| Paper | Title | Page |
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| TUPC02 | Photo Injector Cathode Laser Beam Intensity and Pointing Position Diagnostics at PITZ | 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 %. | ||
| TUPC03 | Synchrotron Radiation Monitor for Energy Spectrum Measurements in the Bunch Compressor at FLASH | 150 |
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| Longitudinal bunch compression in magnetic chicanes is used at the Free-electron LASer in Hamburg FLASH for the generation of ultra-short electron bunches. A Synchrotron Radiation (SR) monitor has been installed behind the third dipole of the first bunch compressor to measure the energy and energy profile of the dispersed bunches. An intensified CCD camera records the emitted SR in the visible and enables one to select single bunches out of a bunch train. The performance of the system has been tested for different accelerator settings. The setup serves as a test bed for the European XFEL. | ||
| TUPC05 | Screen studies at PITZ | 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. | ||
| TUPC06 | Coherent Radiation Studies For The FERMI@Elettra Relative Bunch Length Diagnostics | 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. | ||
| TUPC07 | Design and Construction of the Multipurpose Dispersive Section at PITZ | 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.
[1] S. Khodyachykh, et al., Proccedings of the 28th International FEL Conference, Berlin (2006). |
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| TUPC08 | Quadrupole Transfer Function for Emittance Measurement | 162 |
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| Historically the use of the quadrupole moment measurement has been impeded by the requirement for large dynamic range, as well as the sensitivity of the measurement to beam position. In this paper we investigate the use of the transfer function technique in combination with the sensitivity and 160dB revolution line rejection of the direct diode detection analog front end to open the possibility of a sensitive emittance diagnostic that may be implemented economically and without operational complication, quasi-parasitic to the operation of existing phase-locked loop tune measurement systems. Such a diagnostic would be particularly useful as an emittance monitor during acceleration ramp development in machines like RHIC and the LHC. | ||
| TUPC09 | Design of the cavity BPM system for FERMI@elettra | 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. | ||
| TUPC10 | A transverse RF deflecting cavity for the FERMI@elettra project | 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. | ||
| TUPC11 | The Beam Diagnostics System for the FERMI@elettra Photoinjector | 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. | ||
| TUPC12 | FPGA based Frame Grabber for Video Beam Diagnostics | 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. | ||
| TUPC13 | The new Diode BPM system for ELETTRA | 177 |
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| A new Beam Position Monitor system has been developed at ELETTRA based on an envelope detector. It is a four channel system reading in parallel the four voltages from a button pick-up that adopts a wide-band Schottky diode. The analogue bandwidth of the currently implemented detector is <1kHz which has been adapted to the present application of the system, i.e. a fast beam position interlock to be installed on the ELETTRA storage ring. The upgrade of the ELETTRA BPM which is based on the Libera detector suggested us to add some redundancy on the fast position interlock in order to protect the vacuum chamber from wrong positions / angles of the beam. The data collection scheme, based on a single board computer for each straight section, is presented. Currently, the system has been installed and tested on all the ELETTRA undulator sections; the first running experience is here presented. | ||
| TUPC16 | Ultimate Resolution of Soleil X-Ray Pinhole Camera | 180 |
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| During the commissioning of the SOLEIL Storage Ring, beam emittances have been measured with an X-ray pinhole camera system. The evolution of the system and its performances are presented here. As a result of the excellent alignment of the ring magnets, the vertical beam size is smaller than expected, that led us to an effort towards improving the initial resolution of the instrument. A high sensitivity CCD camera allows us to select the harder X-ray part of the radiation which is a key element for resolution improvement. Finally an evaluation of the ultimate pinhole resolution is made for SOLEIL. | ||
| TUPC18 | New Type Photocathode for X-Ray Streak Camera of the 10-Fs Resolution | 183 |
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High current streak camera with new principle of operation* allowing to get resolution of the order of 10 fs in the frequency range both of visible light and x-ray is described. One of the key units of the camera is photocathode of spherical configuration with its surface radius of 10…100 micrometers. For creating the photocathode new technologies, developed and realized, are described. The results of the photocathode fabrication and investigations of its main features are presented and discussed.
