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| MOO1A03 | Review of Synchrotron Radiation based Diagnostics for Transverse Profile Measurements | emittance, radiation, optics, synchrotron | 6 | ||
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The transverse particle beam emittance is a crucial accelerator parameter because it is directly related to the brilliance of a synchrotron light source or the luminosity of a particle beam collider. Therefore a precise online control of the beam profile is highly desirable from which the corresponding emittance can be calculated. In addition observation of the particle beam shape's time-like evolution allows to study effects as for example injection mismatch and dynamical beta beating which are important for smooth-running accelerator operation. Due to its non-destructive nature synchrotron radiation is a versatile tool for beam profile measurements and is used in nearly every accelerator. While in principle synchrotron radiation from insertion devices or bending magnets can be utilized, in reality most accelerators use bending magnet radiation based profile monitoring because of space limitations. There exist a number of different techniques in order to overcome limitations due to resolution broadening effects which can result in theoretical resolutions down to the sub-micron level. In this talk an overview over the methods presently applied in most accelerators will be given.
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| MOO2A02 | Electron Beam Diagnostics for the European X-Ray Free-Electron Laser | electron, emittance, laser, linac | 17 | ||
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At the European XFEL, dedicated diagnostic sections are located in the injector, downstream of the bunch compressors, in the beam distribution area and undulator systems. Very challenging is the measurement and control of the compression process based on magnetic chicanes in combination with off-crest acceleration in both fundamental and 3rd-harmonic structures. Non-linear effects, e.g. CSR or LSC, which also depend on the compression process may degrade the slice emittance or energy spread. Moreover, a beam energy jitter transforms into a time jitter in the magnetic chicanes, and the beam arrival time is of crucial importance for other synchronised laser systems, e.g. for diagnostics, seeding or pump-probe experiments. The overlap of the electron and photon beams in the up to 250m-long undulators is relevant for the lasing process. BPMs with high single-bunch resolution are being developed for orbit monitoring and beam based alignment procedures. The general layout of the electron beam diagnostics for the European XFEL is presented. The development status of various diagnostic components is discussed, and, where appropriate, experimental results obtained at FLASH* are presented.
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* Many special diagnostic tools and prototypes are being developed and tested at the Free-Electron LASer in Hamburg FLASH. |
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| MOO2A03 | FERMI@elettra Diagnostics | linac, undulator | 20 | ||
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FERMI@elettra is the fourth generation light source currently under construction at the Sincrotrone Trieste Laboratory. It is a seeded FEL based on the existing 1.0GeV Linac which will be fitted with FEL specific sub-systems like a new photoinjector and two bunch compressors to obtain in front of the undulator chain a stable and high quality beam. Due to the challeging beam parameters, the diagnostics play a key role for the successfull commissioning first, and then for a reliable operation of the new faciltiy. In this paper we give an overview on the FERMI diagnostics operating in the 6-D phase space along with some keynotes on the timing system which is an integral part of the longitudinal diagnostics.
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| MOD1A03 | Electron Beam Diagnostics for the ALBA Light Source | booster, linac, synchrotron, radiation | 27 | ||
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This paper presents the diagnostics systems that will be used to monitor the electron beam at ALBA, a 3 GeV 3rd generation synchrotron light source. The electron beam is characterized by measuring its transverse position in the beam pipe, beam current, transverse size and longitudinal structure. We provide a complete picture of all the systems to diagnose the electron beam along ALBA facility, not only in the Storage Ring but also in the injector system (Linac, Booster and transfer lines).
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| TUO1A03 | Beam Diagnostic Features of the ESRF Multibunch Feedback | feedback, kicker, pick-up, controls | 48 | ||
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The ESRF storage ring is now equiped with a set of multibunch feedback systems. The main goal of the implementation of these systems is to prevent longitudinal and transverse instabilities. However, beside this main function, these systems provide a powerful diagnostic to study the longitudinal and transverse beam dynamic and document operation problems. In this paper we give a short overview of these feedback systems and describe their diagnostics function in more detail.
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| TUPB02 | Stripline Transversal Filter Techniques For Sub-Picosecond Bunch Timing Measurements | feedback, synchrotron, controls, vacuum | 54 | ||
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Measurement of time of arrival of a particle bunch is a fundamental beam diagnostic. The PEP-II/ALS/BESSY/PLS longitudinal feedback systems use a planar stripline circuit structure to convert a 30 ps beam BPM impulse signal into a 4 cycle tone burst at the 6th harmonic of the accelerator RF frequency (roughly 3 GHz). A phase-detection technique is used to measure the arrival time of these BPM impulses with 180 fs rms single-shot resolution (out of a 330 ps dynamic range). Scaled in frequency, this approach is directly applicable to LCLS, FEL and other sub-fs regime pulse and timing measurements. The transversal circuit structure is applicable to measurement of microbunches or closely spaced bunches (the PEP-II examples make independent measurements at 2 nS bunch spacing) and opens up some new diagnostic and control possibilities. This paper reviews the principles of the technique, and uses data from PEP-II operations to predict the limits of performance of this measurement scheme for arrival phase measurement. These predictions are compared with results in the literature from electro-optic high-resolution sub-picosecond beam timing and phasing diagnostics.
