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| MOD1A01 | Digital EBPMs at Diamond: Operational Experience and Integration into a Fast Global Orbit Feedback | feedback, storage-ring, power-supply, controls | 24 | ||
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We present out experience with the Libera EBPM during the first months of operation at Diamond. Measurement noise and beam current dependence with beam are compared to earlier lab measurements. Where discrepancies between the performance in the lab and in the application are observed, the causes have been investigated. Furthermore, results of the integration of the EBPMs into a FOFB system are presented, including measurements of orbit motion spectra with and without FOFB.
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| TUO1A01 | Bunched Beam Stochastic Cooling for RHIC | kicker, proton, ion, beam-losses | 39 | ||
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Stochastic cooling is an effective and well-established accelerator technology for improving beam quality. However, stochastic cooling of high frequency bunched beam has always proved problematic. We have built a stochastic cooling system for heavy ions in RHIC that is used on bunched beam. The purpose is to counteract Intra-Beam Scattering and improve integrated luminosity. The chief technical challenge of bunched beam is the strong coherent frequency components in the beam that contaminate the Schottky spectrum. Technical solutions for overcoming this problem are described. Results from commissioning in one ring of RHIC are reported.
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| TUO1A03 | Beam Diagnostic Features of the ESRF Multibunch Feedback | feedback, kicker, diagnostics, 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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| TUPB03 | Precision Beam Position Monitor for EUROTeV | vacuum, electron, linear-collider, collider | 57 | ||
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For future linear colliders (ILC, CLIC) a new Precision Beam Position Monitor (PBPM) has been designed within the framework of EUROTeV. The design goals are a resolution of 100nm and an overall precision of 10μm, in a circular vacuum chamber of 6mm in diameter. The required bandwidth is 100 kHz-30MHz. The PBPM is based on an inductive type BPM which measures the image current in four electrodes located outside the vacuum tube, from which the position is derived. In this paper, the design of the PBPM is presented together with the first bench measurements, where twoμmovers and a rotational stage, installed on a vibration damped table, have been used to characterize the PBPM.
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| TUPB06 | First Tests with the Sis18 Digital BPM System* | acceleration, synchrotron, injection, instrumentation | 66 | ||
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In this paper we describe new approaches for BPM (Beam Position Monitor) measurements, needed in hadron accelerators which have strongly varying beam parameters, such as intensity, accelerating frequency and bunch length. After the data collection and offline evaluation in 2005, first FPGA implementations of algorithms were completed in 2006 and tested at SIS18 and CERN PS. Main aspect of the first tests was the proof of concept in terms of online calculation feasibility. This includes online calculation of the needed integration windows as well as the baseline restoration algorithms. The realization of the hardware and the data handling are discussed. Least squares techniques were used for parametric fitting to gain bunch signal properties which can be used to monitor beam position.
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*Founded by EU FP6-Design Studies |
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| TUPB09 | Digital Beam Trajectory and Orbit System, for the CERN Proton Synchrotron | acceleration, target, controls, synchrotron | 75 | ||
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A new trajectory and orbit measurement system using fast signal sampling and digital signal processing in an FPGA is proposed for the CERN PS. The system uses a constant sampling frequency while the beam revolution frequency changes during acceleration. Synchronization with the beam is accomplished through a numerical PLL algorithm. This algorithm is also capable of treating RF gymnastics like bunch splitting or batch compression with the help of external timing signals. Baseline correction as well as position calculation is provided in the FPGA code as well. After having implemented the algorithms in C and MatLab and tested them with data from a test run at the PS they have now been implemented in the FPGA for online use. Results of measurements on a single beam position monitor in the CERN PS and the SIS-18 at GSI will be presented.
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| TUPB12 | BPMs for the XFEL Cryo module | linac, quadrupole, cryogenics, 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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| TUPB16 | Optimization of the Linear-cut Beam Position Monitors Based on Finite Element Methods | simulation, coupling, cryogenics, quadrupole | 96 | ||
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This contribution presents simulations of the Beam Position Monitors (BPMs) for the FAIR project that were performed using CST Studio Suite 2006B. The linear-cut BPMs based on a metal-coated ceramics were considered as the only solution that meets the required mechanical stability under cryogenic conditions. The essential BPM features like position sensitivity or linearity of position determination were compared for two geometries. In these geometries, in both cases based on elliptically shaped ceramic pipe, the vertical and horizontal electrode pairs were either mounted subsequently in series or were spirally shaped and combined alternatively within one unit. It is shown that optimization of BPM design increases position sensitivity by more than a factor of two. The frequency dependence of the position sensitivity and an offset of electrical center of BPM in respect to its geometrical center were analyzed in the bandwidth of 200 MHz. In a frequency range up to 100 MHz (i.e. typical for the BPM applications) calculated variations of the displacement sensitivity are smaller than 1%; the careful design of a guard ring configuration allows keeping the offset consistent with zero.
