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| MOO1A02 | High Resolution Transverse Profile Measurement | laser, electron, synchrotron, photon | 1 | ||
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In many cases the performance of a particle accelerator is in large part defined by the transverse emittance of the beams. In most cases, like colliders and light sources (Synchrotrons or Free Electron Lasers), the quality of the final product, i.e. luminosity and brilliance, is directly linked to this parameter. For this reason many techniques and devices have been developed over the years for monitoring the transverse distribution of particles along accelerator chains or over machine cycles. Moreover modern designs of accelerators allow smaller size and/or higher current beams. New, more demanding, emittance measurement techniques have to be introduced and existing ones expanded. This presentation will review the different methods and the different instruments developed so far.
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| MOO1A03 | Review of Synchrotron Radiation based Diagnostics for Transverse Profile Measurements | radiation, optics, synchrotron, diagnostics | 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 | diagnostics, electron, 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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| TUPB07 | Electric -In-Air-X-Ray- Detectors for high Resolution Vertical Beam Position Measurement at the ESRF | feedback, diagnostics, dipole, vacuum | 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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| TUPB08 | Measurement of Vertical Emittance with a system of Six -In-Air-X-Ray- Projection Monitors at the ESRF | electron, photon, controls, shielding | 72 | ||
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The ESRF Storage Ring is now equiped with a system of 5 independent imaging monitors that measure the vertical emittance of the electron beam in the middle of the bending magnet through the very hard X-rays that fully traverse the 40mm thick Copper dipole absorbers and enter the free air space behind it. The tiny power that leaks through the absorber, and carried by X-rays of ~160KeV of very narrow vertical divergence, is simply projected onto a scintillator screen at ~1.8m from the source-point and imaged by optics & camera. These inexpensive and compact detectors are fully operated in free air and can be easily installed and maintained without any vacuum intervention. They now work reliably in routine fashion and have demonstrated their high precision and resolution of the ESRF’s vertical emittance. These results will be presented in this paper together with the underlying principles of the projection detector, aswell as the practical design solutions applied to obtain the high spatial resolution, to make the system resistant to the hostile radiation environment behind the absorber, and to reduce its sensitivity to stray signals generated at this point.
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| TUPB11 | A laserwire beam profile measuring device for the RAL Front End Test Stand | ion, laser, diagnostics, electron | 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, booster, quadrupole, diagnostics | 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 | diagnostics, electron, 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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| TUPB22 | Renewal of BPM Electronics of SPring-8 Storage Ring | storage-ring, betatron, controls, closed-orbit | 114 | ||
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The signal processing electronics of the SPring-8 Storage Ring BPM were replaced during the summer shutdown period of the year 2006. Since then, the new electronics have been put into operation for user experiment runs. The purpose of the renewal was to upgrade the performance of the position measurement system, i.e. the position resolution, speed of the measurement, etc. The position resolution of them in the real operation condition was estimated by using the stored beam in the same condition as the operations for user experiments, in the following way. The closed orbit distortions (COD) were repeatedly measured with the interval of 4 seconds in order to obtain the root mean square (r.m.s.) values of differences between two consecutive measurements. Since the obtained r.m.s. values included the intrinsic resolution of the position measurement system and the effect of the beam motion, the effect of the beam motion was separated from the obtained r.m.s. data by assuming that the effect of the beam motion was proportional to the betatron function values at the BPM locations. As a result, the intrinsic resolution was estimated to be 0.1μmeters.
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| TUPB23 | Design Considerations for Phase Space Tomography Diagnostics at the PITZ Facility | quadrupole, space-charge, electron, diagnostics | 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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| TUPB27 | Recent Results from the Electron Beam Profile Monitor at the Swiss Light Source | electron, synchrotron, synchrotron-radiation, optics | 129 | ||
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Two different methods of beam profile measurements using a) visible-to-UV range synchrotron radiation and b) X-ray synchrotron radiation have been realized in a single diagnostics beam line at the Swiss Light Source (SLS). In the visible-to-UV case the vertically polarized synchrotron radiation renders an image heavily influenced by inherent emission and diffraction effects of synchrotron radiation. This nevertheless turns out to be an advantageous influence when determining rms beam profiles below 10 μm. However, high-precision wave-optics based calculations of the synchrotron light characteristics need to be performed (SRW-code) to ensure correct interpretation of the measured profiles. The visible-to-UV branch has a few built-in features allowing numerous cross-checks of the SRW-model. Surprisingly, wave-optics based calculations are also applicable, and required, for the X-ray pinhole camera setup. We briefly discuss the advantage of applying two different measuring techniques at the same source point. In total, for standard user operation at the SLS, the beam line has helped to establish a vertical emittance below 10 pmrad.
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| TUPB29 | Experimental Optimization of the Cathode Laser Temporal Profile | laser, cathode, simulation, electron | 135 | ||
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Producing a flat-top temporal intensity profile of the cathode laser pulse is a key issue for the XFEL photo injector. The photo injector test facility at DESY in Zeuthen (PITZ) serves as a test bench for FEL photo injectors. The PITZ cathode laser contains a pulse shaper to produce flat-top temporal pulse profiles. Based on birefringent filters the pulse shaper includes four degrees of freedom to achieve a pulse profile with parameters closer to the required XFEL photo injector specifications (20 ps FWHM, 2 ps rise/fall time). A procedure for experimental temporal laser profile optimization is presented in this paper. The laser profile is measured using a streak camera. The four parameters - pulse length (FWHM), rise and fall time as well as modulation of the flat-top which are obtained from a flat-top fit of the measured profile - are used in the profile evaluation. Utilizing results of beam dynamics simulations for various cathode laser profiles a single value of the goal function – the expected emittance growth due to measured imperfections of the profile - can be obtained. The procedure of the goal function minimization has been implemented and tested at PITZ.