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* Briggs, et al, "Prompt Bunch by Bunch Synchrotron Oscillation Detection by a Fast Phase Measurement", Proceedings of the IEEE Particle Accelerator Conference, 5/91, 1404-1406 |
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| TUPB04 | BPM detectors upgrade for the ELETTRA Fast Orbit Feedback | feedback, electron, controls, closed-orbit | 60 | ||
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The project of a fast feedback system to stabilize the closed orbit of the Elettra storage ring is in an advanced stage. All of the existing BPMs have been equipped with new digital detectors in order to provide precise and high-rate position measurements to the feedback system. A new beam position interlock system has also been installed to protect the vacuum chamber from synchrotron radiation produced by insertion devices. This paper presents features and performance of the new orbit measurement system and reports some preliminary results of the feedback commissioning.
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| TUPB07 | Electric -In-Air-X-Ray- Detectors for high Resolution Vertical Beam Position Measurement at the ESRF | feedback, dipole, vacuum, emittance | 69 | ||
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The tiny fraction of the very hard X-rays that fully penetrate the dipole absorber structure and enter the free air space behind it can be detected in different ways to yield precise information on the vertical characteristics of the electron beam. In addition to a system of imaging detectors to measure the emittance, a 2nd detector type was developed that yields a direct electric signal. It consists of a high-Z blade in conjuction with a small In-Air ionization slot that generates a direct strong electric signal allowing for nanometer resolution measurements of vertical beam motion in a spectrum upto 1KHz. The high resolution performance of this detector type is explained by the fact that it touches the heart and center of the beam whereas other devices (X-BPMs or e-BPMs) have to work on the edges or tails of the beam or feel the beam indirectly by wall-current pick-ups. The results obtained with prototypes will be presented together with the prospects of an installation of 8 units in 2007. The intrinsic advantages of this In-Air detector like costs and simplicity, thanks to a total absence of cooling and UHV requirements, will be emphasized.
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| TUPB11 | A laserwire beam profile measuring device for the RAL Front End Test Stand | ion, laser, electron, emittance | 81 | ||
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The Front End Test Stand at the Rutherford Appleton Laboratory (RAL) is being developed to demonstrate a chopped H- beam of 60 mA at 3 MeV with 50 pps and sufficiently high beam quality for future high-powered proton accelerators. As such, it requires a suite of diagnostic instruments to provide detailed measurements of the ion beam. Due to the high beam brightness and a desire to be able to have online instrumentation, a series of non-intrusive and non-destructive diagnostics based on laser-detachment are being developed. The progress that has been made towards construction of a laserwire instrument that can measure the beam profile at an arbitrary angle are described. In particular, the principle behind the instrument, the simulation and design of it and the vacuum vessel in which it will be mounted are given. In addition, the reconstruction software that will be used to reconstruct the 2D transverse beam density distribution from the profiles of the beam is described.
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| TUPB13 | Design Considerations of a Spectrometer Dipole Magnet for the Photo Injector Test facility at DESY in Zeuthen (PITZ) | dipole, emittance, booster, quadrupole | 87 | ||
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The goal of the Photoinjector Test Facility at DESY in Zeuthen (PITZ) is to test and optimise electron guns for FELs like FLASH and XFEL at DESY in Hamburg and study emittance conservation by using a matched booster cavity. The physical specifications of a second spectrometer for measurements after the booster cavity at the beam momentum range from 4 to 40 MeV/c will be described. It will be used for measurements of the momentum distribution and the longitudinal phase space using two methods. The first method combines the dipole magnet with a RF transverse deflecting cavity, the second combines it with a Cherenkov radiator whose light is measured by a streak camera. Especially the first method is aiming for a good resolution in order to determine slice momentum spread. The design has to meet the demands of all these techniques for a measurement with high resolution and a bunch train containing 7200 pulses of 1nC charge and a repetition rate of 10Hz. Since there is not enough space for a separate beam dump after the dispersive section the beam has to be transported to the dump of the main beamline.
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| TUPB17 | Diagnostics for the CTF3 Probe Beam Linac CALIFES | electron, emittance, linac, acceleration | 99 | ||
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CALIFES is the probe beam linac developed by the CEA/DAPNIA and LAL in the frame of the CFT3 collaboration at CERN. Its objective is to "mimic" the main beam of CLIC in order to measure the performances of the 30 GHz CLIC accelerating structures. The requirements on the bunched electron beam in terms of emittance, energy spread and bunch-length are quite stringent and lead to use the most advanced techniques: laser triggered photo-injector, velocity bunching, RF pulse compression… In order to tune the machine and assess its performances before delivering the beam to the test stand a complete suit of diagnostics is foreseen including charge monitor, beam position and video profile monitors, deflecting cavity, RF pick-up and analysis dipole. All these diagnostics will be interfaced to the CERN command/control network. A special effort has been done on the Video Profile Monitors that make use of both scintillation and OTR (Optical Transition Radiation) screens and are fitted with 2 optical magnifications to fulfill field of view and resolution performances (<20μm). Their performances can be checked via an integrated resolution pattern.
