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| MOO2A02 | Electron Beam Diagnostics for the European X-Ray Free-Electron Laser | diagnostics, electron, emittance, laser | 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 | diagnostics, 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, diagnostics, 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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| TUPB10 | Proposed Beam Position and Phase Measurements for the LANSCE Linac | simulation, bunching, instrumentation, beam-losses | 78 | ||
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There is presently an ongoing effort to develop beam position and phase measurements for the Los Alamos Neutron Science Center (LANSCE) linac associated with an improvement project known as the LANSCE Refurbishment. This non-interceptive measurement’s purpose is to provide both beam measurements of phase for determining rf-cavity phase and amplitude set points, and position measurements for determining the 805-MHz linac input transverse position and trajectories. The measurement components consist of a four-electrode beam position and phase monitor (BPPM), a cable plant that transports the 201.25-MHz signals, electronics capable of detecting phase and amplitude signals, and associated software that communicates with a mature LANSCE control system. This paper describes measurement requirements, proposed beam line device and some initial device bench measurements, initial designs of the associated electronics, and some of the difficulties developing these beam measurements in an operational facility.
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| TUPB12 | BPMs for the XFEL Cryo module | quadrupole, cryogenics, pick-up, alignment | 84 | ||
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The European XFEL is based on superconducting accelerator technology developed in the context of the TESLA collaboration. The accelerator itself consist of cryo modules each equipped with 8 cavities, followed by a quadrupole/steerer package, a BPM and a HOM absorber. This contribution will present the layout of the BPM system for the cryo modules, describing the monitor itself, its integration into the cryo module. Additionally, the electronics concept will be discussed. Finally the results of beam measurements at FLASH using prototypes of the monitor and the electronics will be presented.
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| TUPB15 | Beam Position Monitors Using a Re-entrant Cavity | dipole, single-bunch, linear-collider, collider | 93 | ||
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Two designs of high resolution beam position monitor, based on a radiofrequency re-entrant cavity, are developed at CEA/Saclay. The main radio-frequency modes excited by the beam in the cavity are monopole and dipole modes. The first monitor is developed in the framework of the European CARE/SRF program. It is designed to work at cryogenic temperature, in a clean environment and to get a high resolution and the possibility to perform bunch to bunch measurements. Two prototypes with a large aperture (78 mm) are installed in the FLASH linac, at DESY. The other design with an aperture of 18 mm and a large frequency separation between monopole and dipole modes, as well as a low loop exposure to the electric fields is developed for the CTF3 probe beam CALIFES at CERN. It is operated in single bunch and multi-bunches. This paper presents the mechanical and signal processing designs of both systems. Simulation and experimental results will be discussed.
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| TUPB17 | Diagnostics for the CTF3 Probe Beam Linac CALIFES | diagnostics, electron, emittance, 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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| TUPC09 | Design of the cavity BPM system for FERMI@elettra | dipole, coupling, simulation, diagnostics | 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, 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, emittance, laser, 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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| TUPC19 | Matlab Code for BPM Button Geometry Computation | vacuum, storage-ring, booster, controls | 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.
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| TUPC26 | Button Beam Position Monitors for FLASH | undulator, pick-up, radiation, electron | 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.
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| WEO1A03 | Instrumentation for Longitudinal Beam Gymnastics in FEL's and in the CLIC test facility 3 | electron, diagnostics, 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, diagnostics | 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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| WEPB07 | Time Domain Diagnostics for the ISAC-II Superconducting Heavy Ion Linac | ion, electron, emittance, 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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| WEPB31 | Injector Diagnostics Overview of SPIRAL2 Accelerator | pick-up, diagnostics, ion, 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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| WEPC11 | FERMI@elettra Timing System: Design and Recent Synchronization Achievements | laser, klystron, diagnostics, 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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| WEPC14 | Segmented Beam Dump for Time Resolved Spectrometry on a High Current Electron Beam | electron, radiation, simulation, scattering | 340 | ||
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In the CLIC Test Facility 3, the strong coupling between the beam and the accelerating cavities induces transient effects such that the head of the pulse is accelerated twice as much as the rest of the pulse. Three spectrometer lines are installed along the linac with the aim of measuring energy spread versus time with a 20ns resolution. The major difficulty is due to the high power carried by the beam which imposes extreme constraints of thermal and radiation resistances for the detector. This paper presents the design and the performances of a simple and easy-to-maintain device, called ‘segmented dump’. In this device, the particles are stopped inside metallic plates and the deposited charge is measured in the same way as in faraday cups. Simulations were carried out with the Monte Carlo code ‘FLUKA’ in order to evaluate the problems coming from the energy deposition and find ways to prevent or reduce them. The detector resolution has been optimized by choosing the adequate material and thickness for the plates. The overall layout of the monitor is described with a special emphasis on its mechanical assembly. Finally, limitations arising at high beam energies are discussed.