* A. M. Tron, I. G. Merinov, T. Gorlov. New generation streak camera design and investigation. Proc. of EPAC 2006, p. 1175. |
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| TUPC19 | Matlab Code for BPM Button Geometry Computation | 186 |
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| Third generation Synchrotron Light Sources with vertical beam sizes down to few microns require beam resolutions on the submicron level. Study of different Beam Position Monitors (BPM) geometries has been done to reach such tight requirements. The used Matlab Graphical User Interface (GUI) is based on the simulation of a charged particle inside a selectable vacuum chamber type, computing the induced signal that it produces on the button feedthroughs. Needed parameters for the computation are the button electrode dimensions, vacuum chamber profile, electron beam current and measurement bandwidth. Output results from the GUI are the induced power on the feedthroughs, BPM sensitivity and intrinsic resolution of the analyzed geometry. As sensitivity and resolution are BPM geometry dependent terms, the Matlab GUI turned out to be an easy and fast way for first step geometry analysis. | ||
| TUPC20 | The SOLEIL BPM and Orbit Feedback Systems | 189 |
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| SOLEIL is a third generation light source built in France, near Paris. Its BPM system is important for machine studies and for delivering stable beams to the users. A beam stable to 1/10th of the dimensions requires submicron stability in the vertical plane. The monitors, anchored either to the girders or to the ground, are fixed points of the vacuum chamber. Bellows avoid transverse drifts due to mechanical stress. The electronics design was driven by combined efforts through an active communication between accelerator labs (SOLEIL at first, later joined by DIAMOND) and Instrumentation Technologies. The result is the “Libera Electron” beam position processor. It combines a 0.2μm rms resolution and micron level stability for beam delivery with accurate turn-by-turn measurements (3μm resolution at 0.8MHz) for machine commissioning and beam physics studies. It also features position interlock, tune measurement, and postmortem capabilities. A Slow Orbit Feedback for correcting low frequency drifts (0 to 0.1Hz) is currently in operation. The Fast Orbit Feedback to be implemented soon will suppress higher frequency perturbations up to 100Hz. | ||
| TUPC23 | Design of a Submicron Resolution Cavity BPM for the ILC Main Linac | 192 |
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| A high resolution Beam Position Monitor (BPM) is necessary for the beam-based alignment and feedback systems of the future international linear collider (ILC). We present the cavity BPM developed at Fermilab within ILC collaboration. This monitor will be operated at cryogenic temperature and rigidly attached to the quad magnet. The same cylindrical cavity is used to obtain the signals from both dipole and monopole modes excited by beam. Such a scheme makes the BPM more compact for placing it inside the magnet space and simplifying the signal processing. The dipole TM110 mode is utilized to measure pulse to pulse beam motion at a theoretical resolution of approximately 50 nm. In order to measure a single bunch trajectory within 300 ns timescale we use a resonant coupling to lower cavity Q-factor. The ceramic windows are brazed inside coupling slots for vacuum isolation and easy cavity cleaning. We will present a BPM detailed numerical study and analyze its tolerance requirements for submicron resolution. | ||
| TUPC24 | A Versatile Emittance Meter and Profile Monitor | 195 |
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| We present the design, construction and the first results of a new, versatile emittancemeter and profilemonitor for low-energy, multiply-charged ion beams. Both instruments share the same basic design, e.g. they fit on the same size vacuum flange and many parts can be exchanged. The central component of both instruments is a beam-imaging device, consisting of two multi-channel plates (MCP) in the chevron configuration followed by a phosphor screen. This combination transforms the two-dimensional beam-intensity distribution to a two-dimensional light-intensity distribution, which is imaged via a mirror and a lens system onto a CCD camera mounted outside the vacuum. The MCP, phosphor screen and mirror are mounted on a table which can be moved in and out of the beam. For emittance measurements the device is equipped with a pepperpot plate with a pattern of small holes in one direction, which is stepped through the beam in the orthogonal direction. The structure of the pattern can be adapted to the expected shape of the emittance. By taking images of the beamlets passing through the holes at a number of positions the full four-dimensional beam emittance can be reconstructed. | ||
| TUPC25 | Design and Calibration of an Emittance Monitor for the PSI XFEL Project | 198 |
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| Paul Scherrer Institute (PSI) intends to realize a compact X-ray Free Electron Laser (XFEL) by developing a high brightness, high current electron source. Field emitter arrays (FEA) in combination with high gradient acceleration promise a substantial reduction of transverse emittances by up to one order of magnitude compared to existing electron sources for XFELs. A flexible, high resolution emittance monitor based on the "pepperpot measurement techique" has been designed for this "low emittance gun" project at PSI. The realization and the calibration procedure of the monitor will be described in this presentation. | ||
| TUPC26 | Button Beam Position Monitors for FLASH | 201 |
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| Abstract: FLASH (Free Electron Laser in Hamburg) accelerates electron bunches to up to 750 MeV for producing intense, coherent, very short pulses of radiation. Various types of BPMs (beam position monitors) are installed in the facility: cavity and re-entrant-cavity BPMs in the accelerating cryo-modules and button and stripline BPMs in most of the room-temperature sections. The undulator section, where the FEL radiation is produced, is one of the most critical areas of the linac in terms of requirements on the position monitoring. Due to the tight space, button BPMs were chosen for this area. The electronics is based on the AM/PM principle. In the past couple of years these BPMs were commissioned and intensively studied. A few modifications have been made in the electronics, in order to deal with the small signals and the very high frequencies of the ultra-short bunches. In this paper the button-BPMs at FLASH will be presented. The studies made in the RF laboratory and the measurements made on the performance of the BPMs will be discussed. |