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| TUPB21 | Experience with Libera Beam Position Monitors at DELTA | beam-losses, kicker, storage-ring, pick-up | 111 | ||
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Libera beam posiotion monitor electronics have been installed at the electron storage ring Delta in order to extend the capabilities of the BPM system to turn-by-turn orbit measurements. This report covers the integration of Liberas into the beam diagnostics infrastructure at DELTA and its control system EPICS. Prior to their application in user runs the devices have undergone characterization measurements in a BPM teststand and during machine runs for accelerator physics. Results of these measurements are compared to measurements with DELTAs standard BPM electronics. The necessary clock and trigger signals are provided by a low-cost signal distribution device developed at DELTA.
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| TUPB23 | Design Considerations for Phase Space Tomography Diagnostics at the PITZ Facility | quadrupole, space-charge, emittance, electron | 117 | ||
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A major goal of the Photo Injector Test Facility at DESY in Zeuthen (PITZ) is to build and to optimise high brightness electron sources for SASE FELs where the detailed knowledge of the phase-space density distribution of the electron beam is very important. The current upgrade of the machine includes a diagnostic section suitable for transverse phase space tomography and multiscreen emittance measurement. The designed module should be capable of operation over a range of beam momenta between 15 and 40MeV/c. It mainly consists of four observation screens with three FODO cells in between them. An upstream section of a number quadrupoles is used to match the electron beam Twiss parameters to the tomography section. The design considerations of the tomography section and results from numerical simulations will be presented in this contribution.
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| TUPB30 | Applications of IEEE-1394 and GigE Vision Digital Camera in the TLS | controls, radiation, emittance, synchrotron | 138 | ||
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Digital cameras comply with IEEE-1394 and GigE Vision standard are applied for beam diagnostic applications at NSRRC. These cameras provide low distortion for image transmission over long distance and flexible camera parameters adjustment with remote interface. These digital interfaces include of FireWire and gigabit Ethernet. The wide bandwidth bus can reduce latency time and timing jitter effectively and provides high quality image transportation. It also provides lossless compressed image with high update rate. Experiences accompany with both kind of cameras will be summarized. System integration with control system, analysis and application will also include in the report.
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| TUPB32 | An RF Deflector for the Longitudinal and Transverse Beam Phase Space Analysis at PITZ | emittance, electron, single-bunch, electromagnetic-fields | 144 | ||
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A detailed characterization of the longitudinal and transverse phase space of the electron beam provided by the Photo Injector Test Facility at DESY in Zeuthen (PITZ) is required to optimize photo injectors for Free-Electron Laser (FEL) applications. By means of a RF deflector the transverse slice emittance and the longitudinal phase space can be analysed. In this paper we present the status of the RF deflector design. The analysis of the prospect diagnostics shows the possibility to achieve a time resolution of about 0.5 ps, and a longitudinal momentum resolution of 10-4. The influence of the deflector on the beam longitudinal and transverse phase space is analysed.
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| TUPC02 | Photo Injector Cathode Laser Beam Intensity and Pointing Position Diagnostics at PITZ | laser, cathode, monitoring, electron | 147 | ||
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A photo cathode laser with unique parameters is used at the Photo Injector Test facility at DESY in Zeuthen, PITZ. It is cabable of producing laser pulse trains consisting of up to 800 pulses with a repetition rate of 1 MHz where each laser pulse has a flat-top temporal profile. The knowledge of the laser stability is very important for the emittance measurements procedure. Therefore, a system for monitoring the laser beam intensity and pointing position stability was created at PITZ. It is capable of measuring the laser spot position and pulse intensity for each of the laser pulses in the train using a quadrant diode and a photomultiplier tube, respectively. Taking into account the laser beam spot transverse intensity distribution measured by a CCD camera allows to study the position of the laser spot on the photo cathode with a resolution of 8.3 um. Laser intensity measurements can be done for a wide dynamical range of intensities due to the tunable photo multiplier tube gain. The first experiments with the new system show very small laser spot position jitter on the cathode surface of about 20 um and laser intensity fluctuations of about 14 %.