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| TUPB30 | Applications of IEEE-1394 and GigE Vision Digital Camera in the TLS | controls, diagnostics, radiation, 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 | diagnostics, 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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| TUPC05 | Screen studies at PITZ | electron, simulation, scattering, diagnostics | 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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| TUPC07 | Design and Construction of the Multipurpose Dispersive Section at PITZ | dipole, quadrupole, diagnostics, 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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| TUPC08 | Quadrupole Transfer Function for Emittance Measurement | quadrupole, pick-up, resonance, kicker | 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.
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| TUPC10 | A transverse RF deflecting cavity for the FERMI@elettra project | electron, linac, optics, diagnostics | 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 | diagnostics, 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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| TUPC24 | A Versatile Emittance Meter and Profile Monitor | ion, ion-source, heavy-ion, vacuum | 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.
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| TUPC25 | Design and Calibration of an Emittance Monitor for the PSI XFEL Project | electron, laser, acceleration, gun | 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.
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| WEO2A01 | Beam Diagnostics for the Front End Test Stand at RAL | ion, ion-source, vacuum, simulation | 218 | ||
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The Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL) is intended to demonstrate the early stages of acceleration (0-3MeV) and beam chopping required for high power proton accelerators, including proton drivers for pulsed neutron spallation sources and neutrino factories. The FETS ion source is required to produce a 60 mA beam in pulses up to 2ms long at up to 50 pps with an RMS emittance of 0.3 π mm mrad. A number of different diagnostic systems are currently under development to provide precise measurements of the H- ion beam. A pepperpot emittance measurement system, which is also capable of high resolution transverse beam density measurements, has been designed for use on the ISIS ion source development rig. This system is capable of sub-microsecond time-resolved measurements at a range of positions along the beam axis. Details are given of the improvements to the current design, including extensive tests on suitable scintillators and emittance and profile measurements are presented. Additionally, the designs of two different novel laser diagnostic systems for FETS are also presented.
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| WEO2A03 | Advanced Measurements at the SPARC Photoinjector | simulation, laser, electron, space-charge | 224 | ||
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The objective of the first stage of the SPARC commissioning was the optimization of the RF-gun setting that best matches the design working point and a detailed study of the emittance compensation process providing the optimal value of emittance at the end of the linac. For this purpose an innovative beam diagnostic, the emittance-meter, consisting of a movable emittance measurement system, was conceived and built. More than a simple improvement over conventional, though non-trivial, beam diagnostic tools this device defines a new strategy for the characterization of new high performance photo-injectors. The emittance meter allows to measure at different location along the beamline the evolution of important beam parameters both in longitudinal and in the transverse phase space such as beam sizes, energy spread and rms transverse emittances in a region where the space-charge effect dominate the electron dynamics. The quality and the amount of the data allowed a clear reconstruction of the phase space evolution. We report also the first experimental observation of the double emittance minima effect on which is based the optimized matching with the SPARC linac
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| WEPB07 | Time Domain Diagnostics for the ISAC-II Superconducting Heavy Ion Linac | linac, ion, electron, laser | 247 | ||
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The medium beta section of the ISAC-II superconducting linac has 20 bulk niobium quarter wave resonators and adds up to 20 MV of energy to the 1.5Mev/u and A/q<=6 ion beam injected from the ISAC-I accelerators. The commissioning of this new linac started April 2006 and the first radioactive beam was delivered to an experiment in January 2007. A standard array of ISAC diagnostics were added to the ISAC-II section to commission and tune the transport beamline and linac optics. In addition two new devices were developed: an ion implanted silicon detector measuring beam particles scattered from a gold foil and time of flight (TOF) monitors based on micro-channel plates. These are used both to tune the LINAC and to characterize the accelerated beams in the longitudinal phase space. The TOF monitors have the time resolution below 100ps, energy resolution of 0.1% and dynamic range spanning 6 orders of magnitude. Data acquisition and analysis is highly automatic and integrated into the EPICS based ISAC control system. Design of the monitors and first measurements will be presented.
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| WEPC04 | Transverse Feedback Development at SOLEIL | feedback, impedance, damping, betatron | 316 | ||
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The SOLEIL ring is planned to operate in both multibunch and high current per bunch modes. However, the small vertical chamber aperture around the SOLEIL ring enhances the transverse impedance both in its resistive-wall and broadband content, resulting in instabilities that appear at relatively low current compared to the desired values. A decision was therefore taken to install a digital bunch-by-bunch feedback system, with an aim to make it operational from the beginning of the user operation. The system implemented comprises components developed elsewhere, particularly the FPGA processor of Spring-8, chosen among different possible solutions. Using a BPM and a stripline in the diagonal mode, a single unit of the FPGA processor board has shown to successfully suppress resistive-wall and ion induced instabilities in either one or both transverse planes up to 300 mA. The paper discusses the system characteristics including striplines whose shunt impedance was maximised by keeping the coupling impedance small*, the obtained performance as well as future extensions to overcome the encountered limitations.
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* C. Mariette ID1209 |
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| WEPC23 | Progress of the Diagnostics at the Proscan Beam Lines | controls, diagnostics, quadrupole, 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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