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| TUPB19 | Signal Level Calculation for the PETRA-III Beam Position Monitor System | insertion, vacuum, controls, insertion-device | 105 | ||
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Starting mid 2007 the PETRA accelerator at DESY in Hamburg (Germany) will be converted into a new high brilliance light source. For measurement and control of the PETRA-III closed orbit with a resolution of better than 1 micrometer (rms) it is planned to install about 220 button type beam position monitors (BPMs). To guarantee a good performance of the BPM electronics, the button signals have to meet several criteria in time and frequency domain. Therefore signal levels for the monitor types included for installation have been estimated. The results of these calculations will be presented together with a comparison of monitor signals from accelerators in operation, and the expected position resolution will be discussed for a certain type of BPM electronics.
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| TUPB20 | Large Horizontal Aperture BPM and Precision Bunch Arrival Pickup | laser, electron, simulation, vacuum | 108 | ||
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The large horizontal aperture chicane BPM and the precision bunch arrival monitor at FLASH will be important tools to stabilize the arrival-time of the beam at the end of the linac. The pickups for these monitors will be paired with front-ends that sample the zero-crossing of the beam transient through the use of electro-optical modulators and sub-picosecond-long laser pulses delivered by the master-laser oscillator. The design of pickups for this front-end requires the consideration of the beam transient shape as well as the amplitude. Simulations and oscilloscope traces from pickups that use or will use the EOM based phase measurement and the expected limitations and benefits of each pickup are presented. In particular, the design for a 5 um resolution BPM with a 10 cm horizontal aperture is demonstrated in terms of its capability to measure the beam energy and its sensitivity to the shape and orientation of the beam.
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| TUPB21 | Experience with Libera Beam Position Monitors at DELTA | beam-losses, kicker, diagnostics, storage-ring | 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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| TUPB31 | The Beam Position System of the CERN Neutrino to Gran Sasso Proton Beam Line | target, radiation, controls, proton | 141 | ||
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The CERN Neutrino to Gran Sasso (CNGS) experiment uses 400GeV protons extracted from the SPS, which travel along 825 meters of beam line before reaching the CNGS target. This beam line is equipped with 23 BPMs capable of measuring both the horizontal and vertical position of the beam. The final BPM is linked to the target station and due to radiation constraints has been designed to work in air. This contribution will give an overview of the BPMs used in the tansfer line. It will also provide a detailed explanation of their logarithmic amplifier based acquisition electronics, which consists of an auto-triggered sequencer controlling an integrator, the A/D conversion and the Manchester encoded transmission of the digital data to the surface. At the surface the digital data is aquired using the Digital Acquisition Board (DAB) developed by TRIUMF (Canada) for the LHC BPM system. Results from both laboratory measurements and beam measurements during the 2006 CNGS run will also be presented.
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| TUPC08 | Quadrupole Transfer Function for Emittance Measurement | quadrupole, emittance, 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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| TUPC13 | The new Diode BPM system for ELETTRA | controls, vacuum, undulator, storage-ring | 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.
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| TUPC26 | Button Beam Position Monitors for FLASH | undulator, radiation, electron, linac | 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, linac, diagnostics, radiation | 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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| WEPB02 | Design of an Intra-Bunch-Train Feedback System for the European X-Ray FEL | feedback, kicker, dipole, electron | 232 | ||
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After joining the preparatory phase of the European X-ray FEL project, the Paul Scherrer Institute agreed in taking over responsibility for electron beam stabilization by developing a fast intra-bunch-train feedback (IBFB) system, which will be tested in its prototype version at the FLASH linac of the collaboration partner DESY. The proposed IBFB topology consists of two beam position monitors ("upstream BPMs") followed by two kicker magnets for each transverse plane and two more BPMs ("downstream BPMs"). By measuring the position of each bunch at the upstream BPMs and applying suitable transverse kicks individually to the following bunches, the architecture of the FPGA-based digital IBFB electronics (with a latency preferably below the bunch spacing of 200 ns and 1000 ns for the XFEL and FLASH) allows to damp beam motions up to hundreds of kHz. In addition to the FPGA-based feedback, DSPs enable adaptive feed-forward correction of repetitive beam motions as well as feedback parameter optimisation using the downstream BPMs. This paper gives an overview of the architecture and status of the IBFB subsystems being developed, like stripline BPMs, digital electronics and kicker magnets.