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| TUPC05 | Screen studies at PITZ | emittance, electron, simulation, scattering | 153 | ||
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The Photo Injector Test facility at DESY in Zeuthen (PITZ) has been built to test and to optimize electron sources that fulfill the requirements of SASE FEL's such as FLASH and XFEL. Basic properties of the electron beam such as mean momentum, momentum spread, transverse emittance etc. are determined using measurement of the beam size on YAG or OTR screens. Detailed knowledge of the uncertainties and systematic errors associated with these measurements are important to understand the underlying beam physics. The screen stations consist of a screen set-up, an optical transmission line to a CCD camera, and the video data acquisition system. In this paper we make a detailed description of the screen based beam size measurement systems that we use at PITZ and discuss the systematic errors of uncertainties associated with each single element of a system.
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| TUPC06 | Coherent Radiation Studies For The FERMI@Elettra Relative Bunch Length Diagnostics | radiation, dipole, electron, synchrotron | 156 | ||
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Bunch compressors are key components of the seeded FEL FERMI@elettra. Assuring their stable operation requires multiple non-destructive diagnostics to provide error signals to the feedback systems. Both the energy and the peak current of the electron bunch have to be stabilized by the feedback systems. The peak current stabilization implies charge and bunch length stabilization. The latter will be achieved by a redundant diagnostics based on Coherent Synchrotron Radiation (CSR) and Coherent Diffraction Radiation (CDR). In this paper we describe a study of Coherent Radiation emission downstream bunch compressors as the source of a relative bunch length measurement diagnostics. The study evaluates the most critical parameters in the design of such a diagnostic using numerical integration to calculate the spectral angular properties of the radiation for both CSR and CDR.
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| TUPC07 | Design and Construction of the Multipurpose Dispersive Section at PITZ | dipole, quadrupole, emittance, electron | 159 | ||
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For the characterization of rf photo-electron guns a full set of beam parameters has to be measured. For this purpose a new high energy dispersive arm will be used at the Photo Injector Test Facility at DESY in Zeuthen (PITZ) in addition to the existing beam diagnostics. The multipurpose dispersive arm (HEDA1) is designed [1] for an electron energy range up to 40 MeV and will be put into operation in autumn 2007. It combines the functionality of (i) an electron spectrometer, (ii) a device for the characterization of the longitudinal phase space, and (iii) a transverse slice emittance measuring system. HEDA1 consists of a 180 degree dipole magnet followed by a slit, a quadrupole magnet, and two screen stations. One of the screen stations will be equipped with an optical read-out for a streak camera. We report about the detailed design of individual components and the construction progress.
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[1] S. Khodyachykh, et al., Proccedings of the 28th International FEL Conference, Berlin (2006). |
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| TUPC09 | Design of the cavity BPM system for FERMI@elettra | dipole, linac, coupling, simulation | 165 | ||
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The cavity Beam Position Monitor (BPM) is a fundamental instrument for a seeded FEL, as FERMI@elettra. It allows the measurement of the bunch trajectory non-destructively, on a shot-by shot basis and with sub-micron resolution. The high resolution the cavity BPM is providing relies on the excitation of the dipole mode, originated when the bunch passes off axis in the cavity. Here we present the electromagnetic (EM) design and the cold test of the prototype BPM developed for the FERMI@elettra. The design adopted a C-band cavity with its dipole mode at fDIP=6.5GHz. The prototype is actually fitted with two cavities: one for the position measurement and one for the generation of the reference signal for the demodulator. Furthermore, the design of the prototype electronics for the acquisition and processing of the BPM signals is presented. The adopted scheme consists of a down converter from C-band to the intermediate frequency, followed by an IQ demodulator to generate the base-band signal, proportional to the transverse beam position. The performed simulation session is presented as well which we run before building the hardware for bench tests.
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| TUPC10 | A transverse RF deflecting cavity for the FERMI@elettra project | emittance, electron, linac, optics | 168 | ||
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The layout of FERMI@elettra includes a high energy transfer line (TL) which brings the accelerated electron bunch to the FEL undulator chains. The TL optics has been designed according to several space constraints and with the purpose of including diagnostics for the complete characterization of the electron bunch just before the FEL process starts. Basing on such optics, this paper reports the study of the electron bunch deflection at nominal energy of 1.2 GeV for the measurement of the bunch length, of the transverse slice emittance and of the slice energy spread, coupled to a downstream dipole. The effect of the cavity on the electron beam was simulated by tracking code and the specification on the deflecting voltage was thus confirmed. Furthermore the RF design and electromagnetic simulations are also presented here.
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| TUPC11 | The Beam Diagnostics System for the FERMI@elettra Photoinjector | emittance, laser, linac, gun | 171 | ||
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The quality of the photoinjector high brightness electron beam plays a crucial role for the performance of the seeded FERMI@elettra FEL. Optimization of the gun is possible with an extensive characterization of the 5 MeV electron beam longitudinal and transverse phase space. The photoinjector diagnostics system includes interceptive instrumentation as YAG:Ce screens for transverse position and profile measurements and Faraday cups for the absolute beam charge measurements; a Cherenkov radiator coupled to a streak camera provides an accurate reconstruction of the longitudinal profile and a pepper pot is foreseen for the transverse emittance measurement. Information on beam transverse position and charge is obtained non-disruptively with respectively stripline BPMs and a current transformer. A dispersive beamline is also foreseen for the beam energy, energy spread and longitudinal phase space measurements. The diagnostics system performances and design principles are presented.
