M. Trovò
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • F. Cianciosi
    ESRF, Grenoble, France
  
  Optimization of the bunching process in a seeded FEL like FERMI@Elettra is an important aspect for machine operation. In this paper we discuss about the power detection of coherent radiation in the UV range as a valuable method for optimizing the bunching induced by the seeding process on the electron beam. Experimental results obtained at FERMI@Elettra are presented here. Measurements of UV coherent transition and diffraction radiation have been used to quantify the bunching produced by the seed laser at lower laser harmonics. The dependence of the laser induced CUVTR signal on various parameters is experimentally studied. Future upgrades and possibilities for bunching measurements at shortest wavelengths are also discussed.