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| WEPC19 | Toroid Protection System for FLASH | simulation, beam-losses, single-bunch, electron | 349 | ||
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The FLASH fast machine protection includes a beam loss interlock using toroids to measure the beam charge. This system monitors the beam losses across the whole linac while other protection systems are specifically dedicated to critical components. Four protection modes are used to handle different scenarios of losses: charge validation, single bunch, slice and integration modes. This system is based on 4 ADC’s to sample the top and bottom of upstream and downstream toroid signals. A microcontroller drives 2 programmable delay generators to adjust the top and bottom ADC trigger during the calibration phase. The samples are then collected by a 200Kgates FPGA to process the various protection modes. At first, a VHDL testbench was developed to generate test vectors at the FPGA design inputs. Then, an electronic testbench simulates the linac signals to validate the global hardware functions. Finally, the toroid protection was tested on FLASH with long bunch train at 1 MHz repetition rate.
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| WEPC21 | Diagnostics of the Waveform of Picosecond Electron Bunches Using the Angular Distribution of Coherent Sub-mmTransition and Diffraction Radiation | radiation, electron, target, vacuum | 355 | ||
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The spectra of sub-mm wavelength coherent transition radiation (TR) and diffraction radiation (DR) have previously been used to measure the bunch length of picosecond electron beam pulses. However, both the spectral and angular distributions of the radiation from a finite target or aperture with size r, are strong functions of the wavelength, when λ ≈ 2πr/γ where γ is the relativistic factor of the beam. This dependence must be taken into account in the determination of the bunch form factor and bunch shape. Also the spectral density of the bunch is a strong function of wavelength when λ ≈ d, the characteristic length of the bunch. When both the above conditions are fulfilled, i.e. λ ≈ 2πr/γ ≈ d, the spectral and angular distribution (AD) of the radiation are very sensitive to the longitudinal distribution of the bunch. We are investigating the use of the AD of TR or DR, to diagnose the bunch length and shape. Here we present a comparison of measured and calculated angular distributions from two targets: a solid disk and a rectangular slit, which we have used to determine the waveform of the beam bunch produced at PSI’s SLS pre-injector LINAC.
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| WEPC22 | Synchronization of a 3GHz Repetition Rate Harmonically Mode-Locked Fiber Laser for Optical Timing Applications | laser, feedback, polarization, controls | 358 | ||
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We have successfully stabilized a 3GHz Harmonically Mode-Locked fiber ring laser by a PLL feedback control of the cavity length to reduce the pulses RMS timing jitter. The laser cavity is composed of all PM fibers and components to eliminate polarization instabilities and to reduce the vibration sensitivity. The laser stability in terms of timing jitter was around 9ps in the range 10Hz-10MHz. Using a PLL scheme we synchronized the laser repetition rate to an ultra stable RF generator. The noise characteristics of the laser output were measured by observing the SSB noise spectra of the 1st harmonic, from 10Hz to the Nyquist frequency (1.5GHz). We have obtained a global reduction of fiber laser timing jitter value down to less than 100fs in the range 10Hz-10MHz; a complete overlapping between the laser and the RF generator spectral profiles in the loop bandwidth has been observed. An extended investigation has been performed to estimate the phase noise spectra and timing jitter up to 1.5GHz. By doing so, the contribution of the laser supermodes to the phase noise has been taken into account as well, to quantify the true value of the total RMS timing jitter of the optical pulses.
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| WEPC28 | Timing and Synchronization at the LCLS | laser, electron, klystron, controls | 373 | ||
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Timing and synchronization in the LCLS is a three tier process: At level 1 an event generator broadcasts timing fiducials to event receivers over a fiber network. Hardware and software triggers are created in the event receiver according to the digital pattern broadcast at 360 Hz by the event generator. Beam synchronous data acquisition driven by these triggers allows time-stamped acquisition of all diagnostic devices simultaneously on every pulse. Timing fiducials are phase synchronized to the low level RF reference system with 10 ps precision. Level 2 synchronization ensures that individual klystrons powering gun and accelerating sections remain within a few tenths of a degree S-band to the phase reference distribution scheme. The gun laser system is also phase locked to this reference to within 0.5 ps. Level 3 provides synchronization at the 10 fs level between the electron beam and pump-probe laser systems in the end station experiments. This will be achieved with electro-optic sampling of the electron bunch and by synchronizing the laser systems over a stabilized fiber distribution system. A fiber stabilization scheme is currently under test at Lawrence Berkeley Laboratory.
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| WEO3A01 | Low-Latency High-Resolution Single-Shot Beam Position Monitors | pick-up, feedback, dipole, alignment | 376 | ||
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In this paper design aspects of high-resolution, single-shot transverse beam position monitors (BPMs) are discussed. The focus is put on BPMs which can provide (sub-)micrometer precision at measurement speeds of less than a few hundred nanoseconds. Different pickups, analog signal conditioning electronics, and digital post processing schemes are reviewed. Their characteristics and limitations with respect to application in high-resolution, fast BPMs are pointed out. Exemplary implementations of successful BPM realizations found in the literature are reviewed. A specific implementation of a BPM based on a resonant stripline pickup, developed for a fast transverse feedback system for the European X-FEL, is also presented.
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| WEO3A02 | Diagnostic Instrumentation for Medical Accelerator Facilities | ion, synchrotron, proton, diagnostics | 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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