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| TUPC12 | FPGA based Frame Grabber for Video Beam Diagnostics | controls, radiation, injection, proton | 174 | ||
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TV-based accelerator diagnostics are widely used for machine operation and beam diagnostics. It is planned to renew the video memory modules of the TV monitor data acquisition systems for the injection and transfer lines at DESY. New FPGA based Frame Grabber (FG) modules were developed within this project. The modules are required to be able to work with different analog signal formats, to capture video frames on trigger and to provide live mode operation. The main feature of this FG is the possibility of reprogramming. This allows us to optimize its functionality, for example to operate with non-standard or corrupted video signals. This has proved especially useful for grabbing images from CCD-cameras suffering from radiation damage.
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| WEO1A01 | Sub-ps Timing and Synchronization Systems for Longitudinal Electron Bunch Profile Measurements | laser, electron, radiation, undulator | 204 | ||
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Precise timing and synchronization systems have become an increasingly important topic for next generation light sources. Particularly free electron lasers can emit X-ray pulses with pulse durations down to the few-tens of femtoseconds level. In order to utilize this potential temporal resolution for pump-probe experiments, a precise synchronization of the experimental laser to the X-ray pulse and stabilization of the electron beam arrival time at the undulators are mandatory. This requires a timing and synchronization system which can supply ultra-stable phase references over long distances, thus enabling the temporal stabilization of the electron beam to a sub-100 fs level. Furthermore, a precise timing and synchronization system renders possible extremely accurate measurements of the longitudinal electron bunch profile. This talk will give an overview of the status of existing sub-ps timing and synchronization systems and of systems currently under construction.
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| WEO1A03 | Instrumentation for Longitudinal Beam Gymnastics in FEL's and in the CLIC test facility 3 | electron, linac, radiation, pick-up | 215 | ||
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Built at CERN by an international collaboration, the CLIC Test Facility 3 (CTF3) aims at demonstrating the feasibility of a high luminosity 3TeV e+-e- collider by the year 2010. One of the main issues to be demonstrated is the generation of a high average current (30A) high frequency (12GHz) bunched beam by means of RF manipulation. At the same time, Free Electron Lasers (FEL) are developed in several places all over the world with the aim of providing high brilliance photon sources. These machines all rely on the production of high peak current electron bunches. The required performances put high demands on the diagnostic equipment and innovative longitudinal monitors have been developed during the past years. This paper gives an overview of the longitudinal instrumentation developed at ELETTRA and CTF3, where a special effort was made in order to implement at the same time non-intercepting devices for online monitoring, and destructive diagnostics which have the advantage of providing more detailed information.
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| WEO2A02 | Single Shot Longitudinal Bunch Profile Measurements by Temporally Resolved Electro-Optical Detection | electron, laser, resonance, linac | 221 | ||
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For the high-gain operation of a SASE FEL, extremly short electron bunches are essential to generate sufficiently high peak currents. At the superconducting linac of FLASH at DESY, we have installed an electro-optic experiment to probe the time structure of the electric field of single sub 200fs e-bunches. In this technique, the field-induced birefringence in an electro-optic crystal is encoded on a chirped ps laser pulse. The longitudinal electric field profile of the electron bunch is then obtained from the encoded optical pulse by a single-shot cross correlation with a 30 fs laser pulse using a second-harmonic crystal (temporal decoding). In the temporal decoding measurements an electro-optic signal of 180 fs FWHM was observed, and is close to the limit due to the material properties of the particular electro-optic crystal used. The measured electro-optical signals are compared to bunch shapes simultaneously measured with a transversly deflecting cavity.
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| WEPB03 | Femtosecond Yb-Doped Fiber Laser System at 1 um of Wavelength with 100-nm Bandwidth and Variable Pulse Structure for Accelerator Diagnostics | laser, electron, radiation, polarization | 235 | ||
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Laser-based diagnostic systems play an increasingly important role in accelerator diagnostics in, for instance, measurements of the electron bunch length. To date, the laser system of choice for electro-optic experiments has been the Ti:Sa laser. These offer nJ pulse energies at fixed repetition rate between 50-100 MHz, which is not well suited to the bunch structure of facilities such as FLASH (several hundred pulses with 1 MHz spacing at 1-5 Hz repetition rate).The limited robustness, stability and operability of Ti:Sa systems make them less than an ideal candidate for a continuously running measurement system requiring minimal maintenance. Fiber lasers represent a promising alternative, since gating and subsequent amplification is simple and of low cost, hence a pulse pattern corresponding exactly to the linac bunch pattern can be generated. Furthermore, these lasers offer superior robustness at a fraction of the cost of a Ti:Sa laser and have been shown to work without maintenance for several months and longer. Here, we present an ytterbium-doped fiber laser system with 80 nm bandwidth and multi-nJ pulse energy with adjustable bunch pattern for use in electro-optic experiments.