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| WEPB15 | A Sub-50 Femtosecond bunch arrival time monitor system for FLASH | laser, electron, feedback, polarization | 262 | ||
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A bunch arrival time monitor system using the future laser based synchronization system at FLASH has been developed. The signal of a beam pick-up with several GHz bandwidth is sampled by a sub-ps laser pulse using a broadband electro-optical modulator. Bunch arrival time deviations are converted into amplitude modulations of the sampling laser pulses which are then detected by a photo-detector. A resolution of 30 fs could be reached, with the capability towards sub-10 fs level. In this paper we describe the design of the optical system and we present recent results.
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| WEPB19 | Digital Analysis of Beam Diagnostic Noise | diagnostics, coupling, proton, instrumentation | 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, diagnostics, electron, 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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| WEPB28 | First Tests of the Transverse Multibunch Feedback at Diamond | feedback, damping, kicker, instrumentation | 295 | ||
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This paper describes the design and initial tests of the transverse multibunch feedback system under development at Diamond. The system is designed to damp instabilities up to 250MHz in both the vertical and horizontal plane. This will lead to an increase of instability thresholds which will permit a reduction of chromaticity and thus should improve dynamic aperture and life time.
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| WEPB30 | Current Status of the SQUID Based Cryogenic Current Comparator for Absolute Measurements of the Dark Current of Superconducting RF Accelerator Cavities | cryogenics, electron, shielding, controls | 301 | ||
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This contribution gives an overview on the current status of a LTS-SQUID based Cryogenic Current Comparator (CCC) for detecting dark currents, generated for example by superconducting cavities for the upcoming X-FEL project. To achieve the maximum possible energy the gradients of the superconducting RF accelerator cavities should be pushed close to the physical limit of 50 MV/m. The so-called dark current of the superconducting RF cavities at strong electric fields may limit the maximum gradient. The absolute measurement of the dark current in correlation with the gradient will give a proper value classify the cavities. The main component of the CCC is a LTS-DC SQUID system which allows us to measure extremely low magnetic fields, caused by extracted dark currents of RF cavities under test. For this reason the SQUID input coil is connected across a toroidal superconducting pick-up coil (inner diameter: about 100 mm) for the passing electron beam. A noise limited current resolution of 40 pA/sqrt(Hz) with a measurement bandwidth of up to 70 kHz was achieved. Design issues and the application for the CHECHIA cavity test stand at DESY as well as experimental results will be discussed.
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| WEPB31 | Injector Diagnostics Overview of SPIRAL2 Accelerator | diagnostics, 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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| WEPC02 | Developments at Elettra of the Electronics for the Bunch-Arrival Monitor | controls, monitoring, coupling, laser | 310 | ||
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Within the framework of the EUROFEL project, a task has been started in 2006 for a joint development of a Bunch Arrival Monitor (BAM), based on the original idea from DESY. ELETTRA is responsible for the development of the VME-controlled clock-delay board of the BAM system. A variable clock-delay circuit (a phase shifter) is required to adjust the acquisition sampling point of the pick-up-modulated optical pulses of the master-laser oscillator. Since the optical pulses have a repetition rate of 40.625MHz (54MHz in the future) and the acquisition sampling frequency is double of this value, the clock-delay module operates in the 80-120MHz frequency range. The clock timing jitter of the acquisition system greatly affects the measurements of the system: the output timing jitter from the clock-delay board should be less than 0.5ps-rms. Therefore, due to the very strict additive timing-jitter requirements, three phase shifter versions were designed, built and phase-noise evaluated. Low-pass-filter implementation achieved 563fs (at 283fs source jitter) of total-system timing jitter, integrated IQ multiplier 365fs (at 188fs of source) and passive IQ modulator 265fs (at 208fs of source).
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| WEO3A01 | Low-Latency High-Resolution Single-Shot Beam Position Monitors | feedback, dipole, linac, 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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