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| WEPB06 | Direct Comparison of the Methods of Beam Energy Spread Determination in the VEPP-4M Collider | collider, betatron, electron, photon | 244 | ||
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The VEPP-4M electron-positron collider is now operating with the KEDR detector for the experiment of precise measurement of tau-lepton mass. The nearest experimental program of the accelerator includes scan of the energy area below J/psi meson to search narrow resonances. The monitoring of beam energy spread is important to know the energy spread contribution into the total systematic error. In this report we discuss the application of several diagnostics for beam energy spread measurement. The data obtained with Compton BackScattering (CBS) technique* are compared with the value of the spread derived from the betatron motion of the beam**. The measurements by all the methods were done at the same accelerator run, i.e. the different diagnostics can be compared directly. The value of the energy spread was determined for a set of collider operating modes, covering the energy area from 1200 MeV up to 1843 MeV. Width of the J/psi and psi' resonance measured with the KEDR detector is used as a reference.
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References*N. Muchnoi et al. //Proceed. of EPAC 2006, Edinburg, Scotland, TUPCH074**T. Nakamura et al. // Proceed. of the 2001 Particle Accelerator Conference, Chicago, p. 1972-1974. |
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| WEPB13 | Focusing of Optical Transition and Diffraction Radiation by a Spherical Target | target, electron, radiation, focusing | 259 | ||
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During the last few years Transition Radiation (TR) and Diffraction Radiation (DR) have been intensively studied for different applications such as diagnostics of electron beam size, emittance, length, energy spread, etc. For extremely high-energy electrons the broadening of TR (DR) spatial distribution due to “pre-wave” zone effect [*] leads to distortion of the radiation characteristics and decreasing of photon concentration per unit square detector. In papers [**,***] it was shown that using a spherical target one can make TR (DR) distribution in the pre-wave zone identical to a far-field one. To verify our approach we carried out an experiment at KEK-ATF extraction line with electron beam energy of 1.28 GeV using a spherical target to focus optical TR (DR) at the distance of L=440 mm which corresponds to an extreme pre-wave zone. We also measured OTR (ODR) characteristics from a flat target in order to compare them with OTR (ODR) characteristics from the spherical one. We clearly observed that OTR (ODR) angular distribution from the spherical target is narrower than from a flat one and it’s very similar to a far-field zone distribution as it was predicted by the theory.
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* V. A.Verzilov, PLA 273(2000)135** P. V.Karataev, PLA 345(2005)428*** A. P. Potylitsyn and R. O. Rezaev, NIMB 252(2006)44 |
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| WEPB18 | Electron Beam Temperature Measurements at the Fermilab Medium Energy Electron Cooler | electron, radiation, antiproton, optics | 268 | ||
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The Fermilab Recycler ring employs an electron cooler to store and cool 8.9-GeV antiprotons. The cooler is based on an electrostatic accelerator (Pelletron) working in an energy-recovery regime. Several techniques for determining the characteristics of the beam dynamics have been investigated. Beam temperature measurements using OTR in conjunction with a Pepper-pot have been made at several settings of the upstream optics of the machine. Without temperature the pepper-pot hole images would have sharp boundaries. A finite temperature makes these boundaries broader. Thus, comparison of the ratios of the hole image boundaries and intensities is a measure of the beam temperature. In this paper we report the results so far obtained using this technique.
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| WEPB19 | Digital Analysis of Beam Diagnostic Noise | coupling, proton, instrumentation, pick-up | 271 | ||
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Results will be presented of recently developed, VME-based electronic modules, a digital beam position monitor (dBPM) and a logarithmic current measurement electronics (VME-LogIV). The dBPM is based on digital receiver technology and processes the signals from 4 pick-up coils. Features of the dBPM are the direct frequency down-converting of the RF 2nd harmonic 101.26MHz) signals (no analogue LO), the remote control of the front end amplifier and the online measurement of individual channel overall gain using 101.31 MHz pilot signals. Various data rates for position measurements at up to 10 kHz are possible. The VME-LogIV can simultaneously measure up to 32 channels at an effective sampling frequency of 5 kHz for the multiple wire profile monitors, also called harps. Fluctuations up to a few kHz of the beam intensity and beam position can thus be analyzed in detail with both of these new systems. Fluctuations from different dBPMs can be compared using coherence spectra measurement. The origin of the VME-LogIV noise can be analyzed using power and coherence spectra, and compared to the noise of the ion source. The results of this analysis will be discussed.
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| WEPB23 | Beam Diagnostics Development for the Cryogenic Storage Ring CSR | ion, electron, pick-up, cryogenics | 283 | ||
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A cryogenic storage ring is under construction at the MPI-K Heidelberg. It consists of electrostatic elements and has a circumference of ~35m. The CSR shall be used for storage of rotationally non-excited molecules and highly charged ions, therefore extremely low temperatures (<4K) and gas pressures (10-15 mbar) are required. The ring shall also be operational at room temperature and bakeable to at least 300°C. The maximum energy of singly charged ions is 300keV, intensities will be in the range 1nA – 1uA. For the mass range, A<100 is taken as reasonable design value, in later stages of CSR operation experiments with heavier ions are foreseen. Due to the exceptional boundary conditions we are working on new or further developments for most of the diagnostics devices. For example our RGMs have to produce their own local pressure bumps. The MCPs have to work at temperatures around 4K. The beam position pickups shall be operated in resonant mode for increased sensitivity. Our beam profiler will use secondary electrons from a stopper plate, which allows beam imaging in the intensity range 102 to 1012 pps. For intensity measurements a SQUID CCC system is under discussion.
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| WEPB24 | Machine Protection and Interlock Systems at Synchrotron SOLEIL | vacuum, storage-ring, booster, synchrotron | 286 | ||
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SOLEIL is a third generation Synchrotron radiation source located in France near Paris, having the classical accelerator structure consisting of a Linac pre-accelerator, a Booster accelerator and a Storage Ring, which are connected by two transfer lines[1]. Since January, the Storage Ring delivers photon beam to 9 beamlines. In order to protect the very sensitive and essential equipment during machine operation, (vacuum chambers, vacuum valves, mirrors, etc.) an interlock system has been implemented. This system is based on industrial and autonomous PLC (Programmable Logic Controller). This paper describes each level of the interlock chain from the diagnostics and vacuum sensors and processes, up to the backbone of the interlock system which stops the RF system.
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| WEPB25 | Time Domain Measurements at Diamond | electron, photon, single-bunch, synchrotron | 289 | ||
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We present a set of four complementary measurements of the synchrotron visible light to characterise the stored electron beam at Diamond in the time domain. The electron bunch profiles and its evolution is measured with picosecond accuracy using a dual sweep streak camera. The beam dynamics are also given by a fast photodiode connected to a fast oscilloscope. The fill pattern is measured using a time correlated single photon counting system which has a high dynamic range for bunch purity measurement, and a fast averaging card which gives the fill structure with high accuracy within a short integration time. We describe our set of instruments, discuss their performance and show first results from measurements of Diamond's properties.
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| WEPB29 | Bunch-by-Bunch Longitudinal Diagnostics at DAΦNE by IR Light | electron, positron, synchrotron, single-bunch | 298 | ||
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Compact uncooled HgCdTe semiconductor detectors optimized in the mid-IR range have been used to record time resolved single bunch synchrotron radiation (SR) emissions from the DAΦNE e- main ring. These devices allow a low cost bunch-by-bunch longitudinal diagnostics. Indeed, the detectors make possible to record a train of 2.7 ns long bunches per turn. A comparison with synchrotron light signals coming from the e+ ring is stimulating but at DAΦNE only two SR beamlines are operational and because of the lack of apertures in the main wall no easy alternatives exist for the e+ ring. To solve the problem, a compact SR port has been considered and is going to be implemented on the positron ring. A small dedicated vacuum chamber with a ZnSe infrared window and remote controlled mirrors will be installed to focus the light on the IR detectors. The source characteristics have been simulated and the optical system with the complete acquisition system will be described. When ready, the real time comparison between data collected on the two beams will be performed improving accelerator diagnostics and as a major tool to increase the stored currents in the e+ ring and the collider luminosity.
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| WEPB31 | Injector Diagnostics Overview of SPIRAL2 Accelerator | pick-up, ion, linac, rfq | 304 | ||
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The SPIRAL2 project is based on a multi-beam driver in order to allow both ISOL and low-energy in-flight techniques to produce Radioactive Ion beams (RIB). A superconducting light/heavy-ion linac capable of accelerating 5 mA deuterons up to 40 MeV and 1 mA ions up to 14.5 MeV/u is used to bombard both thick and thin targets. These beams could be used for the production of intense RIB by several reaction mechanisms (fusion, fission, transfer, etc.). The post acceleration of RIB in the SPIRAL2 project is assured by the existing CIME cyclotron. SPIRAL2 beams, both before and after acceleration, can be used in the present experimental area of GANIL. The construction phase of SPIRAL2 is being started since the 1st of July 2005. An injector design overview is presented with diagnostics used to tune and qualify beams.
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| WEPC07 | Injection Diagnostics Using Triggered Bunch-by-Bunch Data Acquisition | injection, kicker, collider, storage-ring | 322 | ||
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Quality of injection is very important for reliable and successful operation of colliders and light sources. In this paper we present a technique for real-time monitoring of injection transients in storage rings. We also demonstrate how the data can be used for tuning the injection system. A novel data processing method, coupled with triggered bunch-by-bunch data acquisition system enables one to monitor the effects of the adjustments nearly in real time. The acquisition and postprocessing technique will be illustrated with the data from PEP-II and DAΦNE.
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| WEPC08 | Fiberoptics-Based Instrumentation for Storage Ring Beam Diagnostics | coupling, synchrotron, photon, synchrotron-radiation | 325 | ||
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We present the results of our experiments at the Advanced Light Source concerning the coupling of synchrotron radiation into optical fibers. Many beam diagnostic devices in today's synchrotron rings make use of the radiation emitted by the circulating particles. Such instruments are placed in close proximity of the accelerator, where in many instances they cannot be easily accessed for safety consideration, or at the end of a beamline, which, because of its cost, can only move the light port a few meters away from the ring. Our method, suitable for all those applications where the longitudinal properties of the beam are measured (i.e. bunch length, phase, etc.), allows placing the diagnostic instruments wherever is more convenient, up to several hundreds of meters away from the tunnel. This would make maintaining and replacing instruments, or switching between them, possible without any access to restricted areas. Additionally, one can use the vast array of optoelectronic devices, developed by the telecommunication industry, for signal analysis.
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| WEPC11 | FERMI@elettra Timing System: Design and Recent Synchronization Achievements | laser, linac, klystron, radio-frequency | 334 | ||
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FERMI@elettra is the fourth generation light source under construction at Sincrotrone Trieste. Being a seeded-FEL source, the requirements for the timing system are very tight as the final goal is a stable seeding process with sub-picosecond electron bunches and seeding laser pulses. Based on demonstrated results achieved in the main laboratories worldwide active in the field, like DESY, LBNL and MIT, an hybrid timing system scheme has been proposed which is currently under development. Both "pulsed" and "continuous wave (CW)" optical timing systems are being deployed, the choice being based on the differences among the different timing system clients; a Low Level Radio Frequency processor is a "quasi-CW" client whereas the lasers and some "longitudinal" diagnostics are "time discrete" clients. In this paper the FERMI@elettra timing system and the recent advances are presented. A pulsed optical clock has been locked to an ultra stable reference; its output pulses distributed over stabilized fiber optic links. As a benchmark client, a femto-second laser oscillator has been synchronized to the optical clock testing different possible schemes.
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| WEPC13 | Jitter Reduced Pump-Probe Experiments | laser, electron, target, photon | 337 | ||
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For two-colour pump-probe experiments carried out at the free electron laser FLASH@DESY, the FEL laser pulses in the XUV have to be synchronized with femtosecond precision to optical laser pulses (Ti:Sapphire). An electro-optical sampling diagnostic measures the arrival time jitter of the infrared pump-probe laser pulse in respect to the electron bunch of the FEL. Here, the electron arrival time is encoded spatially into the laser pulse profile and readout by an intensified camera. In this paper we report about the improvement of the temporal resolution of pump-probe experiments on gaseous and solid targets using the arrival time data acquired by the described EO-diagnostic.
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| WEPC23 | Progress of the Diagnostics at the Proscan Beam Lines | controls, quadrupole, emittance, kicker | 361 | ||
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PROSCAN, the dedicated new medical facility at PSI using proton beams for the treatment of deep seated tumours and eye melanoma, has entered the operational phase. Air and N2 filled ionisation chambers and secondary emission monitors in several configurations are used as current monitors, profile monitors, halo, position and loss monitors at the PROSCAN beam lines. The operation experience and improvements of these diagnostics as well as of the multi-leaf- and the standard faraday-cups and of the profile-evaluation technique are reported. Additional variants of ionisation chamber position monitors adapted to local requirements are now under construction. Criteria for interlocks which control beam parameters and the correct operation of diagnostics are discussed as well as dedicated procedures for checking the function of the built-in diagnostics. The fast exchange of beam-line components and spare parts are briefly mentioned.
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| WEO3A02 | Diagnostic Instrumentation for Medical Accelerator Facilities | ion, synchrotron, proton, linac | 381 | ||
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A number of accelerator facilities are presently emerging for the medical treatment of tumour patients using proton and light ion-beams. Both, the development of relatively compact accelerators and extensive studies on ion-therapy carried out at various accelerator laboratories were prerequisites for the layout of dedicated medical accelerator facilities. This paper focuses on the special demands for beam diagnostic devices during the commissioning and routine operation of a medical accelerator. The proton-therapy project PROSCAN at the Paul-Scherrer-Institute in Villigen/Switzerland exemplifies medical treatment in the frame of a research institute. As examples for dedicated ion-therapy projects the beam diagnostic layout is presented for the CNAO project (Centro Nazionale Adroterapia Oncologica) located in Pavia/Italy and the HIT facility (Heidelberger Ionen Therapie) in Heidelberg/Germany. Beam diagnostic devices of HIT are illustrated and the underlying concept for the type and precision of the devices is explained. Additionally, measurement results of the HIT linac and synchrotron commissioning are